Speaker
Description
Continued advancements in sub-eV calorimetric measurements are being enabled through the athermal phonon detection channel, with applications spanning a diverse array of fields, including low-mass dark matter searches, coherent elastic neutrino-nucleus scattering, and quantum information science. While Transition Edge Sensors (TESs) have achieved the lowest thresholds to date, they face significant scalability bottlenecks due to the inherent constraints of conventional SQUID readout architectures. To address this limitation, we present an update on R&D to develop a practical, highly multiplexed, microwave multiplexer for athermal phonon TESs which can enable a dramatic increase in both sensor count and target mass, with a focus on sub-GeV dark matter searches as a target application. This work leverages advances from highly scaled mm-wave, x-ray, and gamma-ray TES systems, adapting them to the unique needs of low-threshold rare event measurements. We present a preliminary proof of concept multiplexed readout of background pulses, show measurements of acceptably low parasitic readout loading, and discuss designs and challenges for a next-generation athermal phonon detector at scale.