Germanium target sensed by phonon-mediated kinetic inductance detectors

Cryogenic phonon detectors are adopted in experiments searching for dark matter interactions or coherent elastic neutrino-nucleus scattering, thanks to the low energy threshold they can achieve. The phonon-mediated sensing of particle interactions in passive silicon absorbers has been demonstrated with kinetic inductance detectors (KIDs). Targets with neutron number larger than silicon, however, feature a higher cross section to neutrinos, while multi-target absorbers in the dark matter experiments would provide a stronger evidence of a possible signal. In this work, we present the design, fabrication, and operation of KIDs coupled to a germanium absorber, achieving phonon-sensing performance comparable to silicon absorbers. The device introduced in this work is a proof of concept for a scalable neutrino detector and for a multi-target dark matter experiment.