Speaker
Description
The development of low-threshold detectors for the study of coherent elastic neutrino-nucleus scattering and for the search for light dark matter calls for new calibration methods at sub-keV energies. We suggest this can be provided by the nuclear recoils resulting from the gamma emission following thermal neutron capture [1]. In particular, several MeV-scale single-gamma transitions induce well-defined nuclear recoil peaks in the 100 eV – 1 keV range.
Using the FIFRELIN code initially designed to study fission fragment de-excitation [2], complete schemes of gamma-cascades for various isotopes can be predicted with high accuracy to determine the continuous background of nuclear recoils below the calibration peaks. The FIFRELIN high precision is achieved because the nucleus level scheme is built based on available nuclear structure information and completed if necessary with nuclear models to take into account missing information. First validations of the FIFRELIN high accuracy performed in the framework of STEREO experiment for gadolinium isotopes and with a laboratory neutron source for tungsten isotopes will be shown.
We present also a comprehensive experimental concept for the calibration of CaWO4 [3] and Ge cryogenic detectors at a research reactor emphasizing the importance of nuclear physics in this study. For CaWO4 the simulations show that two nuclear recoil peaks at 112.5 eV and 160.3 eV should be visible above background simply in the spectrum of the cryogenic detector. Then we discuss how the additional tagging for the associated gamma increases the sensitivity of the method and extends its application to a wider energy range and to other cryogenic detector materials such Ge or Si or Al.
[1] L. Thulliez, D. Lhuillier et al., Calibration of nuclear recoils at the 100 eV scale using neutron capture, Journal of Instrumentation, 16, 7 (2021)
[2] O. Litaize et al., Fission modelling with FIFRELIN, European Physical Journal A, 51, 12 (2015)
[3] G. Angloher et al. Results on MeV-scale dark matter from a gram-scale cryogenic calorimeter operated above ground: CRESST Collaboration, European Physical Journal C, 77:637, 9 2017
