We describe an on-sky demonstration of a microwave-multiplexing readout system in one of the receivers of the Keck Array, a polarimetry experiment observing the cosmic microwave background at the South Pole. During the austral summer of 2018–2019, we replaced the time-division multiplexing readout system with microwave-multiplexing components including superconducting microwave resonators coupled to radio frequency superconducting quantum interference devices at the sub-Kelvin focal plane, coaxial-cable plumbing and amplification between room temperature and the cold stages, and a SLAC Microresonator Radio Frequency system for the warm electronics. In the range 5–6 GHz, a single coaxial cable reads out 528 channels. The readout system is coupled to transition-edge sensors, which are in turn coupled to 150-GHz slot-dipole phased-array antennas. Observations began in April 2019, and we report here on an initial characterization of the system performance.
Bibliographical noteFunding Information:
This work was supported by the US Department of Energy, Office of Science, Contract DE-AC02-76SF00515. CY was supported by the NSF GRFP.
This work was supported by the US Department of Energy, Office of Science, Contract DE-AC02-76SF00515. CY was supported by the NSF GRFP. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
- Keck Array
- Microwave multiplexing
- Tone tracking