A Single-Stage SQUID Multiplexer for TES Array Readout

We have developed a single-stage SQUID multiplexer (SQMUX) for time-domain multiplexing of transition edge sensors (TESs). The individual channels in our SQMUX circuit are SQUID series arrays (SSAs). Several of these SSAs form one column, of which exactly one SSA is active at a time. The channel to be read out is selected by setting a superconducting-to-normalconducting (SN) switch into its normalconducting state. All other channels are short-circuited by SN-switches in their superconducting state. This SQMUX topology ensures that there are no noise contributions from off-channels. The SN-switches employed are SSAs, as well. The addressing is performed inductively by means of coupling magnetic flux into the switch. Our SQMUX can be operated at the TES operating temperature. It is directly read out by a room temperature preamplifier. The first realizations of this single- stage SQMUX are 4:1 and 2:2 multiplexers. We present the application of the new SQMUX to read out TES X-ray microcalorimeters. Furthermore, we discuss the application of SQMUXs to the readout of distributed power TES Detectors.