Speaker
Description
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.
