Phonon-Mediated KIDs as Light Detectors for Rare-Event Search: The CALDER Project

Abstract

Background suppression plays a crucial role in experiments searching for rare events, like neutrino-less double beta decay (0 $$\nu $$ DBD) and dark matter. Large mass bolometers that are among the most competitive devices in this field would largely benefit from the development of ultrasensitive light detectors, as the combined readout of the bolometric and light signals enables the particle identification. The CALDER collaboration is developing cryogenic light detectors that will match the requirements of next generation experiments: noise lower than 20 eV RMS, large active area (several cm $$^{2}$$ ), wide temperature range of operation, and ease in fabricating and operating a thousand of detectors. For this purpose, we are exploiting the excellent energy resolution and the natural multiplexed read-out provided by kinetic inductance detectors (KIDs). These devices can be operated in a phonon-mediated approach, in which KIDs are coupled to a large insulating substrate in order to increase the active surface from a few mm $$^{2}$$ to 25 cm $$^{2}$$ . Our current best prototype, based on aluminum LEKIDs, reached a baseline sensitivity of 80 eV with an overall efficiency of about 20 %.