Speaker
Description
The next generation of IACT cameras is moving towards SiPMs for their stability, robustness, and higher sensitivity compared to PMTs. The Advanced SiPM Camera (AdvCam) is based on Silicon Photo-Multipliers (SiPMs) as photosensors and aims to deliver fully digital images downstream. It is designed to offer improved sensitivity, extended sensor durability, and intelligent data processing to more efficiently suppress background noise close to the detector level.
A 32-input channel ASIC is being designed using 65 nm CMOS technology. This ASIC, referred to as PRESSEC (Preamplifier Readout Electronics for Summing SiPMs Enhanced Circuit), has been proposed for the readout of large-area sensors. Its primary function is to provide an analog output by summing the signals from multiple sensors. An external ADC operating at 1 Gbps will be used for digitization. The PRESSEC provides accurate energy measurement by summing signals from four SiPMs into a differential output, thereby reducing the ASIC to 8 output channels. A pole-zero cancellation circuit is included to reduce the Full Width at Half Maximum (FWHM) of the pulse, minimizing pile-up effects from subsequent events. Additionally, a Night Sky Background (NSB) monitoring circuit measures unwanted events caused by moonlight or other ambient light sources. This circuit integrates detected events and can measure NSB rates from 1 MHz to 1 GHz, with a time constant ranging from 1 to 10 ms. To accommodate the large dynamic range required for NSB rate measurements, the ASIC employs a dual-gain structure with automatic switching controlled by comparators. Lastly, a trigger signal is provided at the output as the sum of all input signals for early event identification.
Several blocks are already complete at the schematic level, with layout implementation expected in early 2026. The energy readout achieves a signal-to-noise ratio (SNR) of at least 5 (linear), a dynamic range of up to 300 photons, a pulse width of 3–4 ns at FWHM, and a linearity error below 3% when tested with a Hamamatsu S13360-3075CS-UVE SiPM. Power consumption per input channel is expected to be below 10 mW. In addition, the NSB measurement circuit can accurately measure NSB fluxes up to 1 GHz with a linearity error below 2%.
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