The 14th international "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors (HSTD 14)

16 Nov 2025, 00:00 → 21 Nov 2025, 14:00 Asia/Taipei

2F, Activities Center (Academia Sinica)

The 14th international "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors (HSTD-14) will be held on November 16 - 21, 2025 at the Activity center of Academia Sinica , Taipei, Taiwan. The primary goal of this symposium is to bring together experts in the design, processing and applications of semiconductor tracking detectors for discussions of past experiences, lessons learned and new ideas in development.

Find more at the HSTD14 home. Proceed on "Registration" to participate.

Presentations:

1. all ORAL: 17+3 minutes, slides in 4x3, 16x9 etc

2. POSTER:  max 80x100 cm2

 

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Sunday 16 November

08:00 Time Table leaflet: https://www-hep.phys.sinica.edu.tw/~hstd14/HSTD14-abstract-timetable-1009b.pdf

08:20 POSTERs will be put up the whole symposium period

08:30 Q&A to authors of POSTERS will be in Coffee/Tea times

ALL Poster: #1-#30

Poster

1 Radiation Resistance of Ge-doped Multi-Mode Fiber for Optical Links in Collider Experiments

Optical links in collider experiments provide the advantage of high speed data transmission with low mass fibers over a distance of a few hundred meters. The radiation resistances of Ge-doped multi-mode fibers are investigated in ionizing dose with Co-60 Gamma-ray. Depending on the doping substances and fabrication technologies, the radiation induced attenuation (RIA) differs very much. Fiber types of telecom grades can have the Radiation Induced Attenuation (RIA) of 0.05~dB/m with the total ionizing dose of 300~kGy(SiO2). The dose rate dependence is compared for the RIA responses in 5 Gy/hr to 1.4~kGy/hr and recovery with the Co-60 source removed. The temperature dependence shows higher RIA at lower temperature tested in -15 to 45 oC. The annealing of radiation induced defects in a few hours compatible RIA disregard the dose rate and temperature.

Speaker: Prof. suen hou (academia sinica)

HSTD14_fiber_20251116_v2d.pdf

2 Allpix$^2$ simulations of irradiated 3D columnar-electrode sensors for 4D tracking

3D silicon sensors have demonstrated excellent radiation hardness since their first deployment in the Insertable B Layer (IBL) at ATLAS, paving the way for their integration into the innermost layers of ATLAS and CMS for the high luminosity upgrade. Besides being extremely radiation-hard, they also promise excellent timing performance. A timing resolution of about 30 ps has been reported for 3D columnar-electrode test structures, while 3D-trench electrode sensors can achieve resolutions as low as $\sim$10 ps even after the exposure to very high fluences.

Despite the remarkable results, the fabrication technology for 3D-trench electrode sensors is still under development. In contrast, the fabrication of 3D columnar-electrode sensors has reached its maturity, with the capability of producing large-area sensors ($\sim$4 cm$^2$) with high yield. To fully exploit this advantage, we have conducted an extensive study of 3D columnar-electrode sensors with various configurations---specifically, different pixel sizes and numbers of readout electrodes (i.e., 1E or 2E structures)---aimed at improving radiation hardness, enhancing timing performance, and reducing dead area. Simulation results show the timing performance of the sensors can be significantly improved by downscaling the pixel size and/or introducing additional electrodes. These advancements could be important for the VELO Phase-2 upgrade at LHCb, which requires 4D tracking capabilities under extreme radiation damage.

Based on the study, a new batch has been scheduled for production at FBK in 2025; dedicated irradiation and characterization campaigns will follow after on-wafer electrical tests. However, to support future layout optimization, it is crucial to study how different structures respond to radiation damage in the meantime. Through the help of TCAD and Monte-Carlo simulations (Allpix$^2$), this work focuses on evaluating the charge collection properties and timing resolution of various 2E structures, with particular attention paid to their performance after irradiation.

Speaker: Jixing Ye (University of Trento)

Abstract_HSTD_JixingYe.pdf

3 Design and Simulation of a Novel Bowl-shaped 3D sensor for proton therapy

Abstract: With the increasing demand for proton therapy and heavy-ion therapy, 3D sensor technologies with effective detection volumes comparable to cell sizes have become a key research focus. This paper proposes a novel design method for a bowl-shaped 3D sensor and conducts simulation studies on their performance. The device structure designed for proton therapy consists of an array of three bowl-shaped sensors approximately 20 μm in diameter, fabricated on an epitaxial silicon substrate with a 10 μm epitaxial layer and a heavily doped buried layer. The proposed 3D sensor avoids complex deep trench etching processes, offering high feasibility for practical implementation. Each pixel forms its intermediate electrode and edge electrodes through in-situ doping and protective ion implantation at a concentration of 1×1019 cm−3. A guard ring on the surface of each pixel is formed by ion implantation to optimize electric field distribution and prevent premature breakdown.

Electrical properties of the 3D sensor, including potential/electric field distribution, carrier concentration profiles, specific gravity fields, minimum ionizing particle (MIP) response current curves, and extracted rise times/collected charges, are investigated through TCAD simulations. Additionally, a fabrication process is proposed: starting with a substrate comprising a semiconductor base layer, a buried heavy doped layer, and a semiconductor top layer. Wet/dry etching forms spaced bowl-shaped structures. Electrodes and guard rings are then sequentially formed via in-situ and ion implantation doping. This design method lays a solid foundation for future device research in proton therapy, Lidar, and related fields.

Keywords: Novel Bowl-shaped 3D sensor; Electric field; MIP; Collected Charge; Fabrication process

Speakers: Jinxi Gu (Institute of Microelectronics of the Chinese Academy of Sciences (IMECAS), 100029, Beijing), Ms Manwen Liu (Institute of Microelectronics of the Chinese Academy of Sciences (IMECAS)), Mr Zheng Li (Institute of Microelectronics of the Chinese Academy of Sciences (IMECAS))

4 TCAD simulation of p-MCz Si LGAD equipped with MGR irradiated up to a mixed fluence of 1 x 1017 neq./cm2

Radiation hard LGAD as a MTD detectors requires for the 4D tracking with the process of assigning a space and a time coordinate to a hit -~10-30 μm position and ~10-30 ps time resolution in the CMS phase 2 of the experiment for HL-LHC upgrade and FCC colliders. To improve the performance of the heavily irradiated LGAD detectors up to the mixed fluence of 1 x 1017 neq./cm2 in terms of high fill factor with the reduced dead space without any avalanche breakdown, and full depletion voltage <800V is the crucial requirement for the detector to achieve the aforesaid criteria. In this contribution, TCAD simulation has been used to perform the full device optimization using surface and four level deep trap p-MCz mixed radiation damage model for the experiments and extrapolate the data taken into account the PerguiaModDoping acceptor removal model in the SRH and CCE modeling of the irradiated detectors for the data as per the experiment up to -400C. The electric field, electron concentration in the EAL layer and space charge distributions are shown inside the detectors around the trench and JTE extension to illustrate the reasons for the possible innovations and technological improvement in the gain of the irradiated LGAD devices.

Speaker: AJAY SRIVASTAVA (CHANDIGARH UNIVERSITY)

HSTD_Abstract17.pdf

5 TCAD Simulation of n-Fz Double Sided Silicon Microstrip Detector Irradiated by Protons for the R3B Experiment

Radiation hard n-Fz Double Sided Silicon Microstrip Detectors are used in the Silicon Tracker for the detection of two-dimensional position and energy loss measurement of the incident protons in the R3B experiment at FAIR, Darmstadt, Germany.
For the development of the detectors in the R3B Silicon Tracker, the macroscopic analysis is conducted on the available test structure of n-Fz Double Sided Silicon Microstrip Detector, which was fabricated by BEL, Bengaluru, India, and the SRH results on the non-irradiated test structure detectors are compared with the experimental data. The SRH and CCE modeling is used to extrapolate the results up to the proton fluence of 5-8×1014 neq cm-2 for the proton irradiated detectors. This experience is used in the designing of the Double Sided Silicon Microstrip Detector equipped with Wider Guard Ring design for the phase 1 upgrade of the experiment. The inner and the outer sides (towards the cut edge) of the detector are simulated by Silvaco ATLAS device TCAD tool to extract the electric field distribution inside the irradiated detectors.
Depending on the performance of the detector in the phase 1 radiation environment, this radiation hard 200 μm ac coupled Double Sided Silicon Microstrip Detector equipped with an intra guard ring and an outer edge wider guard ring structure has been proposed for the phase 1 upgrade of the R3B Silicon Tracker.

Speaker: Ms Puspita Chatterjee (Department of Physics, Chandigarh University, Mohali, Punjab, India)

HSTD-2025.docx

6 X-ray Response Characteristics of 3D Sensor with Concentric Ring Structure

Abstract: We propose a novel 3D detector with a concentric ring electrode configuration. Multiple columnar collecting electrodes are evenly distributed in the annular region between the central columnar electrode and the outermost annular trench electrode. The small potential saddle points generated between adjacent collection electrodes naturally isolate the signal. The annular trench electrode and the cylindrical trench electrode are alternately distributed to optimize the electric field distribution in the 3D detector, and the detection dead zone can be reduced by adjusting the electrode spacing. In this work, device simulation data from TCAD was used to investigate the X-ray incident response characteristics of the novel sensor after adjusting structural parameters, including electric field and potential distribution, transient induced current, and charge collection efficiency (CCE). We found that the device can withstand voltages in excess of 1,000 V without breakdown, has high reliability, and is fully depleted at a bias voltage of 67 V with low power consumption. The thicker substrate thickness enables efficient collection of 1-10 keV X-rays with a response time of less than 20 ns and a peak CCE at about 300 V.

Keywords: 3D Sensor with Concentric Ring Structure; X-ray incidence; Charge Collection Efficiency (CCE); Response time; Breakdown voltage

Speakers: Peng Xu (IMECAS), Manwen Liu, Zheng Li (Institute of Microelectronics of the Chinese Academy of Sciences (IMECAS))

7 CMS Phase-2 Inner Tracker for the HL-LHC Upgrade

The High Luminosity LHC (HL-LHC) aims to achieve instantaneous luminosities a factor of 5 to 7.5 larger than the nominal LHC value. In ten years of running, integrated luminosities of 3000 to 4000 fb−1 will be delivered to the CMS experiment. During Long Shutdown 3, the entire CMS tracking system will be replaced in preparation for the HL-LHC to mitigate the increased radiation and data rate. It consists of an Inner Tracker (IT) based on silicon pixel modules, and an Outer Tracker. The innermost part of the IT will be exposed to extreme conditions such as unprecedented radiation levels of up to Φeq = 2.6E16 cm−2 (after 3000 fb-1) and a hit rate of 3.2 GHz/cm2. New modules relying on novel technologies are designed for the IT, which are hybrid detectors consisting of CMS readout chips manufactured in 65 nm CMOS (RD53B_CMS) and silicon pixel sensors with a pixel size of 25 x 100 µm2 and a thickness of 150 µm, coupled via fine-pitch flip-chip bump bonding. A novel serial powering scheme and high-bandwidth readout system will support the upgraded modules, while lightweight carbon-fiber mechanics with two-phase CO2 cooling will ensure structural integrity. The design will extend the tracking coverage up to |η| ≈ 4. This contribution presents an overview of the CMS IT upgrade project, including the ongoing activities and status of the module production of all the IT subsystems.

Speaker: CMS Collaboration

8 Simulations of radiation-induced charge loss in ALICE ITS3 MAPS prototypes

The ITS3 upgrade of the ALICE experiment at CERN will introduce ultralight, bent monolithic pixel sensors using the TPSCo 65 nm CMOS process. This design reduces the material budget to 0.09% X0 per layer and the innermost layer radius to 19 mm, improving the impact parameter resolution by a factor of 2 for momenta < 1 GeV/c.
As part of the ITS3 R&D effort, multiple prototype sensors were developed
and characterized, with extensive testing conducted using radioactive sources, particularly 55-Fe. Unlike charge deposition from minimum-ionizing particles, 55-Fe X-ray spectra offer a more stringent probe of charge collection dynamics and subtle detector effects, but are correspondingly harder to model precisely.
Accurately reproducing these spectra indicates a deep understanding of the
sensor’s internal processes. Although the sensors have met the radiation hardness requirements of 4 x 10^12 1 MeV neq cm^−2, higher irradiation levels (up to 10^16 1 MeV neq cm^−2) lead to notable degradation in the 55-Fe spectral response, due to radiation-induced effects in silicon. To investigate this, simulations were carried out using TCAD for electric field modeling and Garfield++ for charge transport. This presentation
will highlight the simulation approach, its role in understanding sensor
performance post-irradiation, and will showcase the excellent compatiblity with experimental data.
These results not only support the ongoing optimization of sensor performance for ITS3, but also lay the groundwork for developing next-generation monolithic sensors capable of operating reliably in even harsher radiation environments.

Speaker: Isabella Sanna

HSTD_abstract_ISanna.pdf

ALL Poster: #31-54

Poster

9 High precision spectroscopic observation of gamma rays from thundercloud

Thunderclouds are known to emit minute-long gamma-ray bursts, commonly referred to as gamma-ray glows. These emissions are believed to originate from bremsstrahlung produced by high-energy electrons accelerated within the clouds. We conducted winter lightning observations in a mountainous area of Niigata, Japan, where thunderclouds are easily observable. Our detection system comprises various scintillation detectors, including BGO, CsI(Tl), SrI2(Eu), and a high-purity germanium (HPGe) detector, to search for line gamma-ray emissions such as nuclear gamma rays and pair annihilation lines (511 keV). 　On December 24, 2024, we observed a gamma-ray glow event lasting approximately three minutes. Radar data indicated the presence of rain clouds over the observation site during this period. Each detector recorded an increase in gamma-ray count rates. In addition to the enhancement of continuum emissions, we detected tentative line emissions between 200 and 600 keV. Although the event was relatively weak as a gamma-ray glow, the presence of line-like features suggests that future, more intense events may reveal clearer spectral structures.

Speaker: Jun Kataoka (Waseda University)

HSTD14_abstract_20250723.pdf

10 A 25 Gbps VCSEL Driving ASIC for Detector Front-end Readout

This paper presents the design and the test results of a 25 Gbps VCSEL driving ASIC fabricated in a 55 nm CMOS technology for detector front-end readout. This VCSEL driving ASIC is composed of an input equalizer stage, a pre-driver stage and a novel output driver stage. The input equalizer stage adopts a 5-step CTLE structure to compensate the high frequency loss at the PCB traces, bonding wires and input pads. It can boost maximum up to 5.8 dB at 18 GHz while providing a DC gain of 10.7 dB. To meet both the gain/bandwidth requirements and the area restriction, the pre-driver stage adopts the inductor-shared peaking technology and the active feedback structure. The total gain and the overall bandwidth of the pre-driver stage are better than 18 dB and 19.5 GHz at all process corners, respectively. The proposed output driver stage uses the double feedforward capacitor compensation, T-coil technique and the adjustable FFE pre-emphasis technique to improve the bandwidth. This VCSEL driving ASIC has been integrated in a customized optical module with a VCSEL array. Both the electrical function and the optical performance have been fully evaluated. The output optical eye diagram has passed the eye mask test at the data rate of 25 Gbps. The peak-to-peak jitter of 25 Gbps optical eye is 21.7 ps and the RMS jitter is 3.3 ps.

Speakers: Mr Di Guo (Central China Normal University), Mr Qiangjun Chen (Central China Normal University), cong zhao

A 25 Gbps VCSEL Driving ASIC for Detector Front-end Readout.pdf

11 Evaluation of the charge collection properties on the silicon strip detector of the LHC-ATLAS experiment

The LHC-ATLAS experiment have been operated since 2010, aiming for new particle searches, and precision measurements of the Higgs boson properties. The SemiConductor Tracker (SCT) is one of the most important subsystems in the ATLAS detector, which plays a key role in tracking and pT measurement for charged particles. Since SCT is located 30-50 cm from the beam pipe, it has been exposed to a radiation fluence of o(10^{13}) n_eq/cm^2 during about 15 years of operation.
The charge collection efficiency is one of the most important parameters of the SCT detector, because it is directly connected to hit efficiency. The charge collection efficiency was supposed to be significantly reduced by the radiation damage. However, since SCT has a binary readout, we were not able to measure the charge collection efficiency directly. We therefore established a method to evaluate it from the median charge obtained by analyzing the threshold scan data. During the threshold scan, SCT modules were divided into several groups in phi, and each group was assigned to different HV setting. This method enabled us to evaluate the HV dependence of the charge collection efficiency of the SCT while minimising impacts on the quality of the physics data. In this poster, the first attempts of the charge collection efficiency evaluation of SCT using 2024 and 2025 datasets will be presented, in comparison with sensor irradiation experiments from the sensor R&D.

Speaker: Sayuka Kita (University of Tsukuba)

PosterAbstract_SayukaKita_ATLAS_SCT.pdf

12 Investigation of Proton Irradiation Effects in n-in-p-MCz Thin Silicon Microstrip Detector up to the fleunce of 1 x 1017 neq./cm2 at FCC Experiment:TCAD Simulation and Experiments

Physicists around the world are looking for the high performance of position sensitive and advanced design detectors, which can be used in harsh radiation environment at Future Circular collider (FCC). According to RD50 collaboration, one of the leading candidates for the detector material is p-MCz silicon for the bulk. In this work, we have proposed an advanced four deep trap level proton irradiation model for p-MCz Silicon detector for the FCC fluence. A very good agreement is observed in the experimental data of full depletion voltage, TCAD simulation and SRH modeling. The effective introduction rate of deep level donor trap E(30K) is played in the model using SRH statistics for effective doping concentration which helps to mitigate the increase of full depletion voltage at very high fluence. The extrapolated values of full depletion voltage, leakage current and charge collection efficiency are shown up-to the fluence of 1 x 1017 neq/cm2 in thin detector using TCAD simulation, and the results are explained using the electric field distribution, and space charges distribution inside the heavily irradiated detectors.

Speaker: Deepali Tanwar (Chandigarh University)

papaer abstract2025 (1).docx

13 A low jitter 2.56 Gbps reference-less CDR ASIC in 55 nm for NICA Multi-Purpose Detector Project

Nuclotron-based ion collider facility (NICA) is a new accelerator complex designed at the joint institute for nuclear research (Dubna, Russia) to study properties of dense baryonic matter. The multi-purpose detector (MPD) is one of three detectors in NICA and it has been designed as a 4𝜋 spectrometer capable of detecting of charged hadrons, electrons and photons in heavy-ion collisions at high luminosity in the energy range of the NICA collider. The bi-directional serial optical data transceiver system is employed between the front-end and the back-end in the detector readout electronics. The low jitter clock data recovery (CDR) ASIC is one of the key components in the high-speed serial down link direction. It receives a pair of high-speed serial input data, recovers the clock signal from the data and resamples the input data at the same time. This paper presents the design and the test results of a low jitter 2.56 Gbps reference-less CDR ASIC for NICA MPD project. The CDR ASIC consists of an input equalizer stage, a bang-bang phase detector (BBPD), a charge pump circuit (CP), a low-pass filter (LPF), a LC voltage-controlled oscillator (LC-VCO) circuit and a SPI module. The input equalizer stage adopts a 5-step continuous-time linear equalizer (CTLE) structure to compensate the high frequency loss from the system level including PCB traces, bonding wires and pads. The CTLE boosts maximum up to 9.8 dB at 7 GHz while providing a DC gain of 4.7 dB. The BBPD is used to detect the phase difference between the input data jump edge and sampling clock. To obtain low leakage current and reduce dynamic mismatch, two feedback operational amplifiers are employed in the charge pump circuit. To obtain a reasonable frequency range and an optimized Q factor performance, the two-step capacitor tuning structure and the novel capacitor array unit are adopted in the LC-VCO circuit. The two-step (coarse-fine) capacitor tuning structure consisting of the varactors and the capacitor array is adopted in the LC-VCO.
The CDR ASIC has been fabricated in a 55 nm CMOS process. The phase noise test results show that the CDR ASIC outputs the 2.56 GHz clock with a phase noise of -110 dBc/Hz at 1 MHz offset and a rms jitter of 857 fs. The logic test results show that the recovered 2.56 Gbps data is correct and the BER less than 10−12 is achieved in all tests.

Speakers: Di Guo (Central China Normal University), Mr cong zhao

Reference-less CDR ASIC in 55 nm for NICA MPD.pdf

14 Recent application studies of INTPIX4NA SOIPIX detector based X-ray camera using SiTCP-XG 10GbE based high-speed readout system at KEK facilities

The SOIPIX (Silicon-On-Insulator PIXel) detector is a unique monolithic structure imaging device under development by the SOIPIX group, led by the High Energy Accelerator Research Organization (KEK).
We, the detector team at the KEK Photon Factory (PF), have developed an X-ray camera [1] using the INTPIX4NA SOIPIX detector [2].
The INTPIX4NA has a sensitive area of 14.1 x 8.7 mm^2, with 425,984 pixels arranged in an 832-column × 512-row matrix, and a pixel size of 17 x 17 um^2.
This detector provides high resolution and excellent sensitivity for low-intensity X-rays.
The readout system used in the X-ray camera was also developed at PF.
It is equipped with SiTCP-XG, a network controller implemented on an FPGA, which supports 10 Gbps Ethernet to enable high-frame-rate imaging at several hundred hertz.
We are currently investigating the application of this X-ray camera in several experiments at KEK.
In this report, we present some of these studies:
(1) Application to the optics of an X-ray zooming microscope using two Fresnel zone plates (FZPs) [3] at PF AR-NE1A.
(2) Application to a phase-contrast X-ray imaging system using a two-crystal X-ray interferometer [4] at PF BL-14C.
(3) Application to non-destructive detection of lithium in Li-ion battery electrode materials using muonic X-rays [5] at J-PARC MLF Muon D2.

[1] R. Nishimura, N. Igarashi, D. Wakabayashi, Y. Suzuki, K. Hirano and Y. Arai, X-ray imaging camera using INTPIX4NA SOIPIX detector with SiTCP-XG 10GbE based high-speed readout system, Nucl. Instrum. Methods Phys. Res. A, 1064, 169429, (2024).
[2] R. Nishimura, S. Kishimoto, T. Sasaki, S. Mitsui, M. Shinya, Y. Arai and T. Miyoshi, "INTPIX4NA" — new integration-type silicon-on-insulator pixel detector for imaging application, J. Instrum., 16, P08054, (2021).
[3] D. Wakabayashi, Y. Suzuki, Y. Shibazaki, H. Sugiyama, K. Hirano, R. Nishimura, K. Hyodo, N. Igarashi and N. Funamori, X-ray zooming microscopy with two Fresnel zone plates, Rev. Sci. Instrum., 93, 033701, (2022).
[4] A. Yoneyama, D. Takamatsu, T.-T. Lwin, S. Yamada, T. Takakuwa, K. Hyodo, K. Hirano, S. Takeya, Crystal-Based X-ray Interferometry and Its Application to Phase-Contrast X-ray Imaging, Zeff Imaging, and X-ray Thermography. Appl. Sci., 13(9), 5424, (2023).
[5] I. Umegaki, Y. Higuchi, Y. Kondo, K. Ninomiya, S. Takeshita, M. Tampo, H. Nakano, H. Oka, J. Sugiyama, M. K. Kubo and Y. Miyake, Nondestructive High-Sensitivity Detections of Metallic Lithium Deposited on a Battery Anode Using Muonic X-rays, Anal. Chem., 92, 12, 8194−8200, (2020).

Speaker: Ryutaro Nishimura (Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization)

15 A Low-Noise Analog Front-End Readout ASIC for High-Rate Applications in Pixel Detectors

This paper presents the design and implementation of an analog front-end readout chip tailored for silicon pixel detectors, aiming to meet the requirements of energy extraction and signal shaping under high event rate particle detection scenarios. Fabricated using the GSMC 130\si{\nano\metre} CMOS process, the chip integrates key functional modules including a charge-sensitive amplifier (CSA), a CR-CR shaper, an inverting amplifier, a peak holder, and an analog multiplexer. The CSA converts transient charge signals generated by incident particles into voltage signals proportional to the deposited energy, providing the initial signal amplification and conversion. The CR-CR shaper performs signal filtering and shaping, producing a pulse width of approximately 10 $\mu\mathrm{s}$. The inverting amplifier adjusts the signal polarity and amplitude, while the peak holder captures and retains the pulse maximum. A 4:1 multiplexer enables selection of CSA, shaper, inverter, or peak output for monitoring. The measurement results show that the chip exhibits good linearity and stable shaping performance in the dynamic range of 0-20ke$^-$. Under typical operating conditions, the chip consumes 20.8 mW of power and achieves an equivalent noise charge (ENC) of approximately 25.2e$^-$. The core circuit occupies an area of approximately 44\si{\micro\metre} $\times$ 46\si{\micro\metre}. These features endow the chip with superior energy resolution and dynamic range, making it suitable for front-end analog readout in high-resolution silicon pixel arrays, and applicable to integrated nuclear detection systems and X-ray polarization measurement missions.

Speaker: Chunlai Dong

16 A wide-range RO-based PLL for particle physics experiments

Frequency synthesizers are widely used in many applications. For instance, particle physics experiments such as the LHC operate at a 40 MHz system clock, while the proposed CEPC is expected to use 43.3 MHz. To accommodate such diverse requirements, a wide-range frequency synthesizer with flexible reference and synthesized clocks is essential. We present a phase-locked loop (PLL) based on a ring-oscillator voltage-controlled oscillator (VCO) fabricated in a 55 nm technology. The PLL comprises a phase detector (PD), a programmable charge pump (CP), a low-pass filter (LPF), a ring-oscillator voltage-controlled oscillator (ROVCO), buffers, dividers, and selectors.

Three versions of the VCO core have been implemented to compare clock performance. Each VCO core includes three delay cells and an output buffer. VCO1 features a single tuning band spanning 0.4 to 4.45 GHz. VCO2 employs a 3-bit control to divide the total range into eight sub-bands. VCO3 utilizes a combined tuning method, generating 16 sub-bands with a slightly narrower frequency range of 1.4 to 4.1 GHz. The use of sub-bands reduces the VCO gain (Kvco), with the maximum value decreasing from 6.46 GHz/V for VCO1 to 0.52~2.88 GHz/V for VCO2, and further to 0.81~1.12 GHz/V for VCO3. The phase noise varies from -105 to -96 dBc/Hz at 1-MHz offset, depending on the frequency. Additionally, selecting appropriate sub-bands ensures that the control voltage remains within an optimal operating range when the PLL locks to the target frequency.

The design employs a programmable pre-divider (M={1,2}), feedback divider (X=4×{2,3,…31}) and output divider (K={1,2}×{2,4,8,16}×{1,3,5,15}) to enable a broad frequency range. The final output frequency is determined by the equation: Fout=Fref[X/(MK)]. To accommodate the broad tuning range and diverse division factors, the loop bandwidth is programmable through adjustments to the charging current and LPF resistance, ensuring proper loop bandwidth and phase margin are maintained. Preliminary laboratory tests confirm correct functionality and performance, with comprehensive testing, including X-ray characterization, scheduled for completion in September. Detailed design and measurements will be presented.

Speakers: Mr Qingkang Wu (IHEP), Xiaoting Li (IHEP)

17 Dual-Layer Scintillator-Based Detector for Photon-counting Computed Tomography with Improved Spectral and Spatial Performance

Photon-counting computed tomography (PCCT) has recently emerged as the next-generation CT technology, offering multi-energy and low-dose imaging capabilities that provides significant advantages over conventional energy-integrating detectors. Especially, PCCT using CdTe-based semiconductor detectors has already entered clinical use.
However, several practical limitations remain. For instance, semiconductors are difficult to fabricate in thick layers, which limits detection efficiency for high-energy photons. Moreover, small pixel sizes (typically 0.2–0.4 mm) are required to read out high-count-rate signals in PCCT, due to slow mobility of electron-hole pairs. While CdTe offers excellent energy resolution, such fine spectral resolution is generally not required in material decomposition in current multi-color CT imaging based on 4-6 energy bins.
To address these issues, we propose a novel PCCT system employing a dual-layer scintillator detector. Scintillators can be easily manufactured with variable thicknesses and allow flexible multilayer configurations, providing high detection efficiency across a broad energy range. Our design features a thin front layer optimized for low-energy photon detection and a thicker rear layer for high-energy photons. To overcome the spatial resolution limitations typical of scintillator-based CT (~1 mm), we introduce sub-pixel shifts between the two layers to enhance resolution via super-resolution techniques.
We constructed a prototype dual-layer detector and conducted imaging experiments using contrast agent and resolution phantoms. The results demonstrated improved image quality across a wide energy range and enhanced spatial resolution compared to a single-layer system, validating the concept.
This study highlights the potential of dual-layer scintillator-based PCCT as a practical, low-cost alternative to CdTe-based systems, with performance suitable for advanced spectral and high-resolution PCCT imaging.

Speaker: Ryotaro Minagawa (Waseda University)

HSTD14_additional_material_v3.pdf

18 Development and Evaluation of a Large-Area Silicon Strip Detector for Inverse Kinematics Beam Experiments at RAON

We present the development and application of large-area silicon strip detectors for the ELARK experiment at RAON. The sensors, fabricated on 6-inch high-resistivity n-type wafers with a thickness of 500 μm, were used as ΔE detectors in a ΔE–E particle identification system. I–V measurements confirmed low leakage current and stable operation. Laboratory tests using Am-241 and Gd-148 alpha sources demonstrated excellent charge collection and energy resolution. Integrated into the full ELARK system, the detectors performed reliably during beam experiments.

Speaker: Hye Young LEE (IBS(Institute of Basic Science))

HSTD 14_Abstract_Strip_Sensor.pdf

19 Assessment of the Imaging Performance of the CITIUS High-Resolution Detector for Heavy Charged Particles and Neutrons

This paper presents an evaluation of the response and imaging performance of CITIUS - a high-speed X-ray detector developed for use at SPring-8 and SPring-8-II - when applied to heavy charged particles and neutrons. In the detection of heavy charged particles, imaging accuracy is primarily determined by the diffusion and drift of charges generated in the active layer, as well as the extent of charge sharing among pixels.

To evaluate the detector's response under high charge density conditions, we first conducted an experiment using monoenergetic alpha particles emitted from an Am-241 source. Subsequently, template fitting was applied to the measured cluster shapes to extract the back bias dependence of charge diffusion and pixel-level noise. Based on these results, a detector simulation model was developed to evaluate the spatial resolution for heavy charged particles and neutrons as a function of pixel size and noise level.

Speaker: Yoshio Kamiya (International Center for Elementary Particle Physics, The University of Tokyo)

251116_hstdCitiusAbst.pdf

20 Efficiency Simulation and Digital Periphery Optimization of COFFEE3 Chip and Beyond

Pioneering R&D in HVCMOS pixel sensors at the advanced 55 nm process, the COFFEE series prototypes are currently being developed for the Upstream Pixel tracker (UP) in the LHCb Upgrade II. COFFEE3, the latest prototype with two distinct readout architecture, was design and fabricated in 2025. Though featuring a small-scale prototype (3×4 mm2), COFFEE3 is designed to match the final full-scale sensor (~2×2 cm2), aiming for proof of concept. To ensure that COFFEE chip will be able to handle the particle hit density at UP, which are expected to reach ~ 100Mhz/cm2 at the most extreme position, simulations of both readout architectures were performed. This is achieved by implementing, in C++, behavioral modeling of the pixel array and digital periphery, and then injecting Monte Carlo input data at the front-end to simulate realistic conditions. This talk will report the simulated efficiency of both readout architectures under full-scale array conditions, and the hit loss occurring during the process from the generation of hit information within the pixel to its readout to the end of column (EoC) buffers, caused by pile-up effects under high hit density of the LHCb environment. One readout architecture demonstrates an efficiency exceeding 99% when the EoC's single read operation takes less than 100 ns. Beyond this, using the same methodology of C++ behavioral modeling combined with Monte Carlo data, we have optimized the arbitration algorithm to enable rational scheduling of transmission resources within the digital periphery, addressing UP's data compression format requirements and the bandwidth limitations of the chip's readout link. The outcomes of this work are intended to identify bottlenecks in on-chip data processing and transmission under the high hit-density environment, and to further optimize the chip architecture to satisfy the comprehensive performance requirements of this application.

Speaker: Ms Xiaoxu Zhang (Insitute of High Energy Physics, CAS)

ALL Poster: #55-70

Poster

21 Readout the scintillation light with the CMOS image sensor IU233N5-Z

Polarization observations of X-rays and γ-rays are an important method to investigate the radiation mechanisms of high-energy astrophysical sources. However, such observations are difficult to perform, and there are few observational examples. CMOS image sensors are detectors with superior spatial resolution compared to CCDs. CMOS sensors are sensitive to optical light through X-rays, but have limited sensitivity to γ-rays.On the other hand, scintillator detectors are sensitive to γ-rays but lack spatial resolution. However, recent research has focused on scintillators with excellent spatial resolution of several micrometers. By combining these detectors, it may be possible to detect the electron tracks resulting from the scattering and absorption of X-rays and γ-rays, thereby enabling the detection of X-ray and γ-ray polarization. In this study, we used the IU233N5-Z CMOS detector manufactured by Sony. The IU233N5-Z is a CMOS detector for optical light with the smallest pixel size of 1.12 µm square. The basic characteristics of the IU233N5-Z for X-rays were reported at HSTD13. In this presentation, γ-ray sources 137Cs and 241Am were irradiated onto a CsI(Tl) scintillator without a microstructure, and the resulting scintillation light was detected by the IU233N5-Z. At 662 keV for 137Cs, a change in image brightness was observed depending on the presence or absence of the source, confirming that the CMOS detector can detect scintillation light. Furthermore, by attaching a lens to the IU233N5-Z, it was possible to detect scintillation light generated by α-rays from 241Am and scintillation light generated by γ-rays separately.

Speaker: Taishu kayanoki (Hiroshima University)

22 TID Impact on IHEP-IME AC-LGAD Strip Sensors

AC-LGADs have been investigated widely due to their excellent time and spatial resolution, making them highly promising for future collider experiments. However, radiation exposure may damage the gain layer, thereby affecting the performance of AC-LGADs. We conducted a TID irradiation experiment on a 5.6 mm AC-LGAD strip designed by IHEP and fabricated by IME, and studied the electrical characteristics such as IV and CV under high-dose TID irradiation. Additionally, we investigated changes in spatial and time resolution using laser TCT and beta tests to evaluate the lifespan and expected operational performance of this type of detector.

Speaker: Weiyi Sun

23 Comparison of a Medipix3 Silicon Sensor Detector Response to X-rays and Electrons in the 5-30keV Energy Range

The Medipix collaboration was formed in the 1990s at CERN with the intention of adapting hybrid pixel detector technology to fields outside of high energy physics. Since then there have been four generations of the Medipix detector, and four generations of the closely related Timepix detector. Silicon is a common sensor material for detecting X-rays in the 5-30 keV energy range. The response of silicon sensor detectors to X-rays in this range is well studied and understood, but the response to electrons of similar energies is not well documented. This energy range corresponds closely with typical energies used in scanning electron microscopy, one of the areas in which Medipix has found experimental and commercial use. Medipix3 is unique in the field of hybrid pixel detectors as it includes a charge summing mode which mitigates the effects of charge sharing. The performance of the charge summing algorithm has also not been well studied when comparing x-rays and electrons.

This research presents a systematic comparison study of a Medipix3 silicon sensor detector to both X-rays and electrons in the 5-30 keV energy range. At these energies electrons will lose a significant portion of their energy in the entrance window, making backside contact geometry an important factor. Experimental results show a consistent difference in response to X-rays and electrons in this energy range, with the electron response trending towards that of X-rays as the energy increases.

Measurements were conducted using X-ray fluorescence and an electron mirror, in both single pixel and charge summing modes, as well as for three gain modes. Additionally, simulations have been performed using AllPix2 which show a similar response to experiment, and are being used to guide development of a detector optimized for low energy electron detection.

Speaker: Rory McFeely (University of Glasgow)

24 Time- and Spatially-Resolved X-ray Diffraction Using the Timepix4 Hybrid Pixel Detector

X-ray diffraction (XRD) is a fundamental tool for non-destructive analysis of crystalline materials. In this work, we present a novel method that exploits the advanced features of the newly developed hybrid pixel detector Timepix4 to achieve both time- and spatially-resolved XRD.
Timepix4, developed by the Medipix collaboration, offers a sensitive area of 7 cm² composed of 512×448 pixels, each 55×55 µm² in size. It supports both traditional frame-based acquisition and a data-driven mode, where each pixel hit is read out independently. In this mode, the detector delivers energy measurements with a resolution around 1 keV, along with time-of-arrival information with a precision of up to 200 ps.
We utilize these capabilities to perform energy- and time-resolved XRD using a polychromatic X-ray source. This approach significantly simplifies the experimental setup by eliminating the need for monochromatic beams, while enabling high-throughput measurements and providing additional structural insights across multiple energy channels.
Our setup includes a standard off-the-shelf X-ray tube with a tungsten collimator to generate a fan-shaped beam. Experiments were performed on a phantom composed of multiple materials with well-characterized crystalline structures. To demonstrate the time-resolved capabilities, the sample was moved using a translation stage to simulate structural changes. The measured data were processed to extract scattering information from individual crystal planes intersected by the fan beam, including the interaction time and spatial location within the specimen. Analysis of the resulting data confirmed the ability to resolve lattice parameters dynamically in both space and time.
Achieved results demonstrate the potential of Timepix4 for advanced non-destructive testing and dynamic structural analysis using XRD, opening new possibilities in time-resolved diffraction experiments.

Speaker: Ondřej Urban (University of West Bohemia)

25 Investigation of interstrip resistance and charge collection properties of the ATLAS18 strip sensor for HL-LHC ATLAS using 1 cm^2 mini-strip sensors

Towards high-luminosity operation of the Large Hadron Collider (HL-LHC), starting in 2030, the inner detector of the ATLAS detector will be replaced by a fully-silicon-based inner tracker (ITk). The outer part of the ITk detector consists of $\sim$ 20,000 strip sensors with glued-on hybrids carrying the front-end electronics necessary for readout. A production version of the sensor (ATLAS18 design version) has a dimension of 9.8$\times$9.8 cm$^2$ with a strip pitch of 75.5 $\mu$m for barrel sensors, while endcap sensors have similar but slightly modified dimensions depending on the regions on the detector. During mass production, their electrical parameters are monitored after exposure of up to 1.6$\times$10$^{15}$ $n_\mathrm{eq}$/cm$^2$ or 660 kGy. This is done on a sampling basis for every batch (~ 40 wafers). Irradiation tests are performed as part of quality assurance (QA) using test structures, processed on the same wafer with the main sensor.
While the aforementioned QA programme with the test structures is being advanced to efficiently determine quality of the delivered main sensors and make a decision for their acceptance, detailed measurements of the production sensor properties provide important reference data for future operation of the ITk detector at HL-LHC, where only digitised data from the ITk strip detector are recorded in the data storage. We therefore emphasised studies of the following key parameters: interstrip resistance and charge responses to minimum-ionisation particles, using the mini-sensor with exactly the same strip structure as the main sensor but scaled down to 1$\times$1 cm$^2$. Irradiation tests were performed using 70 MeV proton beams at RARiS, Tohoku University, Japan. In addition to the standard laboratory measurements with radioactive sources, testbeam experiments were performed using 3 GeV electron beams at PF-AR Test Beam Line, KEK, Japan, to measure charge collection efficiency (CCE) using minimum-ionising particles (MIPs). From these measurements using several mini sensors, we found that the actual interstrip resistance is in the range of 200-300 MΩ, which is sufficiently higher than the bias resistance connecting between the strip and the bias ring, and CCE measured using MIPs well agrees with that from radioactive sources. In this presentation, these results are discussed in comparison with data from the QA tests.

Speaker: Shigeki Hirose (University of Tsukuba)

26 Measurement of p-Stop Density Variation in ATLAS18 Silicon Strip Sensor Wafers and Analysis Using TCAD Simulations

A total of 24,010 AC-coupled silicon strip sensors, consisting of n-type strips in p-type silicon and referred to as ATLAS18, are currently in production for installation in the upgraded ATLAS Inner Tracker (ITk). In n-in-p strip sensors, a dense p-type region (e.g., p-stop implant) is essential for electrically isolating the n-type strips from a conductive inversion layer between the strips caused by positive interface charges. The punch-through protection (PTP) structure is implemented at the end of each strip to protect the AC-coupling capacitor in the event of large currents flowing into the strips, despite the presence of the p-stop implant. During quality assurance (QA) testing, we occasionally observed a deviation in the threshold voltage ($V_{PTP}$) of the PTP structure in the test chips located at a corner of the wafer perimeter, with a shift of four standard deviations or more below the mean. To evaluate the variation of $V_{PTP}$ across a wafer, we selected two main sensors, each processed in a different furnace, where $V_{PTP}$ measurements in the QA test chips were still near the mean value. One sensor exhibited a flat distribution of $V_{PTP}$ measurements, while the other showed a non-uniform, parabolic distribution, with a shift of 4 standard deviations toward the wafer edge. TCAD simulations were used to analyze $V_{PTP}$ as a function of p-stop density, confirming that the $V_{PTP}$ is a good representation of the p-stop density. We set the nominal p-stop density ($4\times10^{12}$ cm$^{-2}$) to correspond to the mean $V_{PTP}$ value. The p-stop density at the wafer edge, which is four standard deviations away from the mean, is estimated to be approximately half ($2\times10^{12}$ cm$^{-2}$). A p-stop density of $2\times10^{12}$ cm$^{-2}$ should still be sufficient to ensure isolation, even in the presence of interface charges as high as several times $10^{11}$ cm$^{-2}$.

Speaker: Yoshinobu Unno (KEK)

27 Evaluation of Subpixel Response of the HV-CMOS Pixel Detector AstroPix3 with 500 μm Square Pixels

All-sky observations of MeV gamma rays are expected to play a crucial role in solving unresolved questions in high-energy astrophysics, such as the emission mechanisms of gamma-ray bursts and blazars. To that end, we propose an MeV gamma-ray mission concept, AMEGO-X. The gamma-ray detector onboard AMEGO-X consists of a silicon tracker and a CsI calorimeter. The silicon tracker is composed of an active target detector called AstroPix, which is currently under development and is expected to feature low power consumption (< 1.5 $mW$/$cm^2$) and a large depletion depth (500 $\mu m$) compared to other sensors. The third version of this sensor, AstroPix3, has a large pixel size of 500 × 500 $\mu m^2$ compared to other pixel sensors. Its depletion depth is estimated to be about 70 $\mu m$ under a bias voltage of 200$ V$, and it is important to investigate the distribution of the depletion depth in detail. However, such investigations have not yet been conducted. To address this, we conducted a scanning test using a collimated X-ray beam, generated from radioisotope source, which had a spot size of approximately $\sigma \sim$180 $\mu m$ on the sensor surface. The beam scanned across the chip in both horizontal and vertical directions at 100 $\mu m$ intervals, aligned with the pixel grid. As a result, we observed a Gaussian-like distribution of count rates within individual pixels. Furthermore, a Monte Carlo simulation based on Geant4 showed that the shape of the simulated count rate distribution closely matched the experimental data.
In this work, we report on the X-ray scanning evaluation of the AstroPix3 chip and comparisons with the results of the Monte Carlo simulations.

Speaker: Norito Nakano (Hiroshima Univ.)

28 TiO2 Based Deep UV Photodetector with Fast Response Characteristics

UV photodetectors are essential tools in the detection and quantification of UV radiation for a wide array of scientific and practical uses. These applications include disinfection and sterilization, ozone level monitoring, water purification, secure communications system and marine navigation. Thus, UV photodetectors play a key role in a variety of systems spanning health, defense, communication technologies, and space-based platforms, where they enable interference-free communication and high-speed optical pulse detection. Titanium dioxide (TiO2) is emerging as promising wide bandgap material for such UV detection applications. It exhibits a wide bandgap, enabling visible-blind UV detection. TiO2 has excellent chemical and thermal stability, low dark current, and rapid photo response. These attributes make TiO2 ideal for developing compact and energy-efficient UV photodetectors suitable for harsh environments. In this work, we present a simple and scalable approach to fabricate TiO2 based photodetectors using the thermal oxidation technique. The film characterizations that we have done include XRD (X-ray diffraction), LRS (Laser Raman spectroscopy), SEM (scanning electron microscopy), and UV-Visible spectroscopy. We have fabricated photodetectors of metal–semiconductor–metal (MSM) geometry, with Ti/Au contacts for signal acquisition. We perform electrical characterization through dark current–voltage (IV) measurements and evaluate the device response under a pulsed 266 nm laser with a pulse width of 0.5 ns. The detector shows fast and stable photoconductive behavior under deep UV illumination, demonstrating its suitability for applications in biological monitoring, space-based sensing, and strategic radiation detection.

Speakers: Dr Parushottam Majhi (Indian Institute of Technology Bombay), Rupa Jeena (IIT Bombay)

29 Removal of ring artifacts in cone-beam computed tomography using a specific-artifact detection and correction scheme

Gain variations of detector pixels in cone-beam computed tomography (CBCT) may lead to streaking artifacts in sinogram and ring artifacts in reconstructed CBCT images. Such gain variations can be mainly caused by inconsistent response of detector pixels owing to their defects and aging. This study presents an effective method to identify and correct streaking artifacts in sinogram using a specific-artifact detection and correction scheme for obtaining artifact-free projections, followed by the filtered-backprojection reconstruction. In the proposed scheme, the total variation of the artifact-contaminated sinogram is minimized with two l1-norm-based sparsity constraints of the artifacts using a primal-dual hybrid gradient-based optimization process. To verify the efficacy of the proposed approach, we conducted a semi-experiment on a clinical CBCT projections emulated with various detector pixel gain variations in the range of 5‒98% of normal detector gain and investigated the image quality. According to our preliminary results, the proposed method significantly reduced streaking artifacts in sinogram and thus ring artifacts in CBCT images, demonstrating its effectiveness. More systematic and quantitative results will be discussed in the presentation.

Speaker: Hyesun Yang (Yonsei university)

2025_HSTD_Hyesun Yang_Summary.pdf

30 Design and Performance Evaluation of a Filter-Free Dual-Layer Flat Panel Detector Using Monte-Carlo simulation

Dual-energy X-ray imaging utilizing a dual-layer flat panel detector (DE-FPD) is widely used in radiography and computed tomography. A conventional DE-FPD is composed of a top layer featuring a 200 μm-thick cesium iodide scintillator and a bottom layer with a 600 μm-thick scintillator, both connected to an identical amorphous silicon thin-film transistor array. These layers are separated by a 1 mm-thick copper (Cu) filter, which enhances spectral separation to improve dual-energy images. However, the Cu filter reduces the number of entrance photons reaching the bottom layer, significantly diminishing the quality of selective dual-energy images. This study introduces a filter-free DE-FPD design, incorporating a thicker (500 μm-thick) top layer scintillator, and evaluates the detector's performance using Geant4 Monte Carlo simulation. The performance was assessed by measuring the modulation transfer function, noise power spectrum, and noise-equivalent quanta for both the top and bottom layers under RQA5 and RQA7 X-ray beam quality. Our preliminary findings suggest that the proposed DE-FPD exhibits improved detector performance compared to the conventional model. More systematic and quantitative simulation results will be presented in the paper.

Speaker: Jiyong Shim

31 Evaluation of Performance of the p-stop Process Splits in ATLAS18 strip sensors, Pre- and Post-Irradiation

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC), foreseen for 2030, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). Radiation-hard $n^+$-in-$p$ micro-strip sensors developed for use in the ITk will be exposed to a total radiation fluence of up to $\Phi_{eq} = 1.6 \times 10^{15}$ 1 MeV $n_{eq}/cm^2$ and a total ionizing dose (TID) of 66 Mrad, both including a safety factor of 1.5. Under such extreme radiation conditions, maintaining high interstrip isolation is essential in ATLAS ITk silicon strip sensors to minimize charge sharing and suppress readout noise, thereby ensuring optimal spatial resolution in particle detectors.

During quality control (QC) and quality assurance (QA) procedures performed on ATLAS18 production sensors and test chips, ATLAS ITk sensor institutes identified instances of insufficient interstrip isolation in certain production batches. To investigate the origin of these issues and to try some technological improvements, the manufacturer, Hamamatsu Photonics K. K. (HPK), produced two dedicated sample batches containing main sensors and test structures with four variations of the p-stop fabrication process. These process types (1–4) were systematically evaluated by the ATLAS ITk strip sensor community to determine their effectiveness and uniformity. In total, 56 full-size sensors, along with numerous miniature sensors and test chips, were tested. A number of samples were used in the irradiation campaign reaching the maximum expected levels for the HL-LHC operation after 10 years - with neutrons up to $1.6 \times 10^{15}$ $n_{eq}/cm^2$, and with gamma rays from a $^{60}$Co source up to 66 Mrad.

The goal of this evaluation program is to assess the impact of fabrication process variations on interstrip isolation performance and provide feedback to HPK for future sensor development. The results show good sensor quality for all p-stop types, with no observed impact on early breakdown behavior in IV tests. Although differences in punch-through protection behavior were noted, all samples remained within QC specifications before and after irradiation. Type 4 sensors showed the most uniform punch-through voltage ($V_{PT}$) distribution pre-irradiation and the highest $V_{PT}$ values post-irradiation, suggesting stronger effective p-stop doping. Interstrip resistance ($R_{int}$) decreased with radiation dose but remained above specification for all types, with type 2 showing the highest post-irradiation $R_{int}$. These findings confirm the reliability of the evaluated p-stop designs and indicate specific advantages that can guide future sensor optimization.

Speaker: Jana Kozakova (Institute of Physics, Czech Academy of Sciences)

32 Solving the Sensor Cracking in ITK Strips

ATLAS is currently preparing for the HL-LHC upgrade, with an all-silicon Inner Tracker (ITk) that will replace the current Inner Detector. The ITk will feature a pixel detector surrounded by a strip detector, with the strip system consisting of 4 barrel layers and 6 endcap disks.
The basic building block of the ITk Strip detector is the “module,” composed of front-end electronics glued to a silicon microstrip sensor. A critical problem was encountered during pre-production of ITk Strip modules when it was found a significant fraction of silicon sensors cracked due to thermal stresses when glued to local support structures and brought to cold operating temperatures.
A taskforce was established, and an extensive program of simulations, test setups and research arrived at 2 possible solutions. The use a stress-relieving layer (interposer) into the module assembly process, and the optimisation of glue patterns.
Results from the taskforce, including simulations, radiation studies and quality control testing are shown for modules and their loaded local supports. These solutions have allowed the recommencement of Strip Module production.

Speaker: Andrew Blue (University of Glasgow)

ALL Poster: #71-100

Poster

33 Whole-body imaging of mice administered At-211 using a high-resolution X-ray and gamma-ray camera for small animals

In recent years, targeted radionuclide therapy (TRT) using alpha-particle–emitting radiopharmaceuticals, such as $^{211}$At, has attracted attention. To confirm the therapeutic efficacy of these agents, it is important to visualize the distribution of $^{211}$At in the body with high accuracy. In animal experiments, $^{211}$At imaging is typically performed using clinical SPECT systems designed for human imaging, which have a typical spatial resolution of approximately 5-10 mm. However, because small animals are much smaller than humans, it is desirable to establish an inexpensive and easy-to-use imaging device that provides an order-of-magnitude higher resolution, while still allowing whole-body imaging.

Therefore, we developed a high-resolution X-ray and gamma-ray camera with a $10 \times 10\ \mathrm{cm}^2$ imaging area specifically designed for mouse imaging and conducted animal experiments. This detector consists of four approximately $5 \times 5\ \mathrm{cm}^2$ MPPC (Multi-Pixel Photon Counter) arrays, a 0.5 mm-pitch diced GAGG scintillator, and a $\phi\,$98 mm tungsten parallel-hole collimator with the same pitch.

Using this device, $^{211}$At-NaAt or $^{211}$At-AuNPs were administered via the tail vein of anesthetized mice, and images were acquired targeting the 79 keV X-rays emitted by $^{211}$At. To further improve resolution, subpixel shift method was applied. This method involves overlaying images acquired at the initial position and a slightly shifted position, averaging the overlapping areas, halving the pixel size and improving resolution without changing the detector configuration. This method was applied to images taken after sacrifice, when the radiopharmaceutical distribution was no longer changing. As a result, accumulation of $^{211}$At in the stomach, thyroid, salivary glands, and bladder was confirmed with a high resolution of 0.25 mm pitch.

Speaker: Ms Yuka Kikuchi (Waseda University)

HSTD_attachment.pdf

34 Design and characterization of a prototype front-end readout ASIC for gas pixel detectors

Gas pixel detectors are widely used in X-ray polarization measurements due to their high spatial and energy resolution. To support the development of next-generation large-scale gas pixel detectors, we designed and fabricated a prototype front-end readout ASIC using the GSMC $130\,\mathrm{nm}$ CMOS process in 2025. This custom ASIC integrates a $2 \times 2$ pixel array with a pixel pitch of $35\,\mathrm{\mu m} \times 45\,\mathrm{\mu m}$, occupying a total area of $70\,\mathrm{\mu m} \times 90\,\mathrm{\mu m}$. Each pixel consists of a charge collection electrode, a charge sensitive amplifier (CSA), a peak detect and hold (PDH) circuit, a two-stage buffer, and configuration logic. Four pixels are grouped into a $2 \times 2$ pixel block, which also serves as a basic triggering unit. We describe the design methodology and present measurement results of the prototype. The pixel achieves a charge-voltage conversion gain of $60\,\mathrm{\mu V/e^-}$, a full dynamic range of approximately $25\,\mathrm{k\,e^-}$ with a nonlinearity below 5%, and an equivalent noise charge (ENC) of about $50\,\mathrm{e^-}$. These results validate the pixel design and provide guidance for future integration into large-scale detector arrays.

Speaker: Zhuo Zhou

35 An initial study of in vivo imaging using two-dimensional SiPM-based photon-counting CT system

Photon-counting computed tomography (PC-CT) is a next-generation imaging technology that enables material discrimination and localization with K-edge imaging by detecting individual X-ray photons along with their energy information. In a previous study, we developed one-dimensional PC-CT system consisting of multipixel photon counters (MPPCs) and yttrium-gadolinium-aluminum-gallium garnet (YGAG) scintillators with a matching 1 × 64 pixel size. This system successfully demonstrated material discrimination and concentration estimation in an object. However, the one-dimensional detector has a limitation in acquisition speed, making it impractical for medical applications.
　In this study, we developed a two-dimensional PC-CT system employing a 1024-channel pixel array detector, composed of 16 × 64 pixels to realize fast and dynamic imaging. Signals from the MPPC are processed by an originally developed LSI whose performance has been validated through experiments with the one-dimensional PC-CT system. Performance evaluation revealed an average energy resolution of 40.7±2.1 % (FWHM at 59.5 keV) over the 1024 channels, and a count rate tolerance of 4.4±0.2 MHz, which are equivalent to those of the one-dimensional system.
　Furthermore, as a preliminary experiment for application to dynamic imaging, in vivo imaging of mice injected with a gadolinium-based contrast agent, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB), was performed. The imaging time was drastically reduced to ~1/10 of that of a one-dimensional system, demonstrating the feasibility of dynamic imaging. We will briefly report the detailed in vivo imaging evaluation results using the developed two-dimensional system.

Speaker: Minori Oshima (Kanazawa University)

additional material.pdf

36 Analysis of unstable leakage current in ATLAS18 Strip Sensors after long-term tests

With the upgrade of the LHC to the High-Luminosity LHC (HL-LHC), the Inner Detector will be replaced with the new all-silicon ATLAS Inner Tracker (ITk) to maintain tracking performance in a high-occupancy environment and to cope with the increase in the integrated radiation dose.

Comprising an active area of 165m$^2$, the outer four layers in the barrel and six disks in the endcap region will host strip modules, built with single-sided micro-strip sensors and glued-on hybrids carrying the front-end electronics necessary for readout. Before being shipped out for module building, a total of 24010 ATLAS18 n$^+$-in-p strip sensors, of which 17888 sensors are to be installed in the experiment, were tested at different institutes in the collaboration for mechanical and electrical compliance with technical specifications, the quality control (QC), while technological parameters were verified on test structures from the same wafers before and after irradiation, the quality assurance (QA).

Reverse bias leakage current characteristics of every single sensor and leakage current stability measurements on a sample basis are an important part of QC procedure. During these measurements, a recurring pattern of performance degradation and recovery in leakage current and sensor breakdown after long-term testing has been observed for a subset of sensors. A comprehensive analysis of those changes observed during Sensor QC will be shown. Mitigation and recovery procedures, such as ionizing guns, exposure to UV light and sensor baking, developed by the sensor community and applied at different QC sites will also be highlighted, including their impact on sensor performance.

Speaker: Christoph Klein (Carleton University)

37 Simulation of the Electrical Performance of the ITk ATLAS18 Test Diode and Strip Main Sensors Before and After Irradiation

The ATLAS experiment will be replacing the current inner detector with the Inner Tracker (ITk) to accommodate the increased occupancy and radiation levels anticipated at the High-Luminosity LHC (HL-LHC). The ITk system consists of silicon-based pixel and strip sub-detectors. The strip detectors, fabricated by Hamamatsu Photonics, are based on an n⁺-in-p design with a 75 μm strip pitch and a 300 μm active thickness, and are expected to operate up to a fluence of 1.6x10¹⁵ 1-MeV neq/cm².

To better understand the fundamental behavior of the strip sensors and to guide their operation, we have developed a 2D Sentaurus TCAD model, tuned using optical and electrical characterization data from the test diodes fabricated on the same wafer as well as the main strip sensors. The simulation incorporates material defect models material defects measured from deep-level transient spectroscopy (DLTS), along with a dedicated interface model for the oxide layer in the peripheral region to improve agreement with laboratory measurements. By extending this model to the ITk main strip sensors, the simulations show good agreement with the extensive Quality Control data collected during sensor reception acceptance measurements. Finally, using this updated TCAD model as a starting point, we simulate device performance at the expected HL-LHC fluence and develop new irradiation models based on DLTS data and electrical measurements from irradiated test diodes.

Speaker: Yuzhan Zhao (Carleton University)

38 Design and development of MAPS-based CEPC Inner Tracker

The Circular Electron Positron Collider (CEPC) is next-generation electron positron collider for precision studies of Higgs, flavour physics and beyond. A key component of its tracking system is the Inner TracKer (ITK) using High-Voltage CMOS sensor technology. We will introduce the design of the CEPC ITK, which consists of three barrel layers and four pairs of endcap disks, covering a total active area of 20 $m^2$. HVCMOS sensor using advanced 55nm process is chosen in order to achieve a few micrometer spatial resolution, a few nanosecond timing resolution, with a moderate power consumption. The design of modules is shared for barrel and endcap part to facilitate production. The whole system is designed for minimal material budget, with ~0.7%X0 per layer in the barrel part. The design has been implemented in CEPC software framework for performance study and future optimization.

Speaker: Xiaojie Jiang

39 Investigation of the current-generation mechanisms in the edge region of planar silicon sensors using TCAD and TCT

Radiation-hard silicon sensors used in high-energy physics experiments require a high electric field and are susceptible to surface breakdown at the edges of the planar sensors, especially at the tips of metal contacts or implants, where field peaks develop. These high-field regions, which are influenced by defects at the oxide interface and the geometry of the sensor, can give rise to avalanche breakdown. In addition, generation current can originate from interface states that contribute to surface current, as well as from regions with structural damage in the silicon crystal lattice at the dicing edge.

To investigate the contributions of these current-generation mechanisms and optimize the sensor performance, the edge region of an n$^+$-p-p$^+$ diode including the dicing edge was implemented in Synopsys TCAD to simulate its electrical behavior from 273 K to 333 K. IV and CV tests were simulated and compared to measurements, the influence of key factors—such as surface and edge defect concentrations—was assessed. Transient Current Technique (TCT) simulations were performed in TCAD together with Allpix Squared and compared to measurements. This allowed assessment of the distribution of the electric field and fidelity of its simulation. The results provide a qualitative picture of how and where specific defect types contribute to the leakage current and breakdown at the sensor edge, indicating venues for future studies to further improve understanding of the current-generation mechanisms in the edge region of silicon sensors.

Speaker: Peilin Li (Humboldt University of Berlin)

40 Current and low-field carrier mobility in silicon sensors irradiated to extreme fluences

We present a study of the forward and reverse current in silicon pad diodes irradiated to extreme neutron fluences of up to $5 \times 10^{17}\,n_{eq}/$cm$^2$, corresponding to expected fluences at the innermost radii of tracking detectors at a future circular hadron collider.

At such fluences, the low-doped silicon bulk and the highly doped implant no longer behave like a typical pn diode. Excess free carriers get trapped at radiation-induced deep defects, compensating ionized shallow defects like residual doping in the bulk. Consequently, the carrier concentrations in the bulk decrease and become similar to those in intrinsic silicon, increasing the resistivity of the bulk. At the same time, the radiation-induced defects lead to narrow space charge regions (SCR) with high space charge concentrations and, due to the short lifetimes, the resistivity of the SCR may be less than the bulk resistivity. Hence, the bulk resistivity dominates the current-voltage characteristic for lower forward and reverse bias voltages and the electric field extends into the entire bulk. The bulk resistivity depends on the carrier concentrations and the carrier mobilities, which enables us to determine the decrease to the low-field carrier mobilities due to ionized impurity scattering as a function of the fluence.

The current-voltage characteristics were measured for fluences of $2.3 \times 10^{17}\,n_{eq}/$cm$^2$ and $5 \times 10^{17}\,n_{eq}/$cm$^2$ at different temperatures and are combined with previous measurements of proton-irradiated sensors to extend the fluence range down to $9 \times 10^{15}\,n_{eq}/$cm$^2$.

These results are relevant for modeling signal formation in silicon sensors at potential future hadron colliders and in other harsh radiation environments, and for understanding conditions under which silicon can still be used as a particle detector.

Speaker: Christian Scharf (Humboldt University of Berlin)

41 Proton irradiation for quality assurance of ATLAS18 strip sensors with Birmingham MC40 cyclotron

Proton Irradiation for quality assurance of ATLAS18 strip sensors with
Birmingham MC40 cyclotron

Thomas Thory-Rao, Andrew Stephen Chisholm
on behalf of the ATLAS ITk Strip Sensor Collaboration

The Birmingham MC40 Cyclotron is used to perform proton irradiations of
silicon detector devices as part of the ongoing ATLAS ITk Strip Quality
Assurance program. It provides a dedicated beamline delivering 27 MeV
protons at currents up to a few μA, collimated to a square beam profile
of 10 mm x 10 mm of roughly uniform intensity. Samples are placed within
a thermally controlled box, held below -20C, which is scanned across the
beam allowing a uniform fluence to be delivered without uncontrolled
annealing occurring during the irradiation.

Recently, upgrades have been performed to the sample scanning system,
including new motor stages and improved control software. These upgrades
have increased the maximum scanning speed of the system, allowing the
beam current to be increased from 200nA to 500nA, with the scanning
speed increased proportionately from 4mm/s to 10mm/s. This increase in
turn leads to faster irradiation times; for 6 10mm x 10mm mini sensors
the ITk Strip QA fluence of $1.6 * 10^{15}$ neq/cm$^2$ is now achievable in
under 1.5 hours, twice as fast as before.

A brief history of the facility will be presented, discussing the
facility's early issues of unexpectedly low collected charge for
irradiated mini sensors, and how these were resolved through changes to
the beam collimators and scanning patterns. Following this the current
status of the facility post-upgrade will be outlined in detail, and
measurements of irradiated ITk strip test structures, showing
consistency with both the pre-upgrade system and other irradiation
facilities, will be presented. In summary, this talk will highlight the
Birmingham MC40 Cyclotron's role in the successful continuation of the
ATLAS ITk Strip QA program, along with it's potential use for high
fluence irradiations for future detector R&D.

Speaker: Thomas Thory-Rao (University of Birmingham (GB))

42 Impact of X-Ray Irradiation on CMOS Sensor Performance

Next-generation collider experiments will require pixel detectors that can sustain high radiation doses and operate effectively at extreme luminosities. A CMOS depleted monolithic active pixel sensor has been developed with an advanced readout architecture to meet these demands, offering excellent radiation hardness, high-rate capability, fine spatial resolution, and precise timing performance. Before integration into an actual detector system, the sensor must be thoroughly characterized to ensure optimal operation. This work presents studies performed on the sensor following irradiation with an intense X-ray source to assess its performance under such conditions. The latest measurement results will be discussed.

Speaker: Prof. Prafulla Behera (IIT Madras)

43 Aliasing artifact suppression using artifact map subtraction in single-grating X-ray dark-field imaging

This study presents a novel method to suppress wrapround artifacts in single grating X-ray dark-field imaging (SG-XDFI). SG-XDFI is an emerging technology that can be used to detect small-angle X-ray scattering signals from sample inhomogeneities at the microscale and nanoscale using the spatial harmonic imaging technique. However, when a sample has strong high-frequency components and/or the grating frequency is low, the dark-field image is distorted by spectral overlap-induced aliasing artifacts. Therefore, aliasing artifacts should be suppressed to ensure high-quality dark-field images. In the proposed method, aliasing artifacts are suppressed by generating an artifact map and subsequently subtracting it from the original (i.e., artifact-contaminated) dark-field image, yielding an artifact-free dark-field image. To verify the efficacy of the proposed method, we performed an experiment on a printed circuit board and investigated the image quality. According to our preliminary results, the proposed method effectively suppressed the wraparound artifacts in SG-XDFI, significantly enhancing the image quality.

Speaker: Jonghyeok Lee

Hiroshima(figure,Jonghyeok Lee).pdf

44 Timing resolution of thin planar pixel sensors coupled to TDCpix ASIC measured with Timepix4 beam telescope

The work presents a study aimed for the measuring of timing performance of thin planar pixel sensors (100 and 50 um) using the high resolution TimePix4 beam telescope for precise track-referenced measurements. The sensors were coupled to the triggerless TDCpix ASIC with 100 ps timestamping, originally developed for the GigaTracker of the NA62 experiment at CERN for use with 200 um-thick sensors. The devices were investigated at the CERN Super Proton Synchrotron beamline where the Timepix4 telescope provided particle tracks with a spatial resolution of about 2 um and timing resolution of about 90 ps.
Hardware-level integration of the hybrids with the telescope enabled timing synchronization between the telescope and TDCpix, allowing for precision pixel-level timing studies. For thin sensors, experimental runs were conducted with the device rotated relative to the beam trajectory effectively enhancing the deposited charge and enabling direct comparison with the 200 um-thick reference sensor.
The results show the dependencies of mean matrix timing resolution on sensor bias voltage, discriminator threshold, and incident angle for different sensor thicknesses. They demonstrate improved timing resolution in thinner detectors. Integration of data obtained from hybrids with the telescope tracks enabled the production of intra- and inter-pixel timing resolution maps. These maps reveal spatial non-uniformities in timing performance, correlated with the weighting field distribution, electrode geometry, and charge-sharing effects between pixels.

Speaker: Artem Shepelev (University of Birmingham)

ALL Poster: #101-128

Poster

45 Activation and Sensitivity Study of a Broadband X-ray Gamma-ray Detector INSPIRE for Small Satellite GRAPHIUM

Author: Kazuki Yamamoto
Co-author: Shojun Ogasawara, Joshi Aryaa Rajendra, Soichiro Kojimaa, Kosuke Sato, Kazuo Tanaka, Jun Kataoka, Yoichi Yatsu, Toshihiro Chujo, Hiroki Nakanishi, Makoto Arimoto, Satoshi Hatori, Kyo Kume, Satoshi Mizushima, Shinko Sando, Takashi Hasegawa

Observations in the MeV gamma-ray band are known to be extremely challenging because gamma rays in this energy range cannot be focused with conventional optics and background radiation such as the cosmic X-ray background (CXB) and albedo gamma-ray dominates over source signals. Therefore, observations in this energy range have stagnated for nearly 30 years since the Compton Gamma Ray Observatory (CGRO) conducted measurements in the 1990s. In this context, Waseda University and Science Tokyo are developing a small satellite called GRAPHIUM, which is scheduled for launch in 2027. The onboard X-ray and gamma-ray camera, INSPIRE, is a hybrid Compton camera that adopts GAGG and BGO scintillators. GAGG has excellent characteristics, such as high light output and non-hygroscopicity; however, because GAGG is developed recently, its performance has not yet been sufficiently demonstrated in satellite missions.
In this study, GAGG was irradiated for two hours with protons corresponding to ten years of orbital exposure at the Wakasa Wan Energy Research Center. Gamma-ray spectra were then measured over a period of three months using a high-purity germanium detector. Based on the results, we investigated the activation characteristics of GAGG and estimated the extent to which activation-induced background affects the sensitivity of INSPIRE.

Speaker: Kazuki Yamamoto (Waseda University)

HSTD_abstract_KazukiYamamoto.pdf

46 A compact silicon strip detector design with SoC-FPGA-based readout electronics

Silicon strip detector (SSD) system is wildly used in many collider experiments and cosmic-ray experiments to measure high energy particle trajectory information. Suck system could reach O(10) um tracking resolution and ability to do particle identification for heavy ions. In addition, SSD based beam monitors/telescopes are useful tools for test beam studies to support the R&D of other detectors.
Based on Xilinx Zynq SoC-FPGA, we designed a compact readout electronics system for SSD sensor. This system includes a front-end board with several active components, like IDE1140, ADC, DC-DC, connect to the SSD sensors. The signal on the SSD sensor will be amplified and converted to digital on front-end board. The back-end data-acquisition system (DAQ) is implemented on an Zynq SoC board, which includes both firmware and software for online data processing and monitoring. In this poster, we will introduce this compact SSD readout design, beam monitor application, and test beam performance we achieved.

Speaker: MENGKE CAI (Institute of High Energy Physics, China)

compact_SSD_Design.docx

47 Photon-counting detector projection generation using deep learning for high-selectivity breast microcalcification differentiation

The detection of microcalcifications within breast tissue, composed of fibroglandular and adipose components, is a key indicator in the diagnosis of breast cancer. Differentiating between type 1 (calcium oxalate, CaOx) and type 2 (hydroxyapatite, HA) microcalcifications is clinically important, as they are associated with benign and malignant lesions, respectively. Conventional energy-integrating detector (EID)-based mammography lacks the spectral capability for material decomposition. Photon-counting detectors (PCDs) provide energy-resolved imaging for material decomposition, but their high cost and limited availability restrict clinical use. We propose a method that uses a modified U-Net to generate PCD-like spectral projections from EID data for material decomposition. Reference PCD data were generated via CdTe-based PCD simulation using the Photon Counting Toolkit (PcTk), configured to replicate realistic detector response and energy binning. The generated spectral projections were decomposed into CaOx, HA, and soft tissue maps. Preliminary results showed effective separation of soft tissue and microcalcifications with high selectivity. Quantitative results and further discussion will be provided in the full paper.

Speaker: Soohyun Lee

2025_HSTD_SHL_fig.pdf

48 Readout System for Cosmic X-ray Polarization Detector with Large-scale Pixel Array

This paper presents the design and implementation of the electronic readout system for the CubeSat-based Cosmic X-ray Polarization Detector (CXPD-02), serving as the second-generation prototype verification of the Low Energy X-ray Polarization (LPD) for the Polar-2 experiment. CXPD-02 incorporates the Topmetal-L pixel sensor chip specifically designed for the LPD, featuring the pixel array of the 356 × 512 elements, which represents a 36-fold increase in the number of pixel units compared to the pixel chip used in the previous generation CXPD-01. Thus, the readout design of the system is the critical factor affecting the performance of the detector. To address the challenges posed by large-scale array readout, the system's readout logic is implemented through the digital ASIC on-chip readout of the pixel chip and FPGA algorithms to achieve the Region of Interest Readout Integrated Circuit (ROIRC). The ROIRC employs a sentinel-based detection mechanism to rapidly identify and read out only particle struck pixel regions. This readout process integrates the algorithms: scanning frequency switching, erosion compression, and dynamic background updating, while synchronizing temporally with the signal acquisition from the Gas Microchannel Plate (GMCP). Experimental validation demonstrates that this readout system design significantly enhances overall detector performance, achieving the residual modulation factor of 13.67, exceeding 90% coincidence rate with GMCP events, and 95% data compression efficiency. The detection method of the ROIRC enables the detector to achieve X-ray detection in the low-energy range of 2 to 10 keV.

Speaker: Shi Qiang Zhou

CXPD-02.pdf

49 Design and testbeam study of AMS-02 Layer-0 silicon strip detector ladders

The Alpha Magnetic Spectrometer(AMS-02) is a particle detector that operates on the International Space Station(ISS), which aims to search for antimatter, and dark matter while performing precision measurements of cosmic rays composition and flux. To enhance the detection acceptance by a factor of three, a new large-area silicon tracker layer (Layer-0) will be installed on top of AMS-02 in 2026. Layer-0 is composed of two back-to-back detector layers, each with an active area about $3.5\,\mathrm{m}^2$. To achieve such a large active area with limited power consumption, we designed very long silicon detector ladders. Each ladder has 8, 10, or 12 silicon strip detector sensors (SSDs) connected in serial, producing an effective strip length from 64 cm to 96 cm. To evaluate the performance of these ladders, multiple beam tests were conducted at CERN’s Super Proton Synchrotron (SPS) and Proton Synchrotron (PS) facilities.

In this talk, we present a detailed characterization of ladder performance, including: (i) comparisons across ladders of different lengths; (ii) position-dependence of SSDs along a single ladder; and (iii) the dependence of performance on the incidence angle. Performance is quantified in terms of detection efficiency, charge-collection efficiency, and spatial resolution for minimum-ionizing particles (MIPs).

Speaker: Dexing Miao

50 Charge Response Simulation of Liquid Argon Compton Cameras for Precise MeV Gamma-Ray Event Reconstruction

The Gamma-Ray and AntiMatter Survey (GRAMS) is a balloon-borne and satellite-based experiment designed for MeV gamma-ray observations and indirect searches for dark matter via antimatter detection. It uses a cost-effective and scalable Liquid Argon Time Projection Chamber (LArTPC), offering enhanced sensitivity to MeV gamma rays.
In this energy range, Compton scattering is the dominant interaction in argon, so the detector operates as a Compton camera. We are developing a small-scale prototype, NanoGRAMS, to demonstrate this concept. Precise measurement of deposited energy in argon is critical for accurate event reconstruction. Factors such as argon purity, electron-ion recombination, and the electron drift length in argon are known to influence charge pulse height, affecting both energy deposition measurement and event reconstruction. A realistic NanoGRAMS-based simulation that incorporates these effects is therefore essential.
To model these effects, we employed SolidStateDetectors.jl, a simulation framework originally developed for semiconductor detectors. This tool simulates charge induction on the anode from drifting electrons and purity effects. We extended it with a custom model of electron-ion recombination based on Birks formalism and the charge readout response. Combined with ComptonSoft, which is based on Geant4 and serves as the event reconstruction framework, we investigated their impact on the accuracy of event reconstruction.
In this presentation, we will describe our simulation methodology and results, including the influence of charge drift effects on the event reconstruction, and comparisons between different detector configurations (such as purity, bias voltage, pixel/strip size and the use of Frisch grid) to optimize the performance.

Speaker: Shota Arai (The University of Tokyo)

51 Development of a MAPS-based Silicon Pixel Beam Telescope

To advance particle detector research, a MAPS-based silicon pixel beam telescope has been developed, which will be used in the High-Energy Proton Beam Experimental Station (HPES). As part of the CSNS-Ⅱ upgrade project, HPES will provide a single-particle proton beam with adjustable energy ranging from 0.8 to 1.6 GeV. As the core detector system of HPES, the telescope comprises six ultra-thin telescope modules, each consisting of a Monolithic Active Pixel Sensor (MAPS), an auxiliary PCB board and an aluminum shield box with a cooling system. The material budget per module is about 0.061%X0, equivalent to 50 μm silicon and two layers of shield film with a thickness of 12.5 μm. Simulations indicate that the beam telescope can achieve a telescope resolution better than 2 μm using a 1.6 GeV proton beam. Additionally, an electronics system has been developed for the telescope, with each module equipped with a readout board for individual control. To accommodate DUTs with various sizes, a dedicated high-precision experimental station is available for the users, featuring two telescope arms for mounting the six telescope modules and a six-axis motion stage for the DUTs in the center. The system also includes a trigger detector and a trigger logic unit to provide proton-level trigger signals for both the telescope and the DUT. To validate the design, a prototype with six modules was tested using a 1.3 GeV electron beam. The results demonstrated a spatial resolution of 5.7 μm for the DUT and 2.7 μm for the telescope, with a detection efficiency exceeding 99.5%. Since the beam tests were performed with an electron beam at an energy lower than 1.6 GeV, the effect of multiple Coulomb scattering was more significant, resulting in a slightly worse telescope resolution compared to the simulation.

Speaker: Lankun Li (IHEP)

52 Prototype assembly and tests for CEPC vertex detector

The first four layers of the CEPC(Circular Electron Positron Collider) vertex detector are designed using wafer-scale sensors based on stitching technology. To ensure the inner most layer is as close as possible to the central beam pipe, the design radius is set at 11 mm, posing significant challenges for the development of bent detector modules. Currently, a prototype model with a minimum bending radius of 11 mm has been successfully fabricated using 30 µm-thick dummy wafers. A full four-layer model of the CEPC vertex detector will be developed in the following studies, including flexible cables, support structures, and bent chip bonding techniques. Additionally, to verify the feasibility of silicon pixel sensors after bending, a small-area bent detector module with a radius of 20 mm was fabricated using 50 µm-thick MAPS(Monolithic Active Pixel Sensors) chips. The beam test with a 1.3GeV electron beam confirmed that the sensor bent to a radius of 20 mm exhibits the same performance as before bending. Further tests with smaller bending radii are planned. These results will provide valuable experience for the subsequent development of the CEPC vertex detector.

Speaker: Liangchenglong Jin

53 SIPAC A SiPM readout ASIC for the CEPC Detector

The Circular Electron Positron Collider (CEPC) is proposed for Higgs boson research, and will includes several detectors, such as the Electromagnetic Calorimeter (ECAL), Hadronic Calorimeter (HCAL), and Muon detector. Silicon photomultiplier (SiPM) is widely used in these detectors for light conversion. This paper presents a prototype design of SIPAC (SiPM readout ASIC for calorimeter).
Table 1 outlines the readout requirements of the ECAL and HCAL. Given the limitations of existing commercial chips and the CEPC detector’s requirement for a large-scale deployment of SiPM and their associated readout circuits, a dedicated SIPAC readout chip has been developed. With a maximum input charge of 3.84 nC, employing a CSA as the front-end amplifier would necessitate an impractically large input capacitor. To realize SiPM voltage adjustment, AC coupling is implemented between the preamplifier and the SiPM. Furthermore, given the slow response of the SiPM signal after passing through the crystal, SIPAC utilizes voltage amplifier as the front-end solution. Given the critical impact of the noise on time and energy resolution, the design of the shaper is critical. The energy path employs a slow shaper with two stages of low-pass filters, achieving an SNR of 8, while the timing path uses a fast shaper with a Bandpass filter, achieving an SNR of 12. Signals after shaping are sampled or compared, then quantized by the ADC or TDC and read out by the digital module. The four channels’ switched capacitor sampled signals are processed by a shared ADC and serializer for conversion and output, with each channel featuring a dedicated TDC. Figure 1 shows the overall architecture.
To address the gain variations between different SiPMs, an on-chip DAC is integrated into each channel for precise gain calibration of each SiPM. AC coupling is implemented for signal transmission, effectively isolating the adjustment effects of the DAC from the readout circuit. The signal after shaper is sampled by a switched-capacitor circuit and digitized by the SAR ADC for energy measurement. As shown in Figure 2, the post-simulation results indicate that within the input dynamic range of 1.28 pC to 3.84 nC, the nonlinearity errors are 0.4% for the high-gain path and 0.3% for the low-gain path. Furthermore, the SAR ADC achieves an ENOB of 10 bits.
For the time measurement path, the TDC employs a hybrid measurement structure combining coarse counting and fine counting. The coarse counting is derived from a counter, while the fine counting is determined by a delay line. The TDC is designed to measure the time of arrival (TOA). The digital codes generated by the TDC and ADC are encoded and serialized by the digital module for data transmission.
In summary, SIPAC, a dedicated SiPM readout ASIC for the CEPC detector, features a wide dynamic range (1.28 pC to 3.84 nC), supports a 500 kHz event rate, and achieves a 200 ps time resolution at 1.28 pC. The integrated TDC delivers 100 ps resolution with INL and DNL below 1 LSB, while the ADC achieves a 10-bit ENOB.
Currently, the chip is undergoing functional testing. The front-end circuit and TDC are working normally, and the ADC is under testing. It is expected that the accuracy of the TDC will reach 100ps, and the dynamic range of the front-end meets the design requirements. Detailed performance tests will be conducted after the functional tests are completed.

Speaker: YunQI Deng (Institute of High Energy Physics)

54 A 5~36 ps Event-Driven Vernier Time-to-Digital Converter in 55-nm CMOS

High resolution time-to-digital converter (TDC) is widely used in high-energy physics experiments, TOF-PET, and other fields. Targeting next-generation photon detectors (MCP-PMT, SiPM), this work presents a TDC prototype design achieving state-of-the-art time resolution in a 55-nm CMOS process.

The design integrates two timing cores for independent time-of-arrival (TOA) and time over threshold (TOT) measurements. Each core has four primary components: two ring oscillators (VRO) based on a vernier structure, a controller, a quantization block and counters. The VRO includes a slow ring (X-chain) and a fast ring (Y-chain), both employing 15 delay units. Each delay unit adopts a voltage-controlled starved-current-mirror NAND gate. The time resolution is determined by the difference between the unit delays of the X chain and Y chain.

The TDC employs event-driven logic to reduce power consumption. Upon event detection, the controller segments the pulse into START and STOP signals to enable both VRO rings. The SR-latch array in the quantization block synchronously captures phases states across all NAND outputs, comparing each rising and falling edges. Measurement terminates when X-chain and Y-chain phase align, latching the corresponding 30-bit thermometer code. The VRO enters low-power standby mode after quantization until reactivated by subsequent events. A 10-bit coarse counter and a 10-bit fine counter provide a dynamic range of 2.4 μs. Finally, the two cores generate 100-bit raw data, which is serialized and transmitted through a serializer working at 640 MHz.

The post-layout simulations demonstrate a fitting resolution of 1.77 ps under typical condition. The differential nonlinearity (DNL) and integral nonlinearity (INL) is within ±1 LSB and ±2 LSB, respectively. The TDC consumes 8 mW during active operation and 0.72 mW in standby mode after event completion. Preliminary tests confirm correct operation of the VRO rings with achievable time resolution ranging from 5 ps to 36 ps. Additional testing is currently underway, with results to be reported subsequently.

Speakers: Hui Jiang (IHEP), Xiongbo Yan (IHEP)

55 A large dynamic range front-end readout circuit based on first-order Delta-Sigma modulation for Calorimeters

Calorimeters play a vital role in particle acceleration experiments. Their readout systems are confronted with the dual challenges of unpredictable particle responses and nanosecond-scale signal fluctuations. Attaining a resolution below 5%, a dynamic range of 60 dB with low power consumption continues to pose significant technical challenges. This study is grounded in the architecture of first-order Delta-Sigma Modulation (DSM), including an integrator, a comparator, a latch and a Time to Digital Convertor (TDC), realizing real-time readout of charge signals with a dynamic range of 160 fC-160 pC. To enhance the time/energy resolution and low power, a two-step TDC has been developed to achieve a better compromise between resolution and dynamic range. It comprises a counter-type TDC and a delay chain TDC as coarse and fine counts separately. The dynamic range of the TDC is about 640 ns with a LSB of 70 ps, and a measurement error of less than 1.3 LSB, with an rms value of about 3 ps. The preliminary test results show that the total energy nonlinear error is less than 3.81% which is encouraging. The total power consumption is about 6.12 mW using 180nm CMOS process.

Speaker: Ping Yang (Central China Normal University)

A large dynamic range front-end readout circuit based on first-order Delta-Sigma modulation for Calorimeters_PingYang.pdf

56 Study of LGAD with Shallow and Deep Carbon Implantation

This work investigates the performance of Low Gain Avalanche Detectors (LGADs) developed by the Institute of High Energy Physics (IHEP) with different carbon implantation schemes. To characterize sensor behavior, systematic measurements of capacitance, leakage current, temporal resolution, and charge collection were performed. Radiation hardness was assessed through neutron irradiation up to a fluence of 2.5× 1015neq/cm2. The results demonstrate that both shallow and deep carbon implantation contribute to enhanced radiation hardness, although their impacts on sensor performance are not entirely identical. Nevertheless, increasing the carbon dose in deep implantation configurations results in performance degradation, as evidenced by capacitance and beta source measurements. These findings provide new insights into the optimization of carbon implantation for radiation-hardened LGAD design and contribute to a broader understanding of design strategies for radiation-hardened detectors.

Speaker: Dr Yunyun Fan (IHEP)

Welcome: party

Convener: HSTD14 (AS)

Monday 17 November

Welcome: Opening remark

Convener: HSTD14

0. Detector Concepts, Simulations: Mon-1

57 Operational Experience and Performance with the ATLAS Pixel detector at the Large Hadron Collider at CERN

The tracking performance of the ATLAS detector relies critically on its 4-layer Pixel
Detector, with a sensitive area of ~1.9 m2 and 92 million pixels. Its original part,
consisting in 3 layers of planar pixel sensor is continuously operating since the start
of LHC collisions in 2008, while Its innermost layer, the Insertable B Layer (IBL) at
about 3 cm from the beam line, was installed in 2015 before the start of LHC Run2
and consists of both planar and 3D pixel sensors, with FE-I4 readout frontends at
130nm CMOS technology.
As the closest detector component to the interaction point, this detector is subjected
to a significant amount of radiation over its lifetime. At present, at the start of
2025 Run3 LHC collisions, ATLAS Pixel Detector on innermost layers is operating
after integrating fluence of O(10**15) 1 MeV n_eq cm-2.
In this talk the key status and performance metrics of the ATLAS Pixel Detector are
summarised, putting focus on performance and operating conditions at a over
performing LHC, with special emphasis to radiation damage and mitigation
techniques adopted, with prediction of their evolution until the end of LHC Run3 in
2026.
These results provide useful indications for the optimisation of the operating
conditions for the new generation of pixel trackers under construction for HI-LHC
upgrades.

Speaker: Tobias Bisanz (TU Dortmund)

58 Operational experience and performance of the Silicon Vertex Detector after the first long shutdown of Belle II

In 2024 the Belle II experiment resumed data taking after its Long Shutdown 1, which was required to install a two-layer pixel detector and upgrade components of the accelerator. We describe the challenges of this upgrade and report on the operational experience during the subsequent data taking. With new data, the SVD confirmed high hit efficiency, large signal-to-noise and good cluster-position resolution. SuperKEKB’s instantaneous luminosity is expected to increase significantly, resulting in a larger SVD occupancy caused by beam-related background. Considerable efforts have been made to improve the SVD-reconstruction software by exploiting the excellent SVD hit-time resolution to determine the collision time and reject out-of-time hits caused by the beam-related background. A novel procedure to group SVD hits event-by-event, based on their time, has been developed by using the grouping information during reconstruction, significantly reducing the fake rate, while preserving the tracking efficiency. The front-end chip (APV25) is operated in “multi-peak” mode, reading six samples. During data taking, we tested a 3/6-mixed acquisition mode, based on the timing precision of the trigger, that reduced background occupancy, trigger dead-time and data size. Studies show a moderate radiation-induced increase in sensor current and strip noise. However, such damage will not degrade the performance during the lifespan of the detector.

Speakers: Jim Libby (Indian Institute of Technology Madras), Kieran Amos (INFN Trieste)

59 CMS Tracker Status, Challenges, and Performance in Run 3

The innermost tracking system of the CMS experiment consists of two tracking devices: the Silicon Pixel and Silicon Strip detectors. The tracker was specifically designed to very accurately determine the trajectory of charged particles or tracks, enabling precise reconstruction of primary and secondary vertices, as well as momentum measurements, in the high-luminosity environment of the LHC. Since the start of Run 3 in 2022, the CMS tracker has operated under increasingly demanding conditions, including higher instantaneous luminosities and increased pileup. In this talk, we present the current status and operational experience of the CMS tracker during Run 3, with a focus on its performance under these new conditions. We review key metrics including hit efficiency, alignment precision, tracking efficiency, and vertex resolution. The tracker has continued to perform at or near design specifications, benefitting from targeted improvements in alignment strategies, calibration workflows, and real-time monitoring. We also discuss the main challenges faced during Run 3, such as radiation-induced effects on sensors and electronics. In particular, aging effects due to cumulative radiation damage are becoming increasingly relevant and require careful monitoring and mitigation to ensure sustained performance.

Speakers: CMS Collaboration, Davide Zuolo (University of Colorado - Boulder)

10:20 Coffee

0. Detector Concepts, Simulations: Mon-2

60 Phase-2 Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will replace its existing Inner Detector with the new Inner Tracker (ITk) to cope with the operating conditions of the high-luminosity phase of the LHC (HL-LHC) scheduled to start in 2030. ITk is an all-silicon tracker with a pixel detector core surrounded by a strip detector resulting to an almost 180 m2 total silicon surface. This new tracker is designed to withstand the radiation damage due to hadron fluences of over 2x10^16 neq/cm2 accumulated at the maximum integrated luminosity of 4000 fb-1 to be attained by the end of the HL-LHC operation. It will also allow for efficient charged particle tracking in a very dense collision environment.

After an extensive prototyping phase, ITk is currently in pre-production and will transition into production mode by the end of 2025. In this contribution the design of the ITk detector and its expected performance will be presented. An overview of the current status of the two main pixel and strip detector subsystems as well as the associated common infrastructure, will be provided. Particular emphasis will be given on the preparation for production and its more challenging aspects.

Speaker: Thomas Koffas (Carleton University)

61 The ATLAS High-Granularity Timing Detector for the HL-LHC: project status and results

The HL-LHC will provide instantaneous luminosities up to $7.5 \times 10^{34}~$cm$^{−2}$s$^{-1}$, and the increased interaction rate and particle flux will degrade the ATLAS event reconstruction performance. The endcap and forward region where the liquid Argon calorimeter has coarser granularity and the inner tracker has degraded resolution will be particularly affected. A High-Granularity Timing Detector (HGTD) will be installed in front of the LAr endcap calorimeters for pile-up mitigation and luminosity measurements. The HGTD is a novel detector introduced to augment the new all-silicon Inner Tracker in the pseudorapidity range from 2.4 to 4.0, adding the capability to measure charged-particle trajectories in time as well as space. Two double-sided layers of silicon sensors will provide precision timing information for charged particles with a resolution as good as 30 ps per track to help assign each particle to the correct vertex. Readout cells have a size of 1.3 mm $\times$ 1.3 mm, leading to a highly granular detector with ~3.7 million channels. Low-Gain Avalanche Detectors (LGAD) technology has been chosen as it provides enough gain to reach the large signal over noise ratio needed. The requirements and overall specifications of the HGTD will be presented as well as the technical design and the project status. The R&D efforts on the sensors, the readout ASIC, and the other components, supported by laboratory and test beam results, will also be presented.

Speaker: Helena Santos (Laboratory of Instrumentation and Experimental Particle Physics)

62 The CMS Tracker Upgrade for Phase-2: Meeting the Challenges of the HL-LHC

The High-Luminosity Large Hadron Collider (HL-LHC) will significantly increase the instantaneous luminosity of proton-proton collisions, pushing the CMS experiment into a regime of extreme radiation levels, high particle multiplicities, and unprecedented data rates. To maintain and extend the physics performance of the CMS detector under these conditions, a complete replacement of the tracking system is underway as part of the Phase-2 Upgrade. This talk presents the design, goals, and status of the Phase-2 CMS Tracker Upgrade, which includes entirely new silicon pixel and strip detectors with enhanced radiation hardness, finer granularity, and extended pseudorapidity coverage. The upgraded tracker will also feature on-detector data reduction through the use of real-time trigger information—an essential capability for sustaining low trigger thresholds at the HL-LHC. Special emphasis is placed on innovations in sensor technology, powering and cooling strategies, and the mechanical integration of large-scale modular components. We discuss the R&D, prototyping, and production progress, along with results from recent beam tests and system integration campaigns. The talk will also highlight key challenges in quality assurance, large-scale assembly, and pre-installation testing, as well as the timeline toward installation and commissioning during Long Shutdown 3.

Speakers: Amrutha Samalan (Paul Scherrer Institute (CH)), CMS Collaboration

63 Vertex detector development for future lepton collider

The vertex detector is a critical component of the future lepton collider, such as Circular Electron Positron Collider (CEPC). It is designed to achieve extremely high spatial resolution (3–5 micrometers) for precisely tracking the decay vertices of particles, particularly in studies related to the Higgs boson.

Significant progress has been made in the development for silicon vertex detector in China. A beam telescope device composed of six Taichu3 chips was successfully tested at DESY in December 2022, confirming that the single-point spatial resolution of the Taichu3 pixel sensor chip is better than 5 micrometers, with a detector efficiency above 99%. A vertex detector prototype featuring six double-sided ladders with 24 Taichu3 chips completed beam testing at DESY, further validating its performance.

This talk will also cover the R&D plan for the future, including prototyping a vertex detector based on stitching technology.

Speaker: Zhijun Liang

12:10 Lunch Mon

0. Detector Concepts, Simulations: Mon-3

64 ALICE 3 Silicon Tracker: Design, Status and Prospects

ALICE 3, a next-generation heavy-ion experiment at the LHC, is proposed as part of the Phase IIb upgrades during the fourth long shutdown (LS4), scheduled in 2034-2035, with data taking planned from Run 5. ALICE 3 aims to exploit the full potential of the High-Luminosity LHC as a heavy-ion collider, targeting an integrated luminosity of 35 nb$^{-1}$ in Pb$-$Pb and 18 fb$^{-1}$ in pp collisions. The physics programme will emphasise heavy-flavour dynamics, electromagnetic probes, and precision low-momentum measurements to probe QCD matter across collision systems.

Central to this effort is the silicon vertex and tracking detector, designed to provide a pointing resolution of 10 ${\mu}$m at $p_\textrm{T}$ = 200 MeV/c at midrapidity and to cover a pseudorapidity range of $|\eta| \leq$ 4. It consists of an Inner Tracker and an Outer Tracker, comprising 11 barrel layers (0.5 $\leq r \leq$ 80 cm) and 2 x 12 disks ($|z| \leq$ 350 cm), covering a total area of about 60 m$^2$. Both sub-systems comprise sensors based on CMOS MAPS technology, building on advances made in the ALICE ITS2 (Run 3) and ITS3 upgrade (Run 4). The Inner Tracker is subdivided into the Vertex Detector and the Middle Layers, featuring MAPS with intrinsic position resolution of 2.5 ${\mu}$m and 10 ${\mu}$m, respectively. The Vertex Detector, located inside the beam pipe, comprises three layers with a material budget as low as 0.1$\% X_0$ per layer. Its retractable design allows the innermost layer to be positioned at 0.5 cm from the beam axis, where the sensors are exposed to radiation levels of 1$\times$10$^{16}$ (1 MeV) n$_{eq}$/cm$^2$ and 300 Mrad, as well as hit rates of 100 MHz/cm$^2$. The Middle Layers, surrounding the Vertex Detector outside the beam pipe, consist of four barrel layers and three disks on either side. The Outer Tracker, comprising four barrel layers and six disks on either side, targets a material budget of 1$\% X_0$ per layer and is designed for large-area coverage with modular, industrially scalable production.

This contribution will discuss the core design concepts and highlight key R&D efforts in sensor development, mechanics, integration, and modularisation, toward the Technical Design Reports expected in 2026.

Reference: ALICE Collaboration, "Letter of intent for ALICE 3: A next-generation heavy-ion experiment at the LHC", CERN-LHCC-2022-009, LHCC-I-038, arXiv:2211.02491 [physics.ins-det].

Speaker: Kshitij Agarwal (Universita e INFN Trieste (IT))

65 MAPS-based LHCb Upstream Pixel Tracker: challenges and development

The LHCb experiment is planning a major upgrade (Upgrade II) during the LHC Long-Shutdown 4 to fully exploit the flavour physics potential of the High Luminosity LHC. The Upstream Tracker (UT), a silicon strip subdetector and key component of the current LHCb tracking system, will have to be upgraded to tackle the higher event rate and harsher radiation environment. A MAPS-based pixel UT has been proposed since the Upgrade II Framework TDR, and various scoping scenarios have been studied after implementing the detector concept in simulation. We will report key conclusions from the simulation study, including the UT-related tracking performance with different designs. Based on the simulation the key specifications for sensor chip are derived, including good spatial resolution, nanosecond-level timing for bunch tagging, radiation hardness up to $3 \times 10^{15} n_{eq} cm^{-2}$, just to name a few most challenging ones. The sensor options will be discussed, including common development with Mighty Tracker, and dedicated HVCMOS sensors in smaller feature size of 55nm process which is expected to be radiation hard. The optimization of the module and stave for minimal dead area and material budget are ongoing; prototyping has been starte. Plans for development towards the TDR and beyond will also be briefly mentioned.

Speaker: Yiming Li (IHEP, CAS)

66 The LHCb Mighty-Pixel Upgrade: HV-MAPS Silicon Tracking for the HL-LHC

Presenting on behalf of the Mighty-Tracker collabration of the LHCb experiement

Abstract

The LHCb experiment at CERN’s Large Hadron Collider is a forward spectrometer optimised for precision studies of heavy-flavour physics, with a particular focus on CP violation and rare decays of beauty (b) and charm (c) hadrons. To fully exploit the High-Luminosity LHC (HL-LHC), where LHCb will operate at a nominal luminosity of 1×1034 cm⁻² s⁻¹, the detector will undergo a major upgrade during Long Shutdown 4 (2034–35). This upgrade will enable the collection of up to 300 fb⁻¹ of data, providing unprecedented sensitivity to physics beyond the Standard Model.
Operating under HL-LHC conditions presents significant challenges, particularly high occupancies and intense radiation levels in the inner tracking regions near the beam pipe. To address these, the central section of the current Scintillating Fibre (SciFi) tracker will be replaced by Mighty-Pixel, a next-generation silicon tracker with high granularity and radiation hardness. It is based on High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) produced using commercial CMOS technology. Covering an active area of ~8 m² across six layers, Mighty-Pixel is designed to provide the robust tracking performance required in the HL-LHC environment, offering excellent spatial resolution, fast timing, and a low material budget.
This talk will present the current R&D status of Mighty-Pixel, now entering its second prototyping phase, and will cover sensor design, readout electronics, mechanics, and cooling, as well as the road map toward pre-production, full-scale construction, and installation.

Speaker: Tianqi Gao (University of Cambridge (GB))

Hiroshima_Abstract_MightyPixel_Tianqi.docx

67 Design and Characterization of a Radiation-Hardened CMOS Image Sensor Prototype

Radiation-tolerant CMOS active pixel sensors (APS) are demanding for imaging and monitoring systems in high-energy physics facilities, nuclear power plants and aerospace applications. However, the Total Ionizing Dose (TID) effects can significantly degrade image quality due to increased dark current and deteriorated transistors characteristics. This work presents a radiation-hardened CMOS image sensor (CIS) prototype developed in a 180 nm CMOS process, featuring a 1280 × 720 pixel-array with a 10 $\mu\text{m}$ pitch. The design integrates a customized photodiode, in-pixel electronics, and column-parallel 10-bit single-slope analog-to-digital converters. The digitized pixel outputs are formatted into frames, serialized and transmitted via the high-speed LVDS interface. Enclosed Layout Transistors (ELT) are implemented to improve the radiation tolerance of the image sensor. Prototype samples have been irradiated up to 100 Mrad ($SiO_2$). Preliminary test results on dark current and optical response, both before and after irradiation, will be reported.

Speaker: Pengxu Li (School of Physics, Zhejiang University)

15:20 Tea

1. Pixel and Strip Sensors: Mon-4

68 Test beam studies of MALTA2, a depleted monolithic active pixel sensor, using 180 GeV hadron beam at CERN SPS

The MALTA2 sensor is the second prototype in the MALTA family of Depleted Monolithic Active Pixel Sensors, developed using a modified 180 nm CMOS imaging process and optimized for operation in the high-radiation and high hit-rate conditions of future collider experiments. With a matrix of 224 × 512 pixels and a 36.4 $\mu$m pitch, MALTA2 is designed for fast charge collection, low noise, and low power operation. This work focuses on evaluating the performance of a MALTA2 variant incorporating very high doping of the $n^{-}$ layer, aimed at improving radiation hardness. Such a MALTA2 sample was irradiated up to a fluence of 5×$10^{15}$ 1 MeV $n_{eq}/cm^{2}$ and characterized in a dedicated test beam campaign at the CERN SPS using a 180 GeV hadron beam. The sensor maintained hit efficiencies above 95% up to 3×$10^{15}$ 1 MeV $n_{eq}/cm^{2}$, with a performance reduction observed at the highest fluence, in line with expectations for radiation-induced damage. Grazing angle measurements were performed to study the charge collection behavior and assess tracking performance across varying beam incidence angles. Cluster size evolution with incident angle provided insight into the depletion behavior after irradiation. The results from the very high doping will guide the development of prototypes featuring ultra-high $n^{-}$ layer doping, aiming to achieve greater radiation hardness in next-generation silicon tracking detectors.

Speaker: Anusree Vijay (Indian Institute of Technology Madras)

HSTD14_summary.pdf

69 Testing and Characterization of Wafer-Scale MAPS Prototypes for the ALICE ITS3 Upgrade

The ALICE experiment will upgrade the innermost three layers of its vertexing detector, the Inner Tracking System (ITS), during the next LHC Long Shutdown (LS3) with a novel, bent, ultra-light MAPS-based tracker. Six wafer-scale sensor chips will be bent into three cylinders, held in place only by carbon foam, leaving no material except for the silicon die in most of the ALICE central barrel acceptance. Two prototype ASICs, approximately $25.8\,\mathrm{cm}$ called MOSS (MOnolithic Stitched Sensor) and MOST (MOnolithic Stitched sensor with Timing), have been produced. These two chips follow complementary approaches to evaluate the use of stitched CMOS sensors for the first time in an HEP experiment.

In particular, MOSS employs a less dense integration, exploring the feasibility of stitched power and signal distribution, as well as front-end qualification. MOST, on the other hand, pushed more towards the density limits, qualifying power domain segmentation using power switches to detach regions with production failures.

This contribution will give an overview of various results from powering tests, functional studies, pixel matrix characterization, and in-beam tests of both test structures. The yield of MOSS is estimated to be approximately $90\%$. This number takes into account powering, as well as functional aspects such as digital and analog pulsing, where a fraction of observed failures is caused by the test chip architecture. Disregarding these failures, the yield of the final ITS3 sensor ASIC will be achieved up to $>98\%$.
Furthermore, it was shown that MOSS can operate with $>99\%$ efficiency and $<10^{-6}\,\mathrm{pixel}^{-1}\,\mathrm{event}^{-1}$ fake-hit rate up to $400\,\mathrm{krad}$ TID and $4\cdot 10^{12}\,1\,\mathrm{MeV}\,\mathrm{n}_\mathrm{eq}\,\mathrm{cm}^{-2}$ NIEL.

This presentation will highlight the most recent results of power testing, functional testing, and matrix characterization of the prototype chips and their implications towards the final ITS3 ASIC design.

Speaker: Nicolas Tiltmann (CERN, Universität Münster (DE))

70 Development of COFFEE3: an HVCMOS pixel sensor prototype in 55 nm process for high-energy particle tracking

High-Voltage CMOS (HVCMOS) pixel sensors are promising candidates for tracking applications in future high-energy physics experiments due to their excellent comprehensive performance in terms of radiation resistance, time resolution, position resolution and power dissipation. Driven by the requirements of Upstream Pixel Tracker in the LHCb Upgrade II and future electron-positron colliders, a series of prototypes named COFFEE are developed in a 55 nm HVCMOS process. While maintaining high spatial resolution and reasonable power consumption, we aim to achieve a few nanosecond time resolution under hit density up to 100 MHz/cm2. Building on the validation of sensing diode and the in-pixel amplification in COFFEE2, COFFEE3 in this work focuses on time measurement and high-density hit readout. Two distinct readout schemes and some test structures have been developed. One scheme only digitizes within the pixel and then parallelly transfers the data to the bottom of the array for time stamping; the other integrates a coarse-fine TDC based within each pixel. The time information is first stored locally in the pixel and then transmitted to the bottom of the array through the column-level data bus in order of priority. Both architectures are expected to achieve a time resolution of within 5ns, but they have different performance focuses in terms of the ability to handle high hit rate or low power consumption. This report will present the design and preliminary test results of COFFEE3, along with its planned future developments.

Speaker: Yang ZHOU (IHEP (Institute of High Energy Physics), CAS)

Welcome: Reception

Convener: HSTD14

Tuesday 18 November

1. Pixel and Strip Sensors: Tue-1

71 LF-MightyPix: A second HV-MAPS prototype for the LHCb Mighty Tracker

After LHC Upgrade II at CERN, LHCb aims to run at an instantaneous luminosity of $1.5 \times 10^{34}/cm^2/s$ and a total integrated luminosity of $300 fb^{-1}$. To support this high-luminosity operation, upgrades are planned for the LHCb detectors, including the downstream tracker, known as the Mighty Tracker. One of the key upgrades is the introduction of silicon pixel detectors, called MightyPix, into the central region of the Mighty Tracker. We have developed prototype chips for MightyPix based on the HV-MAPS (High Voltage Monolithic Active Pixel Sensors) design fabricated using a commercially available CMOS process on high-resistivity wafers. This approach enables the large-scale production of the high hit-rate capable (~ $32 Mhits/cm^2$), radiation hard (NIEL of $3 \times 10^{14}n_{eq}/cm^2$, TID of 40Mrad) pixel detectors required by the Mighty Tracker.

LF-MightyPix has been fabricated as a second prototype chip, using a different foundry than the first and upcoming third prototype chip. This serves to evaluate the feasibility of using an alternative foundry without impacting the overall project. The chip size of LF-MightyPix is $3.3 mm \times 4 mm$ with a pixel pitch of $100 \mu m \times 100\mu m$. For each hit, both the time of arrival and the time over threshold are recorded to ensure correct bunch crossing identification at 40 MHz. In addition to demonstrating foundry compatibility, the chip has implemented digital interfaces and protocols tailored to the LHCb DAQ/Control system, e.g., 1.28Gbps data rate with DC-balanced encoding and “Timing and Fast Control” interface.
In this presentation, we will report on the performance of the LF-MightyPix evaluated both electrically and using particles. We will also outline the development plan of MightyPix, including the next prototype chip.

Speaker: Toko Hirono (KIT)

72 An update on the CMS HGCAL

The CMS Collaboration is getting ready to replace its current endcap calorimeters with a high-granularity calorimeter (HGCAL) to overcome the high radiation effects and the unprecedented event pileup problems in the upcoming High Luminosity LHC (HL-LHC) era. HGCAL featuries a previously unrealized transverse and longitudinal segmentation, for both the electromagnetic and hadronic compartments, with 5D information (space-time-energy) read out. The current design uses silicon sensors for the electromagnetic section and high-irradiation regions of the hadronic section, while in the low-irradiation regions of the hadronic section plastic scintillator tiles equipped with on-tile silicon photomultipliers (SiPMs) are used. The full HGCAL will have approximately 6 million silicon sensor channels and over 200 thousand channels of scintillator tiles. This will facilitate particle-flow-type calorimetry, where the fine structure of showers can be measured and used to enhance particle identification, energy resolution and pileup rejection. In this talk we present the ideas behind the HGCAL, the current status of the project, the evolution of the detector systems with what is learned from the beam tests as well as the design and operation of test systems and the challenges that lie ahead.

Speaker: CMS Collaboration

73 Investigations of the core column issue in ATLAS ITk pixel modules

During the testing of pre-production and production of ATLAS ITk pixel modules the readout of modules can fail. These failures are due to issues in core columns causing the trigger processing inside the ITkPix chip to deadlock. This can be mitigated by disabling one or more core columns within the ITkPix chips. Disabling a core column results in a loss of 2% of the active area of a chip and 0.5% of a module.
A range of studies has been made to determine the characteristics and the origin of the core column issue by mining the ATLAS ITk production database, electrical tests at wafer and module level, and investigations of mechanical damage. No definitive cause has been identified but the evidence indicates that it is due to mechanical damage introduced during the flip-chip process.
This contribution will describe the core column issue and its impact on performance of the detector. The investigations to determine the causes will be described and mitigations discussed.

Speaker: Craig Buttar (University of Glasgow)

74 Quality Assurance during production of the ATLAS18 ITk strip sensors

ATLAS ITk Collaboration

We describe the extensive quality assurance programme undertaken during the production of the ATLAS ITk strip sensors. Quality Assurance (QA) is the systematic process of preventing defects during production, rather than identifying them after the fact. It uses well defined testing procedures to monitor the production process, ensuring consistent process control and minimizing variability. ATLAS QA is done on test structures fabricated at the periphery of the same wafers used to produce the actual sensors, thus ensuring that these structures are a good representation of the sensor quality. The test structures consist of test chips, which include strips, diodes, MOS capacitors, and special structures for monitoring of parameters such as bias resistor values, interstrip resistance, coupling capacitance and flat band voltage. Additionally, miniature sensors with the same design as the main sensor, but with reduced area, allow measurement of the charge generated during irradiation with a beta source.
Test structure semiconductor parameters are measured on both unirradiated samples and samples subjected to irradiation. From every batch, at least one miniature sensor and one diode are irradiated with protons or neutrons to monitor bulk damage, and one test chip and one diode are irradiated with protons or gammas for ionization damage. The test chips are irradiated using gammas and reactor neutrons to the equivalent dose (660 kGy) and fluence $ (1.6 \times 10^{15} neq/cm^2)$ expected in the high luminosity-LHC after 1.5 times its lifetime of 14 years. Miniature sensors are irradiated to the same neutron fluence as the test chips, or the equivalent proton fluence. Monitor diodes are irradiated alternately to the maximum fluence to measure the degradation of the leakage current, and to one third this value to observe the full depletion voltage within the operational range of the measurement setups. Unirradiated test structures are measured on a probe station at room temperature. Irradiated test structures are wire bonded to a PCB to provide connectivity, and measured at -21C and 4% relative humidity.
All the measurements obtained from the tests are uploaded to a database and analysed using python scripts that provide validation, parameter extraction, statistics, trends and parameter correlations.
After four years of sensor production, the QA process has shown reliable performance across multiple test sites. Both tests and irradiations remained fully operational throughout production. A few deviations from the acceptance criteria, such as low flat band voltage, high full depletion voltage, and variations in the magnitude and uniformity of the p-stop doping have been identified and timely reported back to the vendor. However, most of the evaluated parameters have remained between the defined specifications. Out of the total ordered strip sensors, over 80% (572 batches) are tested and accepted as-is. Six batches are rejected, including four due to QA issues related to low p-stop doping.

Speaker: Robert S. Orr (University of Toronto)

10:20 Coffee

1. Pixel and Strip Sensors: Tue-2

75 Evaluation of quality control (QC) of ATLAS18 production ITk strip sensors

To address the demanding operational requirements of the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC), the ATLAS experiment is replacing its current Inner Detector with a new all-silicon Inner Tracker (ITk). The ITk will feature an active sensor area of 165 m², with its outer tracking layers populated by approximately 20,000 ATLAS18 n⁺-in-p silicon strip sensors manufactured by Hamamatsu Photonics K.K. (HPK) and glued-on hybrids carrying the front-end electronics necessary for readout. The silicon sensors, available in eight shapes tailored for barrel and endcap modules, are designed to tolerate fluences of up to 1.6 × 10¹⁵ neq/cm² and ionizing doses of 66 MRad.
A comprehensive, multi-year Quality Control (QC) program is underway across multiple international institutes to evaluate these ITk strip sensors for mechanical and electrical conformity. The QC process includes IV/CV characterization, full strip tests, long-term current stability monitoring, visual inspection, and metrology tests. To manage the high throughput of about 500 sensors per month, the collaboration has implemented standardized test procedures, software packages, unified data formats, and automated analysis tools. The standardization ensures consistent pass/fail evaluation and centralized data handling that enables effective identification of trends and anomalies at all sites during multi-year production.
This contribution will present an overview of the ITk strip sensor production and QC framework, along with key findings through the whole production such as charge-up of sensors, stability of the leakage currents, nonrecoverable I-V breakdown, and low inter-strip isolation. It will provide insights into sensor yield, quality trends, and review specific case studies, such as p-stop doping non-uniformity. Over 86% of the production, totaling over 530 batches, are tested and accepted as-is. Six batches are rejected: two due to instability and non-recoverable I–V breakdown, and four due to non-uniform p-stop doping. Additionally, 1.8% of individual sensors are rejected after visual inspection, non-recoverable I–V breakdown, and other issues. In total, 2.9% sensors were rejected, including both individual sensor rejections and batch rejections.

Speaker: Pavla Federicova

Abstract_HSTD14-Federicova.pdf

76 Research of the impact of electrostatic charge on the surface of silicon strip sensors

The Alpha Magnetic Spectrometer (AMS-02) is a particle detector that operates on the International Space Station (ISS), aiming to search for antimatter and dark matter by performing precision measurements of cosmic ray composition and flux. In order to increase physics sensitivity, a new layer(L0) of silicon strip tracker was planned to be installed on top of AMS-02 to improve cosmic ray acceptance and heavy ions resolution. This tracking layer consists of two planes of silicon strip detectors, each composed of 36 units called "ladders". Each ladder is composed of a readout PCB board and 8, 10, or 12 silicon strip sensors. During the construction and quality control phases of the ladders, we observed that electrostatic charges on the passivation layer of silicon strip sensors can significantly increase the electronic noise level of the affected readout channels.

Firstly, we introduce the design of the silicon strip detector sensor and the ladder. Then, how we mimic the procedure to generate electrostatic charge on the surface of the sensor is presented. Detailed measurements of the readout electronics noise level and charge collection efficiency were carried out for normal and contaminated channels. The TCAD simulation of the silicon strip sensor and the SPICE simulation for readout circuits were used to help understand the mechanism of the impact of the static charge on the detector performance. And finally, the setups for eliminating the effect on the strip sensor will be shown.

Speaker: Qinze Li (Institute of High Energy Physics (IHEP), Chinese Academy of Sciences)

77 Evaluation of Radiation-Tolerant Photodiodes for CMOS Image Sensors

Radiation-hardened CMOS image sensors are critical for surveillance in nuclear facilities and other high-radiation environments. Under such application conditions, ionizing radiation may rapidly degrade the photodiode performance and significantly compromise the sensor’s imaging capability. In this study, radiation damage effects on photodiodes are reviewed, and several radiation-tolerant photodiode structures are discussed, including diodes with gate-overlap, P+ surrounding, and integrated N+ drains. By modeling the effects of radiation-induced defect densities on internal electric fields and potential barriers, TCAD analysis explains the fundamental principles of radiation-tolerant photodiode structures. Impacts on sensor performance with different geometric parameters, such as overlap length, drain shape, and N-well variants are carefully evaluated with TCAD simulation. Prototype sensors implementing these designs are fabricated and characterized before and after exposure to high total-ionizing-dose irradiation. Preliminary test results will be presented and further optimizations will be discussed.

Speaker: Mr J. Deng (School of Physics, Zhejiang University, Hangzhou, 310058, China)

78 Impact of radiation damage to the performance of depleted monolithic active pixel sensors for Belle II vertex detector upgrade

The Belle II experiment is currently recording data from $e^+e^-$ collision at the SupperKEKB accelerator, which holds the world's highest luminosity of $5\times10^{34}~\mathrm{cm^{-2}s^{-1}}$ and will be upgraded to achieve a higher luminosity of $6\times10^{35}~\mathrm{cm^{-2}s^{-1}}$. An R&D program has been established to develop a new vertex detector (VTX) the one currently operating in Belle II. This upgrade will enable the experiment to cope with the higher hit rate and radiation level at the target luminosity while maintaining excellent tracking performance.

The VTX is a pixelated detector with 6 straight layers, whose radii range from $14~\mathrm{mm}$ to $140~\mathrm{mm}$, matching the radial acceptance of the current vertex detector, with minimal material budget. The layers are equipped with identical CMOS Depleted Monolithic Active Pixel Sensors (DMAPS), OBELIX, which is developed based on the TJ-Monopix2 DMAPS prototype. The pixel matrix design of OBELIX is the same as that of TJ-Monopix2 while the digital logic has been modified to adapt to the Belle II experiment, enabling a trigger rate of $30~\mathrm{kHz}$ with $10~\mathrm{\mu s}$ latency. The VTX must be able to cope with a high average hit rate of up to $120~\mathrm{MHz \cdot cm^{-2}}$ and endure high irradiation, with accumulated TID of $100~\mathrm{Mrad}$ and NIEL flux of $5\times 10^{14}~\mathrm{n_{eq}cm^{-2}}$. While the design of the minimal material budget detection layers is on-going, it is critical to assess the maximum operation temperature at the expected maximal radiation.

This presentation will describe the main VTX concepts for the sensor and the detection layer design. Then, measurements of the detection performance on TJ-Monopix2 samples irradiated with electrons and protons will be reported, in order to confirm the good performance of VTX detector after being irradiated in its long-term operation. As a result, even though degradation of detection efficiency is seen, it is confirmed that the detection efficiency can be recovered back to more than $99\%$ with high bias voltage and configuring with low detection threshold. Besides, milder radiation damage is seen with electron-irradiation compared with proton-irradiation.

Speaker: Shijie WANG (UTokyo)

12:10 Lunch Tue

5. Radiation Effects on Detectors: Tue-3

79 Evaluation of post-irradiation performance of strip sensors affected by low p-stop issue

During the production of the new ATLAS Inner-Tracker (ITk) strip sensors for the forthcoming High-Luminosity Large Hadron Collider (HL-LHC) upgrade, the collaboration observed indications of low p-stop doping in a few sensor batches. Quality Control measurements of full-size sensors from these batches showed indications of sensor areas with low inter-strip isolation. Detailed studies of Quality Assurance test structures, such as MOS capacitors with p-stop or Punch-Through Protection structures, confirmed the deviation of parameters dependent on the p-stop doping, showing also inhomogeneity within some of the wafers. Although these sensor batches were identified and rejected, the performance of sensors with low p-stop doping after irradiation needs to be evaluated in detail to understand the possible consequences in HL-LHC working conditions.

This work presents a complete characterization of the inter-strip characteristics of full-size and miniature ATLAS ITk strip sensors irradiated with gammas and neutrons, covering a wide range of doses and fluences to disentangle the influence of the ionization and displacement damages on the defective p-stop isolation. The radiation levels ranged from one equivalent to the first days of the ITk detector in working conditions to the end of the 10-year lifetime of the experiment. The results are discussed in detail. The full-size sensors show a clear decrease of the inter-strip resistance for the sensors with low p-stop doping at all irradiation levels. Also, results from miniature sensors irradiated only with gamma doses show that miniature sensors with low p-stop doping reach values below the ATLAS specifications much earlier than standard miniature sensors with normal doping. In contrast, we observe that neutron irradiations increase the inter-strip resistance values for fluences above 4e14 neq/cm2, suggesting that displacement damage dominates over ionization impact for fluences accumulated after only a few months in working conditions, improving the inter-strip isolation and compensating for the deficiencies of low p-stop doping.

Speakers: Javier Fernandez-Tejero (Institut de Microelectrònica de Barcelona (IMB-CNM, CSIC)), Miguel Ullan (Centro Nacional de Microelectronica (IMB-CNM, CSIC))

80 Radiation Effects on Surface and Bulk Properties of ATLAS18 Miniature Strip Sensors: Insights from Low-Dose Gamma Irradiation and Annealing Studies

Silicon strip detectors developed for the Inner Tracker (ITk) of the ATLAS experiment are designed to operate in the harsh radiation environment of the HL-LHC accelerator. In the strip region of the ITk, sensors must withstand a total fluence of $1.6 \times 10^{15}~\text{n}_{\text{eq}}\text{ 1 MeV}/\text{cm}^2$ and a total ionizing dose (TID) of $66~\text{Mrad}$. To meet these requirements, radiation-hard $n^+$-in-$p$ sensor technology has been implemented in the ATLAS18 silicon strip sensors currently under production. The radiation tolerance of these sensors was verified through extensive irradiation studies conducted during development, including exposures to various particle types and energies. These studies were performed up to the maximum expected fluence and TID levels to ensure end-of-life operations.

This work delivers a comprehensive investigation of radiation-induced effects, using the miniature sensors in the ATLAS18 production wafers, irradiated with a $^{60}$Co $\gamma$-source to multiple low TIDs, ranging from $0.5$ to $100~\text{krad}$—levels highly relevant for the initial operating phase of the ITk tracker. Post-irradiation characterization included detailed measurements of total, bulk, and surface currents as functions of dose, temperature, and annealing regimes. Changes in full-depletion voltage and effective dopant concentration were extracted from capacitance–voltage analyses performed over the same parameter space. To investigate the thermal stability of radiation-induced bulk and surface defects, as well as to investigate their properties, isochronal annealing was performed from $80~^\circ\mathrm{C}$ to $300~^\circ\mathrm{C}$ and at a fixed temperature of $160~^\circ\mathrm{C}$.

The surface current showed a strong nonlinear increase with dose under the applied irradiation conditions and dominated the total current contribution over most of the TID range investigated. High-temperature annealing (above $\sim 250~^\circ\mathrm{C}$) reduced the total leakage current to pre-irradiation values, while the capacitance–voltage characteristics, and thus the full depletion voltage, remained essentially unchanged after irradiation and also after annealing. These results indicate that $\gamma$-radiation–induced defects in the mini sensors are predominantly surface-related and can be completely removed by sufficiently high-temperature annealing. This behaviour contrasts with earlier observations in high-dose ($630~\text{Mrad}$) irradiated diodes, where the bulk current increased linearly with dose and high-temperature annealing had little effect on the currents, but restored the full depletion voltage close to its pre-irradiation value. These observations are under investigation.

Speaker: Marcela Mikestikova (FZU, Czech Academy of Sciences)

81 New results on performance studies of the 3D modules at the test beam for the ATLAS ITk detector

For the High Luminosity upgrade of the Large Hadron Collider, the current ATLAS Inner Detector will be replaced by an all-silicon Inner Tracker (ITk). The installation is foreseen during the next LHC Long Shut Down 3 (2026-2030). The new tracker has been designed to face the challenging environment associated with the high number of collisions per bunch crossing and the expected large integrated luminosity. Therefore, ITk design has been optimized to maintain the current tracking performance but in such much more hostile environment. The ITk consists of a Pixel detector in the innermost part and a Strip detector in the outermost part. Both detectors are arranged in a central barrel section and two endcaps, to guarantee tracking hermeticity up to the very forward region of pseudorapidity 4.

Regarding the Pixel Detector, two different technologies have been chosen for the sensors: 3D and planar.
Due to their intrinsic radiation hardness, 3D pixel sensor have been chosen to instrument the innermost layer of the Pixel detector while the other layers will use planar sensors. Two pixel cells have been chosen according to the detector location: a 25x100 um2 rectangular cell for the barrel, and a 50x50 um2 squared cell for the end-cap, to optimize the ATLAS detector performance. The 3D sensors are produced by two vendors: Fondazione Bruno Kessler (FBK, Italy) and Stiftelsen for industriell og teknisk forskning (SINTEF, Norway). Each 3D sensor is hybridized to a readout chip to form the so-called single bare module, and three bare modules are then assembled by a flex circuit in a triplet module. This arrangement makes the 3D modules very different from the planar ones, in which a single large sensor tile is hybridized to four readout chips to form a quad module.

The 3D performance up to End of Lifetime (~1.7 10e16 neq/cm2) have been studied in R&D using preproduction parts on Single Chip Cards. Despite showing the excellent radiation hardness of the sensors, the main limitations of this approach have been the use of the readout chip ITkPixV1.1 that does not have the ability to read the ToT and the fact to test a single chip assembly only, rather than a final module. In this talk, we are showing for the first time results that overcome these limitations. We have built and tested in the laboratories triplet modules, thus formed by three single bare modules joint by a PCB, both with the preproduction readout ITkPixV1.1 and the production one, ITkPxV2. We have then irradiated few of them, at CERN IRRAD facility and at RARiS in Japan, and tested on a pion beam extracted by the CERN SPS.

We are therefore presenting for the first time the performance of these 3D triplet modules, in the final hardware configuration as they will be installed in the detector. We will present their efficiency as a function of the fluence and the charge collection as ITkPxV2 allows for the ToT measurement.

Speaker: claudia gemme (Istituto Nazionale di Fisica Nucleare)

82 Performance Study of Neutron Irradiated HV-MAPS

High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) offer nanosecond level timing in combination with a low material budget making them ideal for tracking detectors in high energy physics. With future experiments aiming for higher luminosities, the HV-MAPS technology has to satisfy strict requirements on time resolution and radiation tolerance.
One such experiment is the proposed LHCb Upgrade II which foresees the use of HV-MAPS in the main tracking system. To study the radiation tolerance of this technology, irradiation studies with different sensors and in particular with TelePix2 have been performed.

The TelePix2 is a full-size HV-MAPS implemented in the 180 nm HV-CMOS process of TSI Semiconductors. It was developed for and is in active use as region-of-interest trigger and timing layer for the beam telescopes at the DESY test beam facility. Each pixel of TelePix2 consist of a large-fill factor deep n-well diode that integrates a charge‑sensitive amplifier and a comparator. The discriminated hits are read out at 1.25 Gbit/s via a hit driven column-drain architecture.
To evaluate their radiation tolerance, TelePix2 sensors have been irradiated with neutrons up to $1\times 10^{15} \,\mathrm{n_{eq}/cm^2}$. This talk will present measurements of the IV-characteristics and the effective detection threshold following irradiation, as well as beam test results on hit detection efficiency and time resolution.

Speaker: Lucas Dittmann (Heidelberg University)

15:20 Tea

6. Radiation Tolerant Materials: Tue-4

83 Irradiation study of a high voltage monolithic pixel sensor in 55nm technology

The High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) become an attractive technology option for tracking detectors in high energy physics. This technology combines sensor and readout electronics in a single chip, making it compact and efficient. The development of HVCMOS sensor has mainly been implemented with 180 nm or 130 nm technology in the past decades.
To explore the small node technology of next generation HVCMOS sensors, a prototype chip has been fabricated for Multi Project Wafer (MPW) running with 55 nm HVCMOS technology and low resistivity for next-generation particle detectors.
To assess radiation hardness, the chips have been irradiated with 80 MeV protons at room temperature using the Chinese Spallation Neutron Source facility. The irradiation study focused on evaluating key operational parameters such as leakage current, signal-to-noise ratio, and charge collection efficiency under increasing irradiation dose.
In this article we present the detailed design of this 55nm HVCMOS pixel sensor, discusses its performance based on radiation test and compare the performance with non-irradiated sensors.

Speakers: Mr Cheng Zeng (IHEP (Institute of High Energy Physics), CAS), Mingjie Feng (IHEP (Institute of High Energy Physics), CAS), Zhiyu Xiang (IHEP (Institute of High Energy Physics), CAS)

Abstract HSTD.docx

84 A radiation tolerant particle detector with CIGS

Silicon is widely used as a sensor material in a broad range of imaging applications. In recent high-energy and high-intensity beam experiments, however, a high level of radiation tolerance has become essential. As a result, new semiconductor detectors composed of radiation-hard materials have been actively investigated. The Cu(In,Ga)Se₂ (CIGS) semiconductor is expected to offer excellent radiation tolerance, with the capability to recover from radiation-induced damage through the compensation of defects by ions.
In our study, we successfully detected Xe ions using a fabricated CIGS detector and confirmed that radiation damage could be mitigated through heat treatment. Furthermore, we investigated the recovery mechanism by measuring defects using Deep Level Transient Spectroscopy (DLTS).
Until now, our work has focused on CIGS samples with thicknesses of 2–5 $\mu$m, which are insufficient for depositing enough energy to detect a single charged particle. Recently, we successfully fabricated a 25 $\mu$m-thick CIGS sample, and its performance under Xe ion irradiation closely matched expectations.
This presentation will cover the development of the CIGS particle detector and highlight recent advancements in its performance.

Speaker: MANABU TOGAWA (KEK, High Energy Accelerator Research Organization)

85 Radiation tolerance of a diamond radiation detector for space use

A diamond radiation detector based on a diamond semiconductor has been developed as part of a 3U CubeSat project aiming to measure charged particles (≥ 10 keV) escaping from the Earth’s atmosphere along geomagnetic fields. Diamond is known as an excellent material for semiconductor devices because of a bandgap of 5.5 eV and a carrier mobility of 4000 cm²/Vs at RT. Additionally, diamond is expected to have high radiation tolerance. To evaluate the radiation tolerance of our diamond radiation, we conducted proton irradiation tests in The Wakasa Wan Energy Research Center with a total fluence of 8.89 × 10⁹ protons/cm², equivalent to 10 years of exposure in a sun synchronous polar orbit at 600 km altitude. The detector used in these tests is a single-crystal chemical vapor deposition diamond produced by Element Six Corporation, with a size of 2.0 × 2.0 × 0.5 mm³. We evaluated the detector’s spectroscopic performance by measuring linearity and energy resolution using characteristic X-rays from radioisotope sources of $^{241}\mathrm{Am}$, $^{133}\mathrm{Ba}$, and $^{109}\mathrm{Cd}$. We found that the energy resolution and linearity do not degrade within ranges of 11.2 % and 1.2 %, respectively. These results indicate that the diamond detector has high radiation tolerance, making it suitable for space use.

Speaker: Mr Yoshiyuki Ando (Kanazawa university)

attachment.pdf

Welcome: Tue night tour

Wednesday 19 November

2. Avalanche-based Sensors: Wed-1

86 Towards a 20 ps timing detector with hybrid and CMOS monolithic LGADs for the future ALICE 3 experiment at LHC

In the dynamic realm of silicon detector advancements, the pursuit of consistently improved timing precision has witnessed remarkable progress. However, the ambitious requirements of next-generation experiments, along with the broader impact on various future scenarios, such as, for example, the FCC-ee, have motivated substantial and dedicated R&D to unlock their full potential. In the context of the future ALICE 3 experiment (planned to be installed at the CERN-LHC during LS4 in 2034-35), an intensive research program is actively addressing the challenge of identifying a 20-picosecond sensor technology for the Time-Of-Flight detector.
This talk will present key results and next steps in the development of both traditional and monolithic Low Gain Avalanche Detectors (LGADs and CMOS-LGADs).

Comprehensive studies were conducted on progressively thinner LGAD, testing the first 15 μm sensors ever produced by FBK (Fondazione Bruno Kessler), Trento, Italy. The results highlighted the potential of a thinner design for improved timing performance, and a resolution below 20 ps was achieved. To address the challenge of a small signal at the input of the front-end electronics, the novel double-LGAD concept was introduced and tested for the first time. Additionally, studies on the impact of particle incidence angle provided important insights for detector design. The results of this R&D campaign, which highlighted the outstanding performance of LGADs in the different layouts and led to sensors matching the ALICE 3 requirements, will be presented.

Furthermore, extending the LGAD concept to a CMOS technology has the potential to offer a transformative path forward. A CMOS-LGAD design would allow to combine precise timing and full-area coverage in a monolithic approach, offering a simpler and cost-effective assembly. The first CMOS-LGAD prototypes were produced in the third ARCADIA engineering run using the 110 nm technology of LFoundry and were tested for the first time. The first production batches, with low gain, served as a valuable reference for subsequent sensor optimization strategies. Following these developments, the most recent produced CMOS-LGAD, showing a gain up to 14, reached an intrinsic sensor time resolution of 75 ps. Latest results and next steps toward the 20-ps goal will be discussed.

Speaker: Sofia Strazzi (University and INFN Bologna)

AbstractHSTD14_StrazziSofia.pdf

87 Radiation effects in 4H-SiC PN diodes, LGAD sensors, and MOSFET transistors

The wide bandgap 4H-SiC semiconductor material exhibits several intrinsic properties - namely, excellent radiation hardness, thermal stability, and high breakdown voltage - that make it a promising candidate for deployment in high-radiation environments. Recent advances in its industrial-scale production have further enhanced its attractiveness for high-energy physics applications.

This contribution presents an overview of the development and characterization of $\mbox{4H-SiC-based}$ sensors produced by the onsemi company based in the Czech Republic. The study includes the evaluation of 4H-SiC PN diodes and Low Gain Avalanche Detectors (LGADs) featuring an internal charge multiplication layer. Electrical and detection characterization covers the dependence of reverse leakage current and bulk capacitance on the applied depletion voltage, internal gain measurements using UV light sources, and the first Transient Current Technique (TCT) and beta source studies employing UV lasers and $^{90}$Sr source, respectively.

Radiation tolerance was assessed through irradiation of 4H-SiC PN and LGAD samples with 24 GeV protons at CERN IRRAD facility and gamma particles from the $^{60}$Co source at UJP Praha a.s., reaching total fluences and ionizing doses up to 5.2E15 1 MeV n$_{eq}$/cm$^2$ and 2.5 MGy for protons, and 0.3 MGy for gamma particles. Additional insight into radiation-induced effects was gained by subjecting the biased 4H-SiC MOSFET transistors to 24 GeV protons and $^{60}$Co gamma particles. The obtained results provide new perspectives on the radiation hardness of 4H-SiC devices and underscore their potential for future use in demanding environments typical for next-generation high-energy physics experiments.

Speaker: Jiri Kroll (Institute of Physics of the Czech Academy of Sciences)

88 4D-Tracking with DC-coupled Resistive Silicon Detectors (DC-RSDs)

Resistive Silicon Detectors (RSDs) are a recent innovation in the field of silicon sensors for 4D-tracking applications. The RSD design combines the LGAD technology with resistive read-out, yielding fast and large signals which are shared between multiple read-out pads. Thanks to their characteristics, RSDs can accurately reconstruct the hit position of an ionizing particle, achieving a spatial resolution equivalent to 4-5 % of their pitch. RSDs can thus provide the same spatial resolution as a traditional pixel detector with up to 100 fewer read-out channels: such an improvement leads to a drastic reduction in power consumption and cooling requirements, providing at the same time large pixels with plenty of space for the front-end electronics. On top of that, the RSDs feature an excellent timing resolution of 30-40 ps, making them very promising sensors for 4D-tracking applications.

This presentation will introduce, in particular, the latest evolution of the RSD design, the DC-coupled RSD (DC-RSD). In such a design, the read-out pads are DC-coupled to the resistive layer where the signal sharing happens, differently from the first RSD version (AC-RSD). In this improved design, the signal spreads over a well-defined area and is always seen by a predetermined number of read-out pads, and signals are short (1-2 ns). DC-RSDs, therefore, feature a very uniform spatial resolution and are suited for operation in high-rate environments.

After a brief introduction to DC-RSD, the talk will focus on recent test beam results obtained at DESY (5 GeV/c electrons) and CERN SPS (120 GeV/c hadrons) with DC-RSDs manufactured by FBK. Results from a variety of DC-RSD designs, featuring different geometries and pitches, will be presented, offering a thorough overview of the production and its performance. As an example, a 300-µm pitch DC-RSD achieved a spatial resolution of ~12 µm and a temporal resolution of ~40 ps.

A highlight of the talk will be the use of an innovative technique based on a Deep Neural Network (DNN) to reconstruct the position and timing of the particle hit, instead of the standard techniques, which rely on analytical sharing laws. The advantage is that the DNN takes the raw signals (i.e. a set of voltage values separated by a fixed time interval) as input, whereas the analytical laws make use of high-level variables (amplitude, area) which require a sophisticated offline analysis. It will be shown that, with the DNN approach, it is possible to envision a front-end electronics that reconstructs both the position and timing of the hit by sampling the DC-RSD signals multiple times. Such an advancement represents a key step towards the future development of a real 4D-tracker based on RSDs.

Speaker: FEDERICO SIVIERO (INFN Torino)

89 Evaluation of dopant removal to design innovative LGADs: measurements and simulations

While the acceptor removal mechanism in standard n-in-p Low-Gain Avalanche Diodes (LGADs) is well understood and recognised as a key factor limiting their operational lifespan, the emergence of next-generation LGADs, such as resistive (RSDs) and compensated LGADs, calls for a deeper investigation into the donor removal mechanism, particularly at high initial donor concentrations (N_D > 10¹⁶ atoms/cm³).
In this contribution, we present pre- and post-irradiation results from a novel LGAD batch with an n-type doped gain implant on an n substrate (NLGADs), developed by Fondazione Bruno Kessler (FBK, Italy). These results offer new insights into donor removal, facilitating optimisation of RSD and compensated LGAD designs. Furthermore, this work introduces a novel characterisation method of dopant removal, based on sheet resistance measurements using van der Pauw structures, rather than traditional capacitance-based approaches.
Therefore, we will present comparative measurements and simulations for test structures and sensors from AC-LGAD (or RSD), DC-RSD, compensated LGAD, and NLGAD batches, highlighting the correlation between resistance- and capacitance-based removal assessments and their potential as characterisation tools for donor and acceptor removal. Preliminary data indicate a stronger donor removal coefficient compared to the acceptor removal coefficient. The upcoming results will be detailed in the final paper.

Speaker: Dr Francesco Moscatelli (IOM-CNR and INFN of Perugia)

Summary_Hiroshima_2025_Moscatelli.pdf

10:20 Coffee

2. Avalanche-based Sensors: Wed-2

90 Why LGADs work?

LGADs are well known for their excellent temporal resolution, a feature often attributed solely to internal charge multiplication. However, if gain were the only contributing factor, LGADs would exhibit significantly worse timing performance than what is experimentally observed.

In reality, three additional effects—non-uniform ionization, space charge, and gain saturation—play a fundamental role in explaining the temporal resolution of LGADs.

In this contribution, I will review the physical mechanisms that govern signal formation in LGADs and compare experimental results with simulations performed using the Weightfield2 program, demonstrating how each effect contributes to the overall performance.

Speaker: Nicolo Cartiglia (cartiglia nicolo)

91 Investigating the Proton Energy Dependence of Radiation Induced Gain Layer Degradation in Low Gain Avalanche Detectors

Low Gain Avalanche Detectors (LGADs) have been proven to be promising candidates for future high-energy physics (HEP) detectors, with their scheduled implementation in the HL-LHC timing layers of the CMS and ATLAS experiments. They feature a highly doped gain layer which creates a high electric field region, leading to amplification of the primary signal charge and therefore offering both precise time resolution and the ability to mitigate pile-up effects. Nevertheless, their performance under irradiation, especially the degradation of the gain layer and consequently loss of gain, remains a limiting factor for this technology. A detailed understanding of the degradation mechanisms, of which acceptor removal was identified as predominant process, is essential to optimize their design and functionality.
This study focuses on the radiation-induced degradation of LGADs subjected to proton irradiation across a wide energy range, from 18 MeV to 23 GeV. While the Non-Ionizing Energy Loss (NIEL) scaling hypothesis is commonly used to compare radiation damage across particle types and energies, it does not account for differences in the microscopic nature of the induced defects, for instance that low- energy protons tend to generate more point-like damage, whereas high-energy protons produce more clustered defects. These differences are expected to affect the degradation differently and lead to deviations from the NIEL scaling hypothesis.
The study includes a broad sample range of LGADs produced by Hamamatsu Photonics (HPK) and IMB Instituto de Microelectrónica de Barcelona (IMB-CNM), featuring design variations such as different gain layer depths and carbon co-implantation for defect mitigation. The devices were studied through I-V and C-V measurements, laser characterization, and signal response to a radioactive source. Obtained acceptor removal coefficients with proton energy indicate enhanced damage at low proton energies but also reflect a more complex dependence than a simple scaling with energy. Figure 1 (in the Attachements) shows measurements performed on HPK devices after irradiation with 18, 24, 400 MeV and 23 GeV protons. The legend gives the extracted acceptor removal coefficients. These findings provide input for refining radiation damage models and optimizing LGAD design for irradiation environments.

Speaker: Veronika Kraus (Vienna University of Technology, CERN)

Figure_1_acc_removal.pdf

92 Next generation TI-LGADs on Timepix4

In recent years, development of pixel detectors has evolved from only improving the spatial resolution to also improving the temporal resolution.

The ultimate goal is to develop a 4 Dimensional tracking (4D tracking) system capable of combining micrometer spatial resolution with a temporal resolution in the order of tens of picoseconds. Sensor types such as Low-Gain-Avalanche-Detectors (LGADs) provide a promising avenue for detectors with excellent time resolution due to their intrinsic gain. To achieve a good spatial resolution, segmentation into small pixels in the order of 50 micron is required. The introduction of trench isolation to the LGAD production process, producing the Trench-Isolated-LGADs (TI-LGADs), enables the technology to achieve the necessary segmentation for use in 4D tracking.

The first TI-LGAD production by FBK allowed for miniaturization of pixels down to 55 micron pitch. When connected to the Timepix4 readout ASIC, to form a fully hybridized system, the achieved time resolution was below $100\, \mathrm{ps}$. However, the gain region of the devices was limited to only the innermost 50% of the area. Second generation TI-LGADs, produced at FBK with the goal of increasing this gain region, have been hybridized using the Timepix4 readout ASIC in order to evaluate their performance.

In this contribution we will present recent test beam and lab results of second generation assemblies. Special attention is given to comparing the performance of these TI-LGAD devices, concerning active gain region and achieved timing resolution, to the first generation devices.

Speaker: Uwe Kraemer (Nikhef)

93 Development of Pixelated Capacitive-Coupled LGAD (ACLGADpix) Detectors

The Low-Gain Avalanche Diode (LGAD) is a semiconductor detector capable of achieving excellent timing resolution (~20 ps) for minimum ionizing particles (MIPs). To realize a pixelated detector with both high timing precision and spatial resolution, we have been developing Capacitive-Coupled LGADs (ACLGADs) for future collider experiments, such as the latter phase of the High-Luminosity LHC. We have successfully fabricated a pixelated ACLGAD (ACLGADpix) with a 100 $\mu$m × 100 $\mu$m pixel pitch, maintaining uniform timing performance across the active area.
In this presentation, we will report recent measurement results from ACLGADpix prototypes using beta rays, an infrared laser, and a 3 GeV electron beam. We will also discuss potential readout electronics for future collider applications.

Speaker: Koji Nakamura (KEK)

12:10 Lunch Wed

2. Avalanche-based Sensors: Wed-3

94 LGAD characterization for CMS ETL

During the High Luminosity phase of LHC, up to 140 - 200 proton-proton collisions per bunch crossing will bring severe challenges for event reconstruction. To mitigate pileup effects, an extended upgrade program of the CMS experiment is expected. Among these, a new timing layer, the MIP Timing Detector (MTD), will be integrated between the tracker and the calorimeters. With a time resolution of 30-60 ps, the MTD will enable 4D vertexing, bringing significant improvements in track-to-vertex association and object identification. The MTD is composed of two subsystems based on different technologies: the Barrel Timing Layer (BTL) consists of LYSO:Ce scintillating crystals readout by SiPMs, and the Endcap Timing Layer (ETL) is made of Low-Gain Avalanche Diodes.

The LGADs are an important development in silicon detector technology. They boast advantages such as excellent time resolution and signal-to-noise ratio, rendering them crucial for next-generation detectors. LGADs can be quickly evaluated for key electrical parameters—including breakdown voltage and depletion voltage—through I-V and C-V tests. These tests enable us to assess the quality of LGADs.

Measurements were conducted on a probe station, where single probes were used to connect the pad of the LGAD test structure. A Keithley 2470 high-voltage source meter supplied voltages ranging from 0 to 320 V in 5 V increments, with a protection current set to 5 microamperes. A Keithley 6482 picoammeter recorded current values at different voltages, generating I-V curves from which breakdown voltages were derived. Similarly, using the same probe platform, C-V curves of the pads can be measured, and 1/C²-V curves can be analyzed to determine the depletion voltage of the LGADs. A comparison between our measured breakdown voltages and the factory-measured breakdown voltages distribution revealed good consistency, confirming the accuracy and reliability of our test setup. For the sensor array, a 16×16 probe card was used to connect to the sensor, with a switch matrix board developed and employed to select each LGAD channel being measured while grounding the rest of the channels and the guard ring. The switch matrix board also reads and processes data from the probe card. The Keithley 2470 high-voltage source meter supplied voltages from 0 to 200 V with non-uniform step sizes, and the total protection current was set to 500 microamperes. Current measurements were taken using the Keithley 6482 picoammeter.

In summary, this talk presents the characterization in the laboratory of the extensive arrays of LGAD prototypes of 16x16 channels and test structures for the CMS ETL, including I-V and C-V measurement experimental setup and preliminary measured results.

Speaker: CMS Collaboration

95 Research of Low Gain Avalanche Detectors for High-Precision 4D Tracking in Future Collider Experiments

AC-LGADs (AC-coupled Low Gain Avalanche Detectors) have emerged as promising candidates for future 4D tracking systems, garnering significant attention from various research institutes. Studies on IHEP’s AC-LGADs, utilizing 50-µm-thick strip sensors, have demonstrated impressive timing resolution of approximately 40 ps and spatial resolution of around 10 µm. However, centimeter-scale strip AC-LGAD sensors face challenges such as charge sharing, increased capacitance, and other factors that can degrade spatial and timing performance while increasing power consumption. Addressing these issues requires optimization of the AC-LGAD fabrication process and structural design.

This work presents detailed simulations of AC-LGAD designs, focusing on key improvements to enhance performance. These include tuning the n+ sheet resistance to optimize charge sharing, modifying the isolation structure to reduce capacitance, and selecting appropriate coupling dielectric materials. Such advancements aim to position AC-LGADs as robust 4D tracking & time-of-flight (TOF) detectors for future collider experiments. The design of IHEP AC-LGAD strip sensors will also be presented. Additionally, the testing results of IHEP AC-LGAD strip sensors will be discussed in detail.

Speaker: Mei Zhao (IHEP)

96 N-type LGADs for Particle and Photon Detection

Low-Gain Avalanche Diodes (LGADs) are typically fabricated on p-type substrates, following an n–p$^+$–p junction configuration, where a boron-enriched layer forms the gain region.
This architecture is considered optimal for timing and particle-tracking applications, as the primary charge carriers initiating the avalanche process are electrons, which have a higher drift velocity and ionization coefficient compared to holes. However, for the detection of low-penetrating particles, such as soft X-rays, the conventional p-on-n configuration becomes less efficient. In these cases, most carriers are generated close to the front junction (n-type region) or within the high-field gain layer, resulting in reduced gain, lower signal-to-noise ratio (SNR), and decreased quantum efficiency (QE).
To overcome these limitations and improve the detection efficiency of low-energy photons and particles, LGADs on n-type substrates (N-LGADs) have been recently proposed. This inverted doping configuration, compared to standard LGADs, is expected to deliver higher gain and SNR for low-penetrating radiation, particularly for X-rays below 1 keV.
A new batch of N-LGADs was fabricated at FBK with a twofold objective: (i) to evaluate an optimized junction design for soft X-ray and low-penetrating particle detection, and (ii) to study donor removal effects under high-fluence irradiation. The latter is of increasing relevance for some emerging LGAD technologies, such as Compensated LGADs and Deep-Junction LGADs (DJ-LGADs), both of which rely on an n-type enriched gain layer. In these designs, accurate determination of the donor removal coefficient is a key parameter.
The fabricated N-LGADs employ 55 µm-thick n-type epitaxial substrates, with the front junction formed by boron ion implantation. Several junction depths and doping profiles have been implemented to investigate QE as a function of junction design. The gain layer has been doped with either Phosphorus or Arsenic to assess the donor removal coefficient for both species, and both deep and shallow gain layers were realized.
Electrical characterization (I-V, C-V and gain measurements) will be presented for the different technological splits, along with optical characterization in the 300–900 nm wavelength range. The latter enables determination of QE and gain as a function of the charge generation depth, providing a comprehensive comparison among the various device configurations.

Speaker: Giovanni Paternoster (Fondazione Bruno Kessler)

97 Performance of the sensors and electronics of the ATLAS High Granularity Timing Detector

The ATLAS High Granularity Timing Detector (HGTD) is a new detector subsystem that will instrument the ATLAS experiment for the High-Luminosity LHC (HL-LHC) phase in order to preserve the experiment reconstruction performance (and hence its physics potential) under the very high pileup (200 simultaneous proton-proton collisions at every 25ns) arising from the $7.5 \times 10^{34} \mathrm{cm}^{−2} \mathrm {s}^{−1}$ instantaneous luminosity expected during the HL-LHC operation. In order to enhance the sensitivity to physics process in the forward region, ATLAS will extend the rapidity coverage of its tracking system to |η| >4 through a new semiconductor tracking detector (ITk). However, separating the hard scatter from the pile-up requires a spatial resolution impossible to be attained at rapidities above |η| > 2.4 by ITk. By covering the rapidity range 2.4 < |η| <4 with 4 layers of Low-Gain Avalanche Diodes (LGAD), the HGTD will provide timing information with tens of picoseconds resolution and, through the use of a 4D-tracking approach, mitigate the effects of pile-up combining HGTD timing with ITk spatial information. The HGTD consists of two disks of 2 m diameter, symmetrically installed wrt the collision point. Around 3.6 million channels will be readout, covering an area of 6.4 m2 of LGAD sensors. This presentation will discuss the extensive research and development efforts undertaken by the HGTD project, including the design and characterization of the all new LGADs, demonstrating their timing performance and radiation hardness using high-energy particle beams, the development of a custom integrated readout circuit capable of precise time measurements and the integration of these components that encompass the HGTD system.

Speaker: Marco Leite (Universidade de São Paulo -USP)

15:20 Tea

7. Applications in Astrophysics, Biology, Medicine and Medical Equipments: Wed-4

98 Characterization of gallium-nitride-based particle detectors with pn-junction and low-gain avalanche diode structures

With the advancement of high-luminosity accelerator experiments, future hadron collider projects following the LHC are expected to require tracking detectors with radiation tolerance approximately ten times greater than the level at the high-luminosity LHC. Therefore, the development of semiconductor detectors capable of stable operation in such high-radiation environments is crucial to realize the future hadron collider experiments.
Two types of GaN-based detectors: p-n junction diodes (GaN-PND) and low gain avalanche diodes (GaN-LGAD) have been evaluated. The GaN-PND consists of a 550 nm p-GaN layer over a 10 μm n$^{-}$-GaN active layer. The GaN-LGAD has a similar structure but features a 250 nm n$^{+}$-GaN gain layer directly beneath the p-GaN layer, above a 10 μm n$^{-}$-GaN sensor layer. Pixel electrodes of 150 μm × 150 μm are used for signal readout.
We measured responses of GaN-PND and GaN-LGAD detectors with 5.4 MeV α-particles from $^{241}$Am and 170 MeV/n $^{132}$Xe$^{54+}$ ions, the latter of which were irradiated at the HIMAC, QST in Japan. We successfully achieved two-dimensional detection of these charged ions using GaN devices. In GaN-PND, the charge collection was measured as a function of bias voltage. Approximately 76 fC was collected for α-particles at a bias voltage of 200 V, and about 570 fC was collected for Xe ions at 160 V. In the case of GaN-LGAD, a collected charge of approximately 83 fC was obtained for α-particles at 200 V, and below this voltage, the behavior of charge collection was almost consistent with that of the GaN-PND. For Xe ions, a collected charge of about 94 fC was observed even at 5V.　Furthermore, we present results from the GaN-PND samples irradiated with 50 MeV protons at the RARiS, Tohoku University in Japan with fluences up to 1.1×10$^{16}$ n$_{\rm{eq}}$/cm$^{2}$.

Speaker: Mr Satoshi Iida (Univ. of Tsukuba)

99 Development of a high-contrast SPECT for small-animal imaging with high-energy gamma rays

In nuclear medicine, there is a growing need for imaging systems capable of visualizing gamma rays in the several-hundred keV range. One notable application is the imaging of radioactive gold nanoparticles, which emit 412-keV gamma rays. Although considered promising drug carriers, their biodistribution is not fully understood, making it important to visualize their distribution in animal experiments. However, high-resolution imaging devices for several-hundred keV gamma rays have not yet been developed. Single-photon emission computed tomography (SPECT) uses a gamma-ray detector with a collimator that limits the incident direction of photons. Although widely used in clinical practice, conventional SPECT typically has a spatial resolution of ~5 mm, which is insufficient for small-animal imaging. Moreover, SPECT is usually limited to photon energies below 200 keV, as high-energy gamma rays tend to penetrate the collimator walls. While thick collimator walls are required for high-energy photons, they significantly reduce the sensitivity of the system.
Therefore, we developed a high-contrast SPECT (HC-SPECT) for high-resolution imaging using high-energy gamma rays. The system employs a 1-mm pitch array of Gd₃(Ga,Al)₅O₁₂(Ce) (Ce:GAGG) scintillators coupled with a multi-pixel photon counter (MPPC) array. For whole-body imaging of mice, we assembled 10 × 10 cm² scintillator array and four 5 × 5 cm² MPPC arrays. To enable high-energy gamma-ray imaging, we also developed a novel collimator featuring hourglass-shaped holes, which are wider at the top and bottom surfaces and narrower in the middle. This design allows for thicker collimator walls while maintaining higher sensitivity than conventional parallel-hole collimators, enabling both high sensitivity and high resolution.
In this presentation, we will present performance evaluation results of HC-SPECT and compare its performance with that of conventional SPECT and a Compton camera, which is commonly used for high-energy gamma-ray imaging.

Speaker: Ms Nanase Koshikawa (Waseda University)

Appendix_NKoshikawa.pdf

100 Development of 2D SiPM-Based Photon Counting CT Using Newly Designed High-Performance ASIC Aimed at Preclinical Applications

Photon-counting computed tomography (PCCT) is a next-generation medical imaging technology that acquires spectral information by counting individual X-ray photons using energy thresholds. Current commercial PCCT systems use semiconductor detectors such as CdTe and CZT. Although, these detectors provide high energy resolution, they are limited by high cost and a lack of material flexibility. Additionally, charge-sharing effects significantly degrade the accuracy of spectral information. To overcome these limitations, we developed a 1D-64ch PCCT system incorporating a fast ceramic scintillator and a silicon photomultiplier (SiPM), and successfully demonstrated its usability through phantom experiments and in vivo imaging of mice injected with contrast agents.
　However, acquiring 3D images with a 1D sensor is complex and time-consuming. As the next step toward clinical application, it is therefore essential to demonstrate the feasibility of a 2D, large-area sensor. The implementation of a 2D sensor is expected to significantly reduce imaging time and facilitate dynamic imaging. In this study, we developed a new PCCT system incorporating a 2D, large-area sensor array and a newly developed, high-performance ASIC, which was specifically designed for scintillator-based PCCT by Hamamatsu Photonics. This ASIC is compatible with various scintillators and MPPC specifications. As a result of optimization, it achieved higher energy resolution (~33% FWHM at 59.5 keV) and more than twice the count-rate tolerance (>10 Mcps/ch) compared to our previous system. Furthermore, we successfully obtained 3D K-edge images of three contrast agents using six energy threshold images, demonstrating the system’s capability to accurately acquire spectral information.
　In this presentation, we will report on the performance evaluation and imaging results of the newly developed PCCT system.

Speaker: Takahiro Ro (Waseda University)

HSTD14_ro_supplemental_material.pdf

Welcome: Wed night tour

Thursday 20 November

7. Applications in Astrophysics, Biology, Medicine and Medical Equipments: Thu-1

101 Development and Performance Evaluation of INSPIRE: A Wide-Field Hybrid Compton Camera for Small Satellite GRAPHIUM

Waseda University and Science Tokyo are jointly developing GRAPHIUM, a 65 kg small satellite scheduled for launch in 2027. Its primary instrument, INSPIRE, is a box-type hybrid Compton camera operating in pinhole mode from 30 to 200 keV and Compton mode from 200 keV to 3 MeV. It achieves an angular resolution of 7.0°and an energy resolution of 7.5% at 662 keV, with an expected sensitivity comparable to COMPTEL. Its wide field of view, covering about one-quarter of the sky, enables the detection of unpredictable transient gamma-ray sources such as gamma-ray bursts. Observations of kilonovae from neutron star mergers could provide new insights into the origins of heavy-element nucleosynthesis. INSPIRE features a highly agile attitude control system, enabling rapid and flexible pointing toward targets including solar flares, active galactic nuclei (AGNs), and the Galactic center. A full-scale engineering model (EM) equivalent to the flight model was developed, and imaging tests using various radioactive sources were conducted. We also implemented a method for extracting individual spectra from multiple sources within the same field of view using Compton imaging, and successfully demonstrated its feasibility with the EM. To validate its mechanical robustness, vibration tests simulating Falcon 9 launch conditions were conducted using a partially equipped EM with mass-equivalent dummies. No performance degradation was observed before and after the tests, confirming structural integrity under launch conditions.

Speaker: Shojun Ogasawara (Waseda University)

Appendix_HSTD14_SOgasawara.pdf

102 AstroPix: High-voltage monolithic active pixel sensors for space-based experiments

AstroPix is a novel high-voltage monolithic active pixel sensor being developed mainly for future gamma-ray space telescope, AMEGO-X. It is also expected to be used in the barrel imaging calorimeter in the ePIC electron-iron collider detector, USA. AstroPix has to be 500 μm thick and to be fully depleted by supplying bias voltage. The energy resolution must be < 10% (FWHM) at 122 keV and the pixel pitch should be 500×500 μm2. The dynamic range should be in the range from 25 keV to 700 keV. Furthermore, given the space-based nature of AMEGO-X, the power consumption of AstroPix needs to be limited (< 1.5 mW/cm2). We have been developing four different versions of AstroPix so far. The first version of AstroPix was developed based on the experience of the developments of both MuPix and ATLASPix. It was used to understand the sensor and to develop the data acquisition tools. The second version has an increased pixel pitch and a digital readout capability. The third version, AstroPix3, reached the target pixel pitch with a moderate energy resolution of 6.2 keV (FWHM) at 60 keV.  The latest version of AstroPix, AstroPix4, is equipped with an improved time stamp generation and readout architecture to achieve 3 ns time stamping. Its power consumption is about 2 mW/cm2. The pixel capacitance is reduced by improving the routing and reducing the metal to n-well capacitance to achieve lower noise level. Thanks to it, most of pixels in a tested AstroPix4 chip detect 14 keV photopeak from Co-57, which could not be detected with AstroPix3. The mean energy resolution over the chip is 14% at 122 keV. The dynamic range is estimated to be in the range from 14 keV to ~250 keV. The bias voltage dependence of the measured depletion depth showed that the depletion depth growths as expected, but the achieved depth is only 90 um due to the fact that the resistivity of the used chip is not high enough to allow full depletion. We present an overview of our AstroPix development, selected results from AstroPix performance evaluations, design of the next version of AstroPix, and future prospects.

Speaker: Yusuke Suda (Hiroshima University)

103 X-ray Spectro-Polarimeters Enabled by Fine-Pixel CMOS Imaging Sensors

X-ray polarization provides unique insights into the geometry, magnetic field configuration, and emission mechanisms of high-energy astrophysical sources. While missions such as PoGO+, Hitomi/SGD, XL-Calibur, and NASA’s IXPE have demonstrated the scientific potential of X-ray polarimetry, there remains a need for instruments capable of simultaneous imaging, spectroscopy, and polarimetry with high spatial and spectral resolution in the medium and hard X-ray bands. We present the development of an X-ray spectro-polarimeter employing fine-pixel CMOS imaging sensors, optimized for the 6–30 keV range, which enables precise tracking of photoelectron trajectories via the photoelectric effect. Two sensor designs have been evaluated: a 2.5 µm pixel CMOS sensor (GPixel GMAX0505) and a 1.5 µm pixel CMOS sensor (Canon LI8020SA). Both offer low readout noise and enable accurate reconstruction of the initial photoelectron direction that encodes the incident photon’s polarization vector. The system is compatible with various optical configurations, such as X-ray reflection mirrors and coded aperture masks, both of which enable high-resolution imaging polarimetry. We have developed a dedicated FPGA-based digital readout and processing system, along with event reconstruction algorithms tailored for X-ray spectro-polarimetric measurements. To demonstrate the concept, beamline experiments using polarized synchrotron X-rays confirm modulation factors consistent with Geant4-based simulations. These experiments also allowed us to evaluate the quantum efficiency and energy resolution of the sensors. This technology offers a compact, low-power, and high-performance platform for future space-borne X-ray polarimeters, scalable from CubeSat-class instruments to larger observatories.

Speaker: Hirokazu Odaka (The University of Osaka)

104 Dark-current decrease of radiation-damaged SiPM at low temperature

SiPMs (MPPCs) have a <1cm small size with a low operation voltage <~50 V, which are suitable for radiation detectors onboard satellites with the limited space and power. However, after the radiation damage of 10 Gy/year caused by cosmic-rays, the SiPM dark current increases several orders of magnitude. In this presentation, we investigated the decrease of the dark current of radiation-damaged SiPM (S13360, Hamamatsu K.K.) at low temperature down to 100K. The SiPM was irradiated by 200 MeV protons with 10 Gy dose. The dark current decreased continuously as the temperature decreased <~1 $\mu$A at the break voltage +3V. The single photo-electron peaks were also visible at the lower temperature.

Speaker: Hiromitsu Takahashi (Hiroshima University)

10:20 Coffee

8. New Ideas and Future Applications: Thu-2

105 Development of a CCD-CMOS Hybrid Sensor for High-speed X-ray Imaging Spectroscopy in X-ray Astronomy

Current X-ray astronomical satellites carry CCD cameras that have moderate performance in imaging, spectroscopy and timing. Future X-ray telescopes with large effective areas and sharp point spread functions require quick readout of focal plane sensors to realize imaging spectroscopy without photon pile-up nor intermittency of its exposure time. To fulfill the requirements, we are developing a hybrid sensor of CCD and CMOS. The former has readout nodes for every column, and the latter equips corresponding columnar analog-to-digital converters. Both parts are implemented in the same package. Vertical transfer frequency of 100~kHz enables us to readout the whole frame within 10ms even with 1k-by-1k pixel format. Our first test device with pixel format of 128 x 1024 and pixel size of 11 um square has been cooled down to -23$^{\circ}$C and evaluated with monochromatic X-rays from $^{109}$Cd. X-ray events are successfully detected, and the energy resolution is 966eV (full width at half maximum) at 22 keV for the events whose signal charges are concentrated in a single pixel. This performance compares favorably with a conventional CCD with a thick depletion layer (750eV FWHM at 22keV @ -70$^{\circ}$C). On the other hand, approximately 30% of charges are lost for the multi-pixel events, which is probably due to a drain structure in every pixel for the case of charge saturation and can be omitted in the next fabrication.

Speaker: Hiroshi Nakajima (Kanto Gakuin University)

abstract.pdf

106 Development of an Electrical System for pnCCD onboard HiZ-GUNDAM with Integrated Charged-Particle Event Removal Algorithms

Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, releasing an enormous amount of energy on the order of $10^{52–54}$ erg lasting from tens of milliseconds to several hundred seconds, and are regarded as one of the most powerful probes for exploring the early Universe. HiZ-GUNDAM is a proposed future satellite mission aimed at investigating the early Universe (z > 7) using GRBs as probes, and consists of the wide-field X-ray monitor EAGLE and the near-infrared telescope MONSTER. EAGLE is an X-ray detector integrating Lobster Eye optics with pnCCD imaging sensors. It surveys a wide field of view (0.53 sr) in the soft X-ray band (0.4 – 4 keV) and determines the positions of detected GRBs with a localization accuracy of a few arcminutes.
In this study, we developed in-house pnCCD driving and readout electronics intended for satellite deployment. Using a pnCCD imaging sensor with a pixel size of 132 µm, an active area of 9.6 × 19.2 mm$^2$, and a depletion depth of 450 µm, we conducted X-ray imaging demonstrations using an Fe-55 radioactive source. The system consists of four types of custom-developed electronic boards, is designed to be lightweight and compact for spacecraft integration. Furthermore, our system incorporates an on-board function for autonomous real-time X-ray event extraction. In orbit, however, charged particles trapped by the geomagnetic field can produce background events in the pnCCD image sensors, which may result in false GRB alerts. In areas of intense charged-particle flux, such as the polar areas and the South Atlantic Anomaly, observations may be interrupted; however, to maximize observational efficiency, it is critical to efficiently remove charged-particle events while staying within the computational resources available for on-board processing. We evaluate and compare the background rejection performance and on-board implementation feasibility of multiple removal algorithms using X-ray data from an Fe-55 source and electron-event data obtained from an Sr-90 β-source. Preliminary results show that, under current test conditions, applying a machine-learning-based approach reduces the residual background fraction to about 3 %, indicating an improvement compared to conventional methods.

Speaker: Mr Ryuji Kondo (Kanazawa University)

additional_material.pdf

107 Monolithic integration of cooling microchannels in silicon wafers with BEOL layers

Future vertex colliders will require detector solutions that minimize material budget, which will be achieved by further integration of detectors, electronics and services. CMOS detectors have been proposed as a breakthrough solution for integration in particle physics experiments. The increased integration level combined with the subsequent higher channel density, and the high-performance processing of the sensor and electronics, will impose important challenges for the heat removal in these systems. Therefore, in order to build successful experiments, the cooling strategy will have to be considered from the beginning and will also need to comply with the low material budget and high integration level required for the whole system. Microchannel cooling has been proposed as a high efficiency, low mass, and high integration, heat removal method for detectors and electronics. Microfluidic cooling solutions have already been implemented in current experiments and in high performance computing (HPC) applications which make use of silicon cooling plates or cooling interposers attached very close to the detectors and electronics, which provide very high heat transfer efficiency and good integration features.

The next step in integration and heat removal capabilities is the full monolithic integration of the cooling microchannels in the CMOS substrate. Our work aims to this solution in which microchannels are incorporated in a ‘post-processing’ step to the CMOS detector substrate for particle physics applications. The work we will present here is a fundamental step in this direction, in which microchannels are incorporated in a “pure post-processing” way, to silicon wafers with aluminum tracks already created on them. This is a critical achievement because the Back-End of Line (BEOL) layers of the CMOS technology are the most sensitive to the processes involved in the creation of microchannels (DRIE or wafer bonding) due to the use of plasma processes, high pressures, high voltages, or temperature steps. Front-End of Line (FEOL) layers, like implants or isolation layers, as oxides or nitrides, are insensitive to these post-processing treatments. We will present the technological steps needed, the different technological options available, and the protective measures taken for the post-processing integration of cooling microchannels in silicon wafers with BEOL layers already present. We will also discuss the results obtained from the fabricated prototypes and the different challenges for the future monolithic integration of microchannel cooling in CMOS detectors.

Speakers: Javier Fernandez Tejero (Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC)), Miguel Ullan (Centro Nacional de Microelectronica (IMB-CNM, CSIC))

Abstract_monolithic-microchannels_HSTD14.pdf

11:50 Lunch/Excursion

Welcome: Dinner

Friday 21 November

8. New Ideas and Future Applications: Fri-1

108 Ultra-lightweight pixel tracker for the Mu3e experiment

The Mu3e experiment is on the frontier of charged lepton flavour violating searches and seeks to observe the rare muon decay $\mu^+ \rightarrow e^{+}e^{-}e^{+}$, as well as paving the way globally in terms of cutting-edge ultra low-mass detector technologies. Based at the Paul Scherrer Institute (PSI), a leading Swiss national laboratory near Zurich, the Mu3e experiment consists of four pixel tracking layers, as well as scintillator fibre and tile detectors.

The Mu3e outer pixel system is defined by three identical “stations”, one centred around the muon target, and one on either side known as the “recurl” stations. The central station will be built and operated first; and is scheduled to be installed in the beam area at PSI for data-taking in 2026.  The basic module building block of the pixel tracker system is known as a ladder, which consists of between 17 and 18 70$\mu$m thick HVMAPS MuPix 11 pixel sensors in the case of the layer 3 and layer 4 (outer) pixel detector layers, or 6 sensors in the case of layers 1 and 2. In addition to the sensors, the ladders consist of a $\sim 80 \mu$m thick aluminium/polyimide high-density interconnect (HDI) for the electrical connections and a mechanical support. Each of these layers are held together with minimal glue deposits, which are precisely controlled both in their placement location as well as the deposit amount. The radiation length of a 70$\mu$m  Mu3e outer pixel ladder is approximately 0.1% $X/X_0$. This ultra-lightweight detector design is driven by the need to minimise the dominant effects of multiple scattering and to achieve precise momentum resolution of less than 1 MeV. 

Electrical connections between the HDI, the sensors, and the read-out are achieved using single-point Tape Automated Bonding (spTAB). Over 1000 of these TAB bonds are required per ladder. Extensive electrical and thermo-mechanical tests have been undertaken to qualify the ladder objects as part of the QC/QA procedures before construction can commence. An innovative carbon-fibre geometry used solely for the outer pixel ladders has been custom-designed and will be presented in this talk. This mechanical support consists of 25$\mu$m uni-directional tow-spread carbon-fibre sheeting cured into a double-u shaped profile, with a 30-40% resin content and an 8$\mu$m kapton co-cured back layer for electrical isolation. The design considerations centre around the primary goal of ensuring maximum stiffness to protect the pixel sensors and improve ladder construction yield, whilst remaining extraordinarily lightweight. In total, 156 working ladders are required and are currently being built in the cleanroom in Oxford, each weighing only $\sim 2.5$ grams. The Oxford Mu3e group is responsible for producing all ladders required for the outer pixel tracking system, which includes fabrication of the carbon-fibre stiffeners. An overview of the ladder-building procedure will be presented, which includes a snapshot of various thermo-mechanical and ladder performance studies that have been performed in preparation for the now on-going production phase. Experience in handling ultra-thin silicon wafers as well as the performance of the MuPix 11 pixel sensors will also be presented.

Speaker: Ashley McDougall (University of Oxford)

109 The Pentadimensional Tracking Space Detector project, R&D for space-borne LGAD Si-microstrip tracking detectors

In the context of the Pentadimensional Tracking Space Detector project (PTSD), we are currently developing a demonstrator to increase the Technological Readiness Level of LGAD Si-microstrip tracking detectors for applications in space-borne instruments.

Low Gain Avalanche Diodes (LGAD) is a consolidated technology developed for particle detectors at colliders which allows for simultaneous and accurate time (<100 ps) and position (~ 10 μm) resolutions with segmented Si sensors. It is a candidate technology that could enable for the first time 5D tracking (position, charge, and time) in space using LGAD Si-microstrip tracking systems. The intrinsic gain of LGAD sensors may also allow to decrease the sensor thickness while achieving signal yields similar to those of Si-microstrips currently operated in Space.

In this contribution we discuss the ongoing activities for the design, development, and test of a breadboard laboratory model for verification of requirements, functionalities and space qualification of LGAD Si-microstrip devices for 5D tracking in space. We also present the study performed at the Italian Space Agency - Concurrent Engineering Facility (ASI-CEF) addressing the design of a LGAD-tracker flight-demonstrator to be housed in a 6U-XL CubeSat platform. The possible, successful operations in space of the demonstrator could confirm the TRL of Si-microstrip LGAD-trackers to 9, making it a viable and available technology for future mission opportunities for charged cosmic-ray and γ-ray instruments.

Speaker: Valerio Vagelli (Italian Space Agency (ASI, IT))

110 Characterization and Simulation for CASSIA: A CMOS Pixel Sensor with Internal Amplification

Future high-energy physics experiments require trackers with improved timing and spatial resolution, combined with a low material budget. The CASSIA (CMOS Active Sensor with Internal Amplification) project addresses these requirements by developing a monolithic pixel detector with internal amplification through the implementation of gain layers in an industrial 180nm CMOS imaging process.
The first prototype, CASSIA1, includes four 3×3 pixel matrices and 24 single-pixel structures without on-chip readout, enabling systematic studies of how geometrical parameters and variations in gain layer and electrode implantation profiles affect characteristics like sensor gain, breakdown voltage and dark count rate. The sensor can successfully be operated in LGAD mode as well as SPAD mode, allowing to target different HEP applications of the same sensor design.
CASSIA1 has been extensively characterized at regulated temperature in a climate chamber, and laser pulse measurements have been conducted to study the photo response. Sensor measurements and TCAD simulations are in good agreement and both are used to improve the design of the second prototype, CASSIA2. CASSIA2 will feature larger matrices with digital readout and analog readout, as well as multiple smaller test structures.
First results from CASSIA1 will be shown, which demonstrate the excellent performance of the first prototype sensor in terms of dark count rate, pulse amplitude, and operational range for LGAD mode and SPAD mode depending on sensor geometry and implantation profiles. The design of CASSIA2 will be introduced in the presentation, which aims at full fill factor while maintaining low dark count rate and integrating both analog and digital readout.

Speaker: Jenny Lunde (CERN)

Abstract_CASSIA_HSTD-14_final.pdf

111 Exploring the response of LGADs for time resolved synchrotron applications

The recent years have witnessed a growing interest in ultra-fast semiconductor sensors for time-resolved synchrotron light applications. Of special consideration are the Low Gain Avalanche Diodes (LGADs) which provide picosecond timing resolution and an internal gain mechanism, suitable to explore the fast repetition rates of hundreds of MHz and the high photon flux, low energy regime of the 4th generation synchrotron light sources. This work describes the recent results on the characterization of HPK LGAD 2x2 pads array prototypes performed at SIRIUS, the new Brazilian synchrotron light source,developed at the Center for Research in Energy and Materials (CNPEM) and operated by the National Synchrotron Light Laboratory (LNLS), where pulsed X-ray beams (10 ps width, 500 MHz repetition rate) with energies ranging from 6 to 12 keV and collimated from 300 $\mu$m down to 150 nm were used to extract the timing, energy response and gain of these devices under several operating conditions – such as temperature and operating bias voltage – using single and multiple pads response. Sensor signals were digitized by a fast oscilloscope triggered by a low jitter signal from the accelerator or by a coincidence from multiple photon conversions from an X-ray pulse happening at two adjacent pads in the array.

Speaker: Marco Aurelio Lisboa Leite (Universidade de São Paulo - USP)

10:20 Coffee

8. New Ideas and Future Applications: Fri-2

112 Low-Noise SiPM Light Readout and ASIC-Based Charge Readout of a Liquid Argon Time Projection Chamber for MeV Gamma-Ray Measurements

The Gamma-Ray and AntiMatter Survey (GRAMS) is a proposed mission to explore the MeV gamma-ray sky using a large effective-area Compton camera employing a liquid argon time projection chamber (LArTPC). As part of the concept study, we have developed a compact $5\times 5 \times 10\,\mathrm{cm^3}$ LArTPC prototype, named NanoGRAMS. When a MeV photon enters the LArTPC, it undergoes Compton scattering or photo-absorption in argon, producing scintillation light and ionized electrons. With information on the positions and energy depositions of these electron signals, we can estimate the spatial and energy distributions of incoming gamma rays.

NanoGRAMS is equipped with an arrayed silicon photomultiplier (SiPM) system, optimized for operation at liquid argon temperature ($87~\,\mathrm{K}$), for scintillation light detection, and a multi-pixel electron readout system. The SiPM system consists of $4\times 4$ array of $6\times 6\,\mathrm{mm^2}$ Hamamatsu SiPMs and a transimpedance amplifier. In liquid nitrogen tests ($77~\mathrm{K}$), the circuit demonstrated sensitivity from single photons up to approximately 100 photons with a timing response of nearly $80\,\mathrm{ns}$. This fast response is sufficient for not only event triggering but also rejection of background albedo neutrons through pulse shape discrimination. The electron readout system employs a 16x16 pixelated anode ($5.12\times 5.12\,\mathrm{cm^2}$) and ASICs originally developed for semiconductor detectors. In liquid argon, the electronics noise is 140 $\mathrm{e^-}$ rms per channel, which is sufficient for gamma-ray imaging. Combined with the SiPM light trigger, the system successfully detected energy depositions corresponding to multiple Compton scatterings from $^{60}\mathrm{Co}$ gamma rays ($1.17/1.33\,\mathrm{MeV}$). We present the design of the NanoGRAMS detector and the evaluation of gamma-ray measurement performance.

Speaker: Satoshi Takashima

113 TCAD Optimization and Validation of MAPS with Internal Low-Gain Amplification

Future tracking and vertex detectors require sensors with finer pitch, im-
proved timing resolution, and minimal power consumption. While monolithic
CMOS pixel sensors (MAPS) offer a promising solution, their performance is
somewhat limited by the small signal generated in their thin sensitive layers,
down to 10 μm in some technologies.
The APICS (Impact Amplification with CMOS Pixel Sensor) project inves-
tigates the use of internal low-gain amplification structures to enhance signal
levels and enable fast readout in small pitch designs. TCAD simulations are
used to design and optimize gain-layer doping profiles and electric field configu-
rations within a standard 180 nm CMOS imaging process. Simulations predict
a gain of around ×10 at 55 V. With such gain, the signal from minimum ionising
particles will exceed 0.7 V for an input capacitance of 2 fF, allowing to design a
compact and power-saving in-pixel front-end circuits. The target pixel pitch is
15 μm, supporting integration into sensors featuring about 1 Megapixel.
To validate the simulation framework, experimental data from the CASSIA
(CMOS Active Sensor with Internal Amplification) project at CERN was used.
The test chips developed within this project, fabricated in the same technology
and implementing similar gain structures but larger pitch, were characterized
through laser-based measurements. The measurements confirm gain onset and
signal behavior consistent with simulation, validating the TCAD optimization
approach.
These results help guide the design of two prototype chips, which are planned
for submission in the second half of 2025.

Speaker: Hasan Shamas (IPHC)

APICS_HSTD-14_Abstract.pdf

114 Characterization of Passive CMOS Strip Detectors after proton irradiation

Strip detectors are populating the outer trackers of high energy particle experiments. They are convenient for covering large areas of sensitive material since they use less power and have fewer readout channels compared to pixels sensors. Nevertheless, they are typically not manufactured using CMOS production lines since they have to be stitched along the implant of the strip and use several reticles to be connected together. For this project, strip detectors were fabricated in a CMOS foundry using different reticles to be stitched several times.

LFoundry produced passive CMOS strip detector using a production line with 150 nm technology, with 150 µm thickness FZ wafer. Those strip sensors have three different strip geometries to study different impacts of the CMOS technology on the strips. The strips have lengths of 2.1 cm and 4.1 cm, using 3 or 5 stitching reticles respectively. This work will show results of 24 GeV proton irradiated passive CMOS strip detectors. The detectors were irradiated at CERN and were tested with different setups, not showing any effect from the strips stitching.

Proving that this technology is feasible for detecting high energy particles opens the door to future large productions of passive CMOS strip detectors and also produce active strip detectors in a commercial foundry.

Speaker: Marta Baselga (TU Dortmund University)

Closure: remarks

12:10 Lunch / Fareware / guided tour