LiteBIRD is a JAXA-led L-Class mission aimed at the study of B-mode polarization of the cosmic microwave background. Measurements on 15 bandwidth from 34 to 448 GHz are made on two instruments, low-frequency telescope and medium- and high-frequency telescope. To reach the desired sensitivities, more than 4500 transition edge sensors detectors, used on both instruments, will be continuously cooled to 100 mK. The cryogenic design based on shield cooling and mechanical coolers is presented in this paper. Shield cooling will be done with passive cooling and 15 K pulse tube coolers. A single cryogenic chain will cool both instruments. A 4 K stage is cooled by a 4 He Joule–Thomson cooler from Japanese Aerospace Exploration Agency, pre-cooled by Stirling coolers. Multistage adiabatic demagnetization refrigerator will be optimized to provide continuous cooling at 1.75 K, 300 mK and 100 mK with 2.2 µW of cooling power on the latter stage. Seven ADR stages provided by NASA (USA) and CEA (France) are required. Details on the thermal design, preliminary sizing and expected performance are presented.

中文翻译：

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LiteBIRD 低温链：使用机械冷却器和 ADR 进行 100 mK 冷却

LiteBIRD 是 JAXA 领导的 L 级任务，旨在研究宇宙微波背景的 B 模式极化。从 34 到 448 GHz 的 15 带宽上的测量是在两种仪器上进行的，低频望远镜和中频和高频望远镜。为了达到所需的灵敏度，两种仪器上使用的 4500 多个过渡边缘传感器检测器将持续冷却至 100 mK。本文介绍了基于屏蔽冷却和机械冷却器的低温设计。屏蔽冷却将通过被动冷却和 15 K 脉冲管冷却器完成。单个低温链将冷却两个仪器。一个 4 K 级由日本航空航天探索局的 4 He Joule-Thomson 冷却器冷却，由斯特林冷却器预冷却。多级绝热退磁制冷机将进行优化，以提供 1.75 K、300 mK 和 100 mK 的连续冷却，后级的冷却功率为 2.2 µW。需要由 NASA（美国）和 CEA（法国）提供的七个 ADR 级。提供了有关热设计、初步尺寸和预期性能的详细信息。