Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 60: SC \& MLT: Cryodetectors
TT 60.6: Talk
Friday, March 18, 2011, 12:15–12:30, HSZ 301
Development of non-hysteretic unshunted rf-SQUIDs for multiplexed MMC readout — •S. Kempf, A. Fleischmann, L. Gastaldo, S. Heuser, A. Kampkötter, C. Pies, J.-P. Porst, P. Ranitzsch, S. Schäfer, S. Vick, T. Wolf, and C. Enss — Kirchhoff Institute for Physics, Heidelberg University.
Metallic magnetic calorimeters (MMCs) are energy dispersive particle detectors with a high resolving power that are operated at temperatures below 100 mK. Presently single channel MMCs are proving to be promising detectors in areas diverse as atomic and nuclear physics or x-ray astronomy, while many of those experiments would greatly benefit from large detector arrays. However, array readout poses a significant challenge since a multiplexing scheme is required. A promising approach employs a microwave SQUID multiplexer consisting of non-hysteretic unshunted rf-SQUIDs that are coupled to high Q tank circuits with unique resonance frequencies. By coupling all tank circuits to a common transmission line and injecting a microwave frequency comb it is possible to monitor all detectors simultaneously.
We discuss design, fabrication and operation of a microwave SQUID multiplexer for the readout of MMC detector arrays. For our present devices we used SNEAP to produce micron-size Nb/Al-AlOx/Nb Josephson junctions with low critical current densities. The quality of the fabricated Josephson junctions is discussed. Finally we outline the expected performance of a detector array that is read out with the designed SQUID multiplexer as derived from numerical optimization calculations.