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Description
HEPS (High Energy Photon Source) is the first fourth-generation light source in China, featuring high-energy, high-luminosity X-rays. Since more than half of its end stations generate photon energies above 25 keV, high-Z detectors are essential. Additionally, advanced experiments such as X-ray Photon Correlation Spectroscopy (XPCS) and ultrafast dynamics studies necessitate detectors with high frame rates. To meet the demand for a high-speed, high-Z pixel detector at HEPS, a readout ASIC named HouYi has been developed
HouYi is a charge-integration readout chip operating in burst mode, designed for compatibility with electron-collecting sensors like CZT and CdTe. It features a pixel pitch of 150 μm × 150 μm, with an array size of 64 × 64 in the engineering run. The burst frequency is adjustable from 1 MHz to 4.7 MHz. To achieve both single-photon sensitivity and a high dynamic range, the chip incorporates a two-stage adaptive gain front-end circuit. Following charge integration, signals are stored in a 32-cell analog memory array, enabling successive sampling of 32 frames. The corresponding gain settings are also stored in analog form by converting a 2-bit digital gain signal into analog voltage levels. Finally, signals are read out via four differential drivers during the intervals between photon bunches.
HouYiV01S is the first small-scale prototype, containing a 32 × 32-pixel array with full functionality. Performance tests confirm its proper operation. The chip can integrate, store, and read out 32 pulses at frame rates up to 4.7 MHz. At a photon energy of 30 keV, the signal-to-noise ratio of the preamp exceeds 5, indicating the capability for single-photon resolution. The transfer characteristics of the dynamic range is approximately 4300 photons at 30 keV. The overall nonlinearity of the signal chain is below 4 %.