Characterization of mini-CryoCube detectors from the Ricochet experiment commissioning at the Institut Laue-Langevin
2 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
3 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
4 NEEL - ElecLab - Electronique
5 NEEL - Cryo - Cryogénie
6 C2N - Centre de Nanosciences et de Nanotechnologies [Orsay]
7 Northwestern University [Evanston]
8 UMass Amherst - University of Massachusetts [Amherst]
9 University of Toronto
10 MIT - Massachusetts Institute of Technology
11 ILL - Institut Laue-Langevin
12 DLNP - Dzhelepov Laboratory of Nuclear Problems [Dubna]
13 NEEL - HELFA - Hélium : du fondamental aux applications
14 UMASS - University of Massachusetts System
15 Colorado School of Mines
Résumé
The Ricochet experiment aims to measure the coherent elastic neutrino-nucleus scattering process from antineutrinos emitted by a research nuclear reactor operated by the Institut Laue-Langevin (Grenoble, France). This article presents a description of the Ricochet experimental installation and the detector performance achieved during its commissioning with a mini-CryoCube module consisting of three 42-gram germanium cryogenic calorimeters. The baseline resolutions and background levels are reported both during reactor-on and reactor-off periods, and as noise mitigation techniques were improved. A baseline resolution of 40 eV electron equivalent was achieved for the ionization channel after setup improvements, and the phonon channel resolutions ranged from 50 to 80 eV of total phonon energy. In the energy region from 2 to 7 keV, a nuclear recoil rate of 15(2) events/(kg day keV) is measured during the reactor-off period selecting events in coincidence with muon veto signals. This rate is in agreement with the cosmogenic neutron rate calculated from GEANT4 simulations. After the rejection of events in coincidence with signals in the muon veto detectors, a combined 90% C.L. limit on the nuclear recoil background of < 9 events/(kg day keV) is obtained in that energy region during the reactor-on period, which is compatible with our GEANT4 model calculation corresponding to a total rate of 5 events/(kg day keV). The sensitivity of this analysis was however found to be limited by a surface event contamination which is currently being addressed by the Ricochet Collaboration with upgraded detectors.