Development of Superconducting Microresonators for a Neutrino Mass Experiment

The determination of the neutrino mass is still an open issue in particle physics. The calorimetric measurement of the energy released in a nuclear beta decay allows to measure all the released energy, except the fraction carried away by the neutrino: a finite neutrino mass m ν causes the energy spectrum to be truncated at Q − m ν , where Q is the transition energy. The electron capture of 163 Ho (Q ∼ 2.5 keV) results to be an ideal decay. In order to achieve enough statistics, a large number of detectors ( ∼ 10 4 ) is required. Superconducting microwave microresonators are detectors suitable for large-scale multiplexed frequency domain readout, with theoretical energy and time resolution of ∼ eV and ∼μ s. Our aim is to develop arrays of microresonator detectors applicable to the calorimetric measurement of the energy spectra of 163 Ho. Currently, a study aimed to the selection of the best design and material for the detectors is in progress. In this contribution, a comparison between the measurements (critical temperature, gap parameter, quasiparticle recombination time and X-ray energy spectra) made with stoichiometric, sub-stoichiometric TiN and Ti/TiN multilayer films are presented