Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 55: Poster Session: Superconductivity 2

TT 55.19: Poster

Wednesday, March 22, 2017, 15:00–19:00, P2-OG3

dc-SQUIDs for readout of metallic magnetic calorimeters — •Daniel Richter, Felix Herrmann, Anna Ferring, Andreas Fleischmann, Loredana Gastaldo, Sebastian Kempf, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany

Two-stage current-sensing dc-SQUIDs are presently the devices of choice to read out single-channel metallic magnetic calorimeters (MMCs). However, it is well known that parasitic inductances in the input circuitry lead to a reduction of the detecor signal size and that SQUID noise can cause a significant contribution to the energy resolution. In addition, parasitic mutual inductances between the input and feedback coil degrade the detector performance. In order to minimize these effects, we are currently developing two-stage current-sensing dc-SQUIDs that are optimized for MMC readout.

We discuss our different SQUID designs including single SQUIDs forming the front-end to the detector as well as N-SQUID series arrays providing signal amplification for the front-end SQUID at low temperatures. Our front-end SQUIDs are second-order parallel gradiometers, have an input coil inductance of about 1 nH and show a particularly small parasitic coupling between the input and feedback coil. Our N-SQUID series arrays provide an on-chip bias resistor and include all circuitry that is required for easily building two-stage SQUID setups. We will show that our two-stage SQUID setups exhibit a very good noise performance reaching values down to the quantum limit. This makes it ideally suited for readout of high-resolution MMCs.