Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 29: Poster Session: Cryogenic Particle Detectors and Cyotechnique

TT 29.6: Poster

Montag, 12. März 2018, 15:00–19:00, Poster B

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

Metallic magnetic calorimeters (MMCs) are energy dispersive particle detectors that are typically operated well below 100 mK. They make use of a paramagnetic temperature sensor to convert the energy deposited by an X-ray photon within an absorber into a change of sensor magnetization which can be precisely measured using a SQUID. For state-of-the-art detectors, the temperature sensor is transformer-coupled to the input coil of a current-sensing SQUID. However, parasitic inductances in the flux transformer, as well as transformer losses, lead to a reduction of the signal size, therefore impairing the energy resolution. For this reason we have started to develop detectors with direct sensor readout for which the temperature sensor is placed on top of the SQUID loop to maximize signal coupling. In our present design the SQUID is a first-order parallel gradiometer with meander-shaped SQUID inductance. Due to the greatly enhanced flux coupling as well as optimized SQUID parameters we expect this detector to surpass our current MMC world record energy resolution of 1.6 eV (FWHM) for 6 keV X-rays and push the present limit well below 1 eV. We discuss the optimization process, design and microfabrication processes as well as very recent results for these devices.