Impedance matching between SQUID and warm amplifier for TES readout in TDM

Abstract Current cryogenic instruments require an increasingly high number of super-conducting 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 (SQUIDs) 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 an ATHENA X-IFU like instrument.