Würzburg 2018 – scientific programme

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T: Fachverband Teilchenphysik

T 8: Neutrinophysik V

T 8.2: Talk

Monday, March 19, 2018, 16:20–16:35, Z6 - HS 0.001

Optimization of metallic magnetic calorimeter arrays with embedded ¹⁶³Ho for the ECHo experiment — Federica Mantegazzini and •Loredana Gastaldo for the ECHo collaboration — Kirchhoff-Institute for Physics, Heidelberg University, Germany

The ECHo experiment aims to determine the electron neutrino mass via the analysis of the calorimetrically measured electron capture spectrum of ¹⁶³Ho. The detector technology is based on metallic magnetic calorimeters (MMC) and the implantation of ¹⁶³Ho has been selected as method to enclose the source in the detectors, showing already good performances for activity values up to 1 Bq. Since the sensitivity of the ECHo experiment strongly depends on the total acquired statistics, the activity per pixel needs to be increased, taking into account two constraints: the resulting unresolved pile-up events fraction and the supplementary heat capacity due to the implanted ions. We have developed a novel experimental technique for the determination of the specific heat per ¹⁶³Ho ion, based on the simultaneous measurement of two MMC pixels with identical geometry which differ only because of the ¹⁶³Ho ions implanted in one of the two. At an operational temperature of 20 mK for an activity of about 1 Bq, the heat capacity increases of less than 3%. Therefore, a total activity of the order of 10 Bq per pixel - as required in order to keep the unresolved pile-up fraction under control - can be implanted without strongly affecting the detector performance. In this contribution, the development and the characterisation of the new microfabricated detector arrays is presented.