Speaker
Description
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.
