Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 36: Superconductivity: Cryodetectors

TT 36.6: Talk

Thursday, March 29, 2012, 11:00–11:15, H 2053

Progress in the development of non-hysteretic rf-SQUIDs for a multiplexed MMC readout — •Sebastian Kempf, Andreas Fleischmann, Loredana Gastaldo, and Christian Enss — Kirchhoff-Institut für Physik, Universität Heidelberg.

Recently it was shown that the performance of single channel Metallic Magnetic Calorimeters (MMCs) meets the requirements of many applications like, for example, high resolution x-ray spectroscopy. Presently, a number of cryogenic multiplexing schemes are investigated to increase the channel count of MMC detector arrays significantly. A quite promising approach employs a so-called microwave SQUID multiplexer. Here, non-hysteretic unshunted rf-SQUIDs transduce the detector signals into a frequency shift of related superconducting microwave resonators with unique resonance frequencies. By injecting a microwave frequency comb and monitoring either phase or amplitude of each resonator, it is thus possible to infer the initial detector signals.

Based on experimental results obtained with our first prototype SQUID multiplexer and numerical simulations we optimized our current multiplexer design concerning rf-SQUID layout, SQUID-to-resonator coupling and fabrication of the Nb/Al-AlOx/Nb Josephson junctions. We discuss advantages of the modified fabrication process, differences between both multiplexer designs, the expected performance improvements and present first measurements of this second generation SQUID multiplexer.