Development of the ultra-low loss superconducting resonators integrated with detectors for frequency-domain multiplexing readout of future Cosmic Microwave Background experiments

Cosmic Microwave Background (CMB) use polarization sensitive detectors to study the early universe. The number of such detectors needed for field deployed CMB experiments has been growing steadily from 1000 (stage-II) to 10,000 (stage-III) and projected stage IV experiments are to include 100,000 detectors. The Particle Physics Project Prioritization Panel (P5) outlined a strategic plan for US particle physics research over the coming decade in 2014. The panel recommended, "support CMB experiments as part of the core particle physics program. The multidisciplinary nature of the science warrants continued multiagency support." In order to reduce the thermal load on subKelvin detectors from readout circuity at higher temperature stages, a way to readout multiple detectors on the same readout line must be facilitated. HYPRES in collaboration with LBNL will develop low-loss, high frequency superconducting resonant circuits that allow for frequency domain multiplexing of many detector signals on a single readout line. Currently, LC resonators are located on a separate circuit board and connected via cable to the CMB detectors. This arrangement increases bulk and thermal loading and is not feasible for the larger number of detectors envisioned in future experiments. Our design, in contrast, will integrate superconducting resonators directly on the same wafer as the detectors and allow both to be fabricated in the same process flow. This project will pave the way for full integration of detectors, resonators, and readout circuitry. The primary goal of this program is the development of cryogenic bolometer array technology for future Cosmic Microwave Background experiments. In doing so the project will focus on developing integrated LC resonators for multiplexed detector readout. The use of LC resonators in circuits is ubiquitous, including in frequency modulation as envisioned here, but also in impedance matching, signal processing (filtering, tuning and mixing), and amplifiers. The expertise gained by HYPRES in fabricating superconducting resonators and integrating them with other components on the same wafer will enhance their offerings to both government and commercial customers who rely on HYPRES’ custom superconducting fabrication capabilities.