Ionization Readout Electronics for SuperCDMS SNOLAB Employing a HEMT Front-End

Abstract

The SuperCDMS SNOLAB experiment seeks to deploy 200 kg of cryogenic Ge detectors employing phonon and ionization readout to identify dark matter interactions. One of the design challenges for the experiment is to provide amplification of the high impedance ionization signal while minimizing power dissipation and noise. This paper describes the design and expected performance of the ionization readout being developed for an engineering model of the SuperCDMS SNOLAB Ge Tower System. The readout features the use of a low-noise HEMT front end transistor operating at 4 K to achieve a power dissipation of 100 $\mu$W per channel, local grounding to minimize noise injection, and biasing circuitry that allows precise control of the HEMT operating point.