Development of Metallic Magnetic Calorimeters for High Precision Measurements of Calorimetric Re and Ho Spectra.

The measurement of calorimetric spectra following atomic weak decays, beta ( β) and electron capture (EC), of nuclides having a very low Q-value, can provide an impressively high sensitivity to a non-vanishing neutrino mass. The achievable sensitivity in this kind of experiments is directly connected to the performance of the used detectors. In particular an energy resolution of a few eV and a pulse formation time well below 1 μs are required. Low temperature Metallic Magnetic Calorimeters (MMCs) for soft X-rays have already shown an energy resolution of 2.0 eV FWHM and a pulse rise-time of about 90 ns for fully micro-fabricated detectors. We present the use of MMCs for high precision measurements of calorimetric spectra following the β-decay of Re and the EC of Ho. We show results obtained with detectors optimized for Re and for Ho experiments respectively. While the detectors equipped with superconducting Re absorbers have not yet reached the aimed performance, a first detector prototype with a Au absorber having implanted Ho ions already shows excellent results. An energy resolution of 12 eV FWHM and a rise time of 90 ns were measured. [ABSTRACT FROM AUTHOR]