Speaker
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. A die photograph is shown in Figure 1. Performance tests confirm its proper operation. As demonstrated in Figure 2, 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 10, indicating the capability for single-photon resolution. Figure 3 presents the transfer characteristics of the dynamic range, which extends to approximately 4300 photons at 30 keV. The overall nonlinearity of the signal chain is below 4 %.