Frequency-Domain Multiplexed Readout for Superconducting Gamma-Ray Detectors

We are developing a frequency-multiplexed readout for arrays of high-resolution gamma detectors based on superconducting transition edge sensors (TESs). Each sensor is part of an LCR resonant circuit and is biased at an identifying carrier frequency. Several carrier signals are added and amplified with a single SQUID preamplifier at 4 K. Gamma absorption modulates the amplitude of the carrier, and demodulation at room temperature retrieves the initial temperature evolution of the sensor. This multiplexing system has originally been developed to read out large arrays of bolometers for cosmic microwave background studies. To accommodate the faster gamma-ray signals, its demodulator bandwidth is being extended to ~20 kHz to allow reading out up to eight TESs with a detector bandwidth of ~10 kHz. Here we characterize the system noise performance and show how this multiplexing scheme can be adapted to read out arrays of superconducting gamma-ray detectors.