Progress in the development of large-scale MMC detector arrays

During the last decade low-temperature particle detectors like metallic magnetic calorimeters (MMCs) became interesting instruments for numerous experiments in atomic and nuclear physics, material science and X-ray astronomy. Since large detection areas, high count rates or especially imaging capabilities are often required, significant effort is put into the development of large detector arrays. To accommodate constraints on cryogenic wiring and to reduce parasitic heat load, sophisticated techniques for reading out large arrays with a small number of wires have to be designed. We discuss possible multiplexing techniques for MMCs and present recent results of the development of a frequency-domain multiplexed MMC detector array based on a dissipationless microwave SQUID multiplexer. This includes a systematic study of the properties of the fabricated superconducting CPW microwave resonators, a full characterization of the microwave setup and a preliminary design of a microwave rf-SQUID. We present performance tests of a single pixel MMC optimized for high-resolution X-ray spectroscopy and outline the properties of a room-temperature microwave electronics needed to read out a fully working MMC detector array.