Impedance Matching Between SQUID and Warm Amplifier for TES Readout in TDM for the ATHENA X-IFU Instrument

Current cryogenic instruments require an increasingly high number of superconducting detectors. Large multiplexing factors are thus needed, increasing the bandwidth of the readout signals. In the specific case of transition edge sensors (TES), a cold amplification stage using superconducting quantum interference devices is usually coupled to a room temperature low-noise amplifier (LNA). A resistive harness up to a few meters long connects these two stages carrying signals with bandwidth of up to a few tens of MHz. In this context, it is reasonable to consider the possibility of impedance matching at the input of the LNA. In this paper, we present the impact of such impedance matching for the ATHENA X-IFU instrument, which uses TES in time-division multiplexing (Barret in Exp Astron 55:373–426 2023).