Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 67: Cryogenic Particle Detectors and Other Superconducting Electronics

TT 67.1: Talk

Friday, April 5, 2019, 09:30–09:45, H4

Towards microcalorimetry with sub-eV energy resolution: Metallic magnetic calorimeters with direct sensor readout — •Matthäus Krantz, Andreas Fleischmann, Christian Enss, and Sebastian Kempf — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.

Metallic magnetic calorimeters (MMCs) are energy dispersive single particle detectors typically operated at temperatures below 50 mK. By using a paramagnetic temperature sensor strongly coupled to a matching absorber, state-of-the-art MMCs convert the energy input into a magnetic flux change that is measured by a current-sensing dc-SQUID via a superconducting flux transformer. However, transformer losses and parasitic inductances within the transformer result in a signal reduction ultimately limiting the achievable energy resolution. To challenge this limit we develop MMCs with direct sensor readout for enhanced signal coupling. There, the temperature sensor is placed on top of or within the SQUID loop. Our most recent prototype comprises a gradiometric meander-shaped SQUID inductance and gives reason to expect to significantly lower our current MMC world record energy resolution of 1.6 eV (FWHM) for soft X-rays. We describe the design, microfabrication and optimization of our prototype and discuss the presently achieved performance indicating that we will be able to reach sub-eV energy resolution in the near future.