Frequency-domain multiplexed readout of transition-edge sensor arrays with a superconducting quantum interference device

Abstract

We demonstrate an eight-channel frequency-domain readout multiplexer for superconducting transition-edge sensors (TESs). Each sensor is biased with a sinusoidal voltage at a unique frequency. The sensor currents are summed and measured with a single superconducting quantum interference device (SQUID) array. The 100-element SQUID array is operated with shunt feedback electronics that have a slew rate of $1.2\times {10}^7{\Phi }_0∕\mathrm{s}$ at $1\mathrm{MHz}$ . The multiplexer readout noise is $6.5\mathrm{pA}∕\sqrt{\mathrm{Hz}}$ , which is well below the expected sensor noise of $15\mathrm{pA}∕\sqrt{\mathrm{Hz}}$ . We measure an upper limit on adjacent channel crosstalk of 0.004, which meets our design requirements. The demodulated noise spectra of multiplexed TESs are white at frequencies down to $200\mathrm{mHz}$ .