The \(\nu \) -cleus experiment: a gram-scale fiducial-volume cryogenic detector for the first detection of coherent neutrino–nucleus scattering

We discuss a small-scale experiment, called \(\nu \)-cleus, for the first detection of coherent neutrino–nucleus scattering by probing nuclear-recoil energies down to the 10 eV regime. The detector consists of low-threshold CaWO\(_4\) and Al\(_2\)O\(_3\) calorimeter arrays with a total mass of about 10 g and several cryogenic veto detectors operated at millikelvin temperatures. Realizing a fiducial volume and a multi-element target, the detector enables active discrimination of \(\gamma \), neutron and surface backgrounds. A first prototype Al\(_2\)O\(_3\) device, operated above ground in a setup without shielding, has achieved an energy threshold of \({\sim }20\) eV and further improvements are in reach. A sensitivity study for the detection of coherent neutrino scattering at nuclear power plants shows a unique discovery potential (5\(\sigma \)) within a measuring time of \({\lesssim }2\) weeks. Furthermore, a site at a thermal research reactor and the use of a radioactive neutrino source are investigated. With this technology, real-time monitoring of nuclear power plants is feasible.