2021-11-19 11:00  P5A-1

Challenge to temperature noise of POLARBEAR-2: From 0.3 K to 300 K

Daiki Tanabe

Observations of the cosmic microwave background (CMB) have played an essential role to establish the Big Bang cosmology and to constrain parameters of the Lambda-CDM model. POLARBEAR-2 is one of the ground-based CMB observation projects which is located in Atacama highland, Chile. It aims to precisely measure B-mode (curl) polarization pattern of the CMB in scales from sub-degree to degree angle for constraining the summation of neutrino masses and inflationary tensor-to-scalar ratio. The millimeter-waves receiver of POLARBEAR-2 deploys 7,588 superconducting detectors on a 0.3 Kelvin cold stage. Beyond just cooling the detector stage, the temperature fluctuation needs to be stabilized enough to achieve high sensitivity. Furthermore, also the room-temperature components, such as mirrors and readout electronics, have their requirements on temperature stability. In this talk, I introduce the cryogenic and readout techniques of POLARBEAR-2 focusing on non-negligible thermal effects on them.