11:30 am–12:00 pm
ERC 401 Development of Cryogenic Infrared Filters for SPT-3G+: A New Camera to Measure the Cosmic Microwave Background Modern cosmology relies on high-precision measurements of the cosmic microwave background (CMB) to investigate fundamental questions about the universe's origin, structure, and fate. One of the leading instruments in this effort is the South Pole Telescope (SPT), which is designed to measure the CMB and has been equipped with a series of increasingly sensitive cameras, including the current SPT-3G camera and the upcoming SPT-3G+ camera. These cameras cool detectors to sub-Kelvin temperatures in a cryostat in order to reduce thermal noise and improve overall detector sensitivity. To achieve these temperatures, cryostats need a series of optical and infrared (IR) filters that reduce the radiative loading on the cryogenic stages but are still transparent to the microwave CMB photons. This work aims to develop and test these cryogenic filters for the SPT-3G+ camera using the SPT-SZ cryostat as a testbed. Diagnostic testing verified that the system can reliably reach a base temperature of 4 K. A Lake Shore 240 thermometry system was integrated into the cryostat, silicon diode thermometers were mapped and tested, and additional diode sensors were prepared for monitoring the optics tube’s thermal gradients. After assembling and characterizing the filter stack of the optics tube with several cooldowns, it will be deployed to the South Pole and installed in the SPT-3G+ receiver. Our work fills a critical gap in experimental cosmology, as this telescope has a much denser array of detectors that observe and resolve smaller spatial scales, thereby improving gravitational lensing mapping to distinguish B-modes caused by primordial gravitational waves from E-modes due to foreground matter lensing. Advisor: Brad Benson
May
22
