A 0.22 nV/Hz, 4.5 mW/channel cryogenic amplifier for large arrays of SiPMs in liquid Argon

Several detectors for the next generation of particle physics experiments will make use of silicon photo-multipliers (SiPMs) to detect scintillation photons in liquid Argon. Cryogenic operation reduces dark counts by orders of magnitude, and makes it possible to retain single photon sensitivity even if large arrays of SiPMs are readout by a single amplifier. The total capacitance of a SiPM array with a total area of tens of cm2 can range up to 200 nF. The series noise of the amplifier is the dominant factor that determines the signal to noise ratio of the readout chain. In this contribution, we present a cryogenic amplifier designed to operate in liquid Argon. The base version has a series white noise of 0.37 nV/Hz, while dissipating just 2.4 mW. Design variants have been also tested, which reduce noise to 0.22 nV/Hz, with a power consumption close to 4.5 mW. The amplifier base design and variants have been tested reading out SiPM arrays consisting of up to 96 6 × 6 mm2 SiPMs, for a total photosensitive area of 35 cm2, demonstrating good single photon sensitivity even at low over-voltage values.