Speaker
Description
The scalability of sub-Kelvin superconducting sensors is generally limited by their associated superconducting readout electronics, motivating multiplexing schemes which reduce the system complexity, cost, and thermal load on the refrigerator. Microwave SQUID multiplexing, which naturally has access to ~100x the operation bandwidth of alternative schemes, is a compelling candidate for future advanced readout. It combines the inherent frequency-division multiplexing capability of kinetic inductance detectors with the ability to independently optimize the sensor array, enabling broad compatibility with a variety of TES and MMC sensors. Here, we report on two directions of technology development advancing microwave SQUID readout for HEP applications.
First, we summarize a demonstration of the largest TES multiplexing factor to date, implemented with TES bolometers suitable for mm-wave observatories probing inflationary physics and constraining light relics via the cosmic microwave background. By doubling the bandwidth of previous implementations, this development increases the multiplexing factor from 910 to 1,820. We further show that the channel yield, electrical crosstalk, and readout noise are consistent with the needs of ground-based cosmic microwave background telescopes.
Second, we describe new work to develop a microwave SQUID multiplexer for sub-eV threshold TES calorimeters suitable for direct detection searches for keV - GeV mass dark matter. A unique challenge with any readout scheme of such sensors is the avoidance of sub-fW parasitic power dissipated in the TESs, which can saturate them. We report on efforts to model, measure, and mitigate the sources of parasitic leakage in microwave SQUID readout as a first step to developing a scaling path towards a future experiment with thousands of TES sensors.
