Transforming cryogenic optics for cosmic microwave background experiments

Future experiments mapping the cosmic microwave background (CMB) are designed to revolutionize our understanding of the infant universe, the standard model of particle physics, structure formation, and the nature of dark matter. A key effort involves constraining or detecting the energy scale of cosmic inflation. A detection would mark a watershed moment in cosmology and high-energy physics, but in order to push constraints significantly past current limits, we need a dramatic change in instrument characterization capabilities — the primary focus of CMBeam.To address this challenge, we propose to construct a novel cryogenic holography facility for the purposes of testing optical systems of current and future experiments observing at microwave frequencies (40–400 GHz). We will use this facility to develop never-before-seen optical measurements that are critical for the success of next-generation experiments studying the CMB. As part of this program, we will perform warm and cryogenic (4-Kelvin) holography measurements of a complete reimaging optics tube for the Simons Observatory Large Aperture Telescope, the flagship CMB experiment of this decade. In a complementary effort, we will lead an ambitious analysis and calibration program for the Simons Observatory, which will deploy 60,000 cryogenically cooled detectors — three times the number of currently fielded detectors globally — in a site located 5,200 m above sea level in the Atacama Desert, Chile. Finally, we will develop algorithms that enable the design of novel freeform (asymmetric) optical systems that can greatly extend the scientific reach of future large-aperture telescopes such as upgraded version of the Simons Observatory and the CMB-S4 experiment.