EMI Susceptibility of a Differential Time-Division SQUID Multiplexing Circuit for TES Readout

Time Division multiplexing (TDM) using superconducting quantum interference devices (SQUIDs) is being developed to read out Transition-edge sensor arrays for the Athena X-ray integral field unit (X-IFU) and Cosmic Microwave Background Stage-4, which have baselined differential TDM architectures. We present the design of symmetric multiplexer circuit read out by a second stage SQUID series array amplifier (SSAA) that has differential input coils that reject the current response to common mode pickup. We present measurements showing that readout with differential input coils has lower EMI susceptibility than with single ended input coils. We also present increases in bandwidth and reductions in crosstalk enabled by related changes to the multiplexer circuit.