Development of the Ultra-Low Loss Superconducting Resonators Integrated with Detectors for Frequency-Domain Multiplexing Readout of Future Cosmic Microwave Background Experiments

Superconducting transition edge sensors are a key technology for measuring the Cosmic Microwave Background radiation leftover from the early universe. To reach the large number of sensors (~400,000-500,000) needed for next generation experiments, solutions must be found to reduce time, weight, size, and cost of the sensor arrays. This project addresses these issues by both integrating the sensors with peripheral circuitry to reduce the overall size, and also by exploiting the increased production volume and reliability of a commercial foundry for detector fabrication. In Phase 1, superconducting resonators that enable the readout of several detectors on a single measurement channel were successful fabricated on the same wafers as the detectors, thus eliminating the need for external multiplexing circuitry. In addition, nearly all detector fabrication steps were successfully carried out at the commercial foundry. In Phase II, the remaining fabrication steps will be brought to the commercial foundry so that there is a complete commercial end-to-end process. Production will be improved iteratively over the Phase II period to maximize detector performance, yield, and production volume. Commercial Applications and Other Benefits: This work will result in a commercial source of superconducting sensor arrays for the government, academic, and industrial sectors. The specific sensors being developed have application in Cosmic Microwave Background and light dark matter experiments. The integrated resonator technology is useful for multiplexed readout and control of sensors as well as other array based elements, such as qubits for quantum information processing.