Transition-edge sensors with multiplexing readout for the CUPID experiment

Low-temperature calorimeters have been extensively used in the search for rare phenomena, such as neutrinoless double beta decay and dark matter. Detector sensitivity has advanced to the point that the experimental sensitivity is limited by background radioactivity. To improve the overall sensitivity of an experiment, a technique has been proposed that involves reading out the phonon and photon signals simultaneously from a scintillating or a Cherenkov light-emitting crystal. In this work, we present the development of sensitive optical-photon detectors using a novel Iridium/Platinum bilayer superconducting transition-edge-sensor (TES) on a large area dielectric wafer (Si/Ge), acting as a photon absorber. These detectors are suitable for next-generation calorimetric experiments requiring thousands of channels.

A frequency-domain multiplexing readout to readout thousands of TES bolometers will be a key to manage thermal heat load and radiation for the next generation calorimetry experiments. To that end, we adapted frequency domain multiplexing technology that was developed for TES sensors for the cosmic microwave background experiment. We designed a new resonator chip comprising ten superconducting resonators to match readout bandwidth to CUPID's (CUORE Upgrade with Particle IDentification) sensor's bandwidth, size, and noise requirements. In our setup, TES sensors are cooled to ~10 mK, and the readout resonators and SQUID (superconducting quantum interference device) amplifier are situated at a few hundred mK stage. The connection between the TESs and the resonators and SQUID is done using superconducting aluminum traces on Kapton backing. We report on the characterization of the optical photon detectors and readout performances. We will report on energy and timing resolution of the sensors as well as the implementation of the multiplexing readout in a ten-channel demonstrator.