Thermal analysis of a prototype cryogenic polarization modulator for use in a space-borne CMB polarization experiment

[摘要] We report a thermal analysis of a polarization modulator unit (PMU) for use in a space-borne cosmic microwave background (CMB) project. A measurement of the CMB polarization allows us to probe the physics of early universe, and that is the best method to test the cosmic inflation experimentally. One of the key instruments for this science is to use a halfwave plate (HWP) based polarization modulator. The HWP is required to rotate continuously at about 1 Hz below 10 K to minimize its own thermal emission to a detector system. The rotating HWP system at the cryogenic environment can be realized by using a superconducting magnetic bearing (SMB) without significant heat dissipation by mechanical friction. While the SMB achieves the smooth rotation due to the contactless bearing, an estimation of a levitating HWP temperature becomes a challenge. We manufactured a one-eighth scale prototype model of PMU and built a thermal model. We verified our thermal model with the experimental data. We forecasted the projected thermal performance of PMU for a full-scale model based on the thermal model. From this analysis, we discuss the design requirement toward constructing the full-scale model for use in a space environment such as a future CMB satellite mission, LiteBIRD.

[发布机构] PTI CO., LTD., 5-16-401, Kusunoki-cho, Nishi-ku, Yokohama; 220-0003, Japan^1;Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo Institute for Advanced Study (UTIAS), University of Tokyo, 5-1-5 Kashiwanoha, Chiba, Kashiwa; 277-8583, Japan^2;Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo, Kanagawa, Sagamihara; 252-5210, Japan^3;Department of Advanced Energy Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Chiba, Kashiwa; 277-8561, Japan^4;Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki; 305-0801, Japan^5

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Contactless bearings;Cosmic microwave backgrounds;Cryogenic environment;Full-scale modeling;Mechanical friction;Polarization modulators;Superconducting magnetic bearings;Thermal Performance