Development of a contact-less cryogenic rotation mechanism employed for a polarization modulator unit in cosmic microwave background polarization experiments
Development of a contact-less cryogenic rotation mechanism employed for a polarization modulator unit in cosmic microwave background polarization experiments
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宇宙微波背景偏振实验中偏振调制器单元非接触式低温旋转机构的开发
DOI：
10.1088/1742-6596/1293/1/012083
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Hisashi Enokida
中科院分区：
文献类型：
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作者：
Yuki Sakurai;Tomotake Matsumura;Nobuhiko Katayama;Teruhito Iida;Kunimoto Komatsu;Hajime Sugai;Hiroyuki Ohsaki;Yutaka Terao;Yukimasa Hirota;Hisashi Enokida
介绍了一种用于宇宙微波背景(CMB)实验的非接触低温旋转机构的设计和性能。对中观天体偏振的精确测量有可能验证宇宙膨胀理论，该理论描述了早期宇宙的最开始(10−38秒)。偏振调制器是实验中的关键仪器之一，它是在望远镜口径处连续旋转半个波片的偏振调制器。为了减少噪声和系统不确定性，偏振调制器需要在低于20K的低温环境中以最小的散热稳定旋转，因此，我们采用了完全无接触轴承和电机相结合的旋转机构，超导磁轴承和空心孔同步电机。通过避免物理接触，可以将摩擦引起的散热和负载扭矩降至最低。我们搭建了旋转机构的样机，并进行了机械性能和热性能测试。在低温下进行了连续回转试验，证实了回转频率在0.5~3.0 Hz时，回转稳定性小于1%。并进行了热性能试验，得到了9.0 MW转子的散热量。我们讨论了使用改进的磁场均匀度的改进的磁路来减少散热。
We present the design and the performance of a contact-less cryogenic rotation mechanism used in cosmic microwave background (CMB) experiments. A precise measurement of the CMB polarization is possible to verify the cosmic inflation theory that describes the very beginning (10− 38 seconds) of the early universe. The polarization modulator, that rotates a half wave plate continuously at the aperture of the telescope, is one of the key instruments in the experiments. In order to reduce noise and systematic uncertainties, the polarization modulator is required a stable rotation with minimal heat dissipation in a cryogenic environment less than 20 K. Thus, we adopted the rotation mechanism that combines completely contact-less bearing and motor, a superconducting magnetic bearing, and a hollow bore synchronous motor. The heat dissipation and the load torque due to the friction can be minimized by avoiding physical contacts. We constructed the prototype of the rotation mechanism and carried out mechanical and thermal performance tests. A continuous rotation test in cryogenic temperature is performed, and it is confirmed that the rotation stability is less than 1% with the rotation frequency between 0.5 Hz and 3.0 Hz. We also conducted a thermal performance test, and obtained the heat dissipation at the rotor of 9.0 mW. We discussed the reduction of heat dissipation using a developed magnetic circuit with improved magnetic field uniformity.