Large-area photon calorimeter with Ir-Pt bilayer transition-edge sensor for the CUPID experiment

CUPID is a next-generation neutrinoless double-β decay experiment that will require cryogenic light detectors to improve background suppression, via the simultaneous readout of heat and light channels from its scintillating crystals. In this work, we showcase light detectors based on an alternative Ir-Pt bilayer transition-edge sensor. We have performed a systematic study to improve the thermal coupling between the photon absorber and the sensor, and thereby its responsivity. Our first devices meet CUPID’s baseline noise requirement of < 100 eV rms. Our detectors have risetimes of approximately 180 μs and measured timing jitter of < 20 μs for the expected signal to noise at the Q value of the decay, which achieves the CUPID’s criterion of rejecting two-neutrino double-β decay pile-up events. The current work will inform the fabrication of future devices, culminating in the final TES design and a scaleable readout scheme for CUPID.