Cryogenic Optics and Detectors for Next-Generation Microwave Cosmology and Astrophysics Observatories

Abstract

Millimeter and sub-millimeter observatories provide a unique and powerful window into the origins, content, and evolution of the universe. In our current era of precision cosmology, measurements of the cosmic microwave background (CMB) yield constraints on frontier physics such as dark energy, the sum of the neutrino masses, and models of inflation. Measurements of the CMB also reveal the astrophysics of galaxy clusters and can then be used to glean information about the early universe. The early universe can also be studied with millimeter-wave observations of redshifted spectral line emissions from early star-forming galaxies during the Epoch of Reionization (EoR). A relatively new method, called spectral line intensity mapping (LIM), can be used to tomographically map the EoR. LIM observations of the EoR will reveal properties of the reionization sources and how reionization impacted the evolution of the intergalactic medium (IGM) into the large-scale structure we see today. In order to improve CMB observations and enable new LIM measurements, microwave observatories require high-throughput cryogenic optics and interferometry, and ultra-sensitive superconducting detectors. This dissertation presents developments of these technologies for three projects: the Atacama Cosmology Telescope (ACT), the CCAT-prime Observatory, and the Simons Observatory (SO). We begin with a presentation of in-situ warm spillover beam measurements of the Advanced ACT receiver, which have been used to improve the optical designs of future telescopes. We then discuss the design, models, and fabrication development of metamaterial-based, silicon-substrate, Fabry-Perot interferometers for CCAT-prime's [CII] LIM instrument. We then describe the characterization of prototype superconducting transition edge sensors (TES) for Simons Observatory including, critical temperature, saturation power, time constant, and complex impedance measurements. The dissertation concludes with a brief discussion of the cosmology and astrophysics science goals that these technologies will enable when they are deployed on microwave telescopes in the coming years.