Park Dongkeun, Bascuñán Juan, Michael Philip C, Lee Jiho, Hahn Seungyong, Iwasa Yukikazu
Francis Bitter Magnet Laboratory/Plasma Science and Fusion Center, MIT, Cambridge, MA 02139 USA.
Department of Electrical and Computer Engineering, Seoul National University, Seoul, 08826, South Korea.
IEEE Trans Appl Supercond. 2018 Apr;28(3). doi: 10.1109/TASC.2017.2780043. Epub 2017 Dec 4.
We present construction and test results of Coils 2 and 3 of a 3-coil 800-MHz REBCO insert (H800) for the MIT 1.3 GHz LTS/HTS NMR magnet currently under construction. Each of three H800 coils (Coils 1-3) is a stack of no-insulation REBCO double pancakes (DPs). The innermost 8.67-T Coil 1 (26 DPs) was completed in 2016; the middle 5.64-T Coil 2 (32 DPs) has been wound, assembled, and tested; and for the outermost 4.44-T Coil 3, its 38 DPs have been wound and preliminary tests were performed to characterize each DP at 77 K. Included for Coil 2 are: 1) 77-K data of critical current, index, and turn-to-turn characteristic resistivity of each DP; 2) stacking order of the 32 DPs optimized to maximize the Coil 2 current margin and minimize its Joule dissipation in the pancake-to-pancake joints; 3) procedure to experimentally determine and apply a room-temperature preload to the DP stack; 4) 77-K and 4.2-K test results after each of 64 pancakes was over-banded with 75-μm-thick stainless steel tape for a radial thickness of 5 mm. Presented for each DP in Coil 3 are 77-K dada of critical current, index, and turn-to-turn characteristic resistivity.
我们展示了正在建造的麻省理工学院1.3 GHz LTS/HTS NMR磁体的三线圈800 MHz REBCO插入件（H800）中线圈2和线圈3的建造及测试结果。三个H800线圈（线圈1 - 3）中的每一个都是无绝缘REBCO双饼（DP）堆叠而成。最里面的8.67 T线圈1（26个DP）于2016年完成；中间的5.64 T线圈2（32个DP）已绕制、组装并测试；对于最外面的4.44 T线圈3，其38个DP已绕制完成，并在77 K下对每个DP进行了初步测试以表征其特性。线圈2包含以下内容：1）每个DP在77 K时的临界电流、指数和匝间特征电阻率数据；2）32个DP的堆叠顺序，该顺序经过优化以最大化线圈2的电流裕度并最小化其在饼间接头处的焦耳耗散；3）实验确定并对DP堆叠施加室温预载的程序；4）在64个饼中的每一个都用75μm厚的不锈钢带进行径向厚度为5 mm的过带处理后的77 K和4.2 K测试结果。给出了线圈3中每个DP在77 K时的临界电流、指数和匝间特征电阻率数据。
