SQUID-based Readout Schemes for Microcalorimeter Arrays

Abstract. Microcalorimeter arrays with superconducting phase-transition thermometers are an attractive alternative for construction of imaging X-ray spectrometers. The low source impedance and low operating temperatures make dc SQUIDs good candidates for their preamplifiers. In large arrays, the circuit complexity as well as heat leakage through wiring make some sort of a multiplexing scheme desirable. Some circuit topologies for time-domain and frequency-domain multiplexing schemes are compared. One particular frequency-domain multiplexing circuit, being developed for the XEUS space mission, is reviewed in more detail. The design issues related with dynamic range, bandwidth and noise folding are discussed