Half-meter Scale Superconducting Magnetic Bearing for Cosmic Microwave Background Polarization Experiments
Half-meter Scale Superconducting Magnetic Bearing for Cosmic Microwave Background Polarization Experiments
复制标题
DOI：
10.1088/1742-6596/1590/1/012060
复制
发表时间：
2020-07
期刊：
影响因子：
--
通讯作者：
Y. Sakurai;P. Ashton;A. Kusaka;C. Hill;K. Kiuchi;N. Katayama;O. Tajima
中科院分区：
文献类型：
--
作者：
Y. Sakurai;P. Ashton;A. Kusaka;C. Hill;K. Kiuchi;N. Katayama;O. Tajima
报道了一种用于连续旋转低温半波片偏振调制器的大直径超导磁轴承的研制。对CMB偏振的精确测量将对宇宙膨胀施加更严格的约束，描述早期宇宙的快速膨胀。偏振调制器是抑制1/f污染的关键仪器，1/f污染主要由大气噪声引起，并且用于减轻差分正交偏振检测器时出现的系统不确定性。为了确保足够的视场并减少热辐射，偏振调制器必须具有> 500 mm的通光孔径直径，并且必须在低温下工作。我们建造了一个超导磁轴承（SMB）的内径为550毫米，这是迄今为止在任何CMB极化实验中使用的最大。我们在液氮温度下测试了轴承的摩擦力和刚度。测得的总损耗为0.4 W，弹簧常数>105 N/m，满足典型的实验要求。此外，我们通过改变盘形YBCO瓦片的数量进行了性能测试，然后确认SMB性能与YBCO体积成正比。
We report the development of a large-diameter superconducting magnetic bearing (SMB) used in a continuously rotating cryogenic half-wave plate (HWP) polarization modulator for cosmic microwave background (CMB) polarization experiments. A precise measurement of the CMB polarization will place tighter constrains on cosmic inflation, describing the rapid expansion of the early universe. The polarization modulator is a critical instrument for suppressing 1/f contamination, which is mainly caused by atmospheric noise, and for mitigating systematic uncertainties that arise when differencing orthogonal polarization detectors. To ensure a sufficient field of view and to reduce thermal emission, the polarization modulator must have a clear-aperture diameter of > 500 mm and must operate at cryogenic temperatures. We constructed a superconducting magnetic bearing (SMB) with an inner diameter of 550 mm, which is the largest used in any CMB polarization experiment to date. We tested the friction and stiffness of the bearing at liquid nitrogen temperatures. The measured total loss is 0.4 W and the spring constant is >105 N/m, which satisfies typical experimental requirements. Furthermore, we performed a performance test by changing the number of disk-shaped YBCO tiles, and then confirmed that the SMB performance was proportional to the YBCO volume.