Design Overview of the MIT 1.3-GHz LTS/HTS NMR Magnet with a New REBCO Insert

We present a design overview of the MIT 1.3-GHz LTS/HTS NMR magnet (1.3G) with a newly designed 835-MHz REBCO insert (H835) as a replacement of the 800-MHz REBCO insert that was damaged when it quenched during operation in 2018. The new H835 contributes 19.6 T as designed, with an LTS back-ground magnet of 10.9 T, toward a total field of 30.5 T that corre-sponds to a proton resonance frequency of 1.3 GHz. The H835 is de-signed to be stable within 1.3G design constraints. The design also prevents the entire insert from permanent damage in the improba-ble event like a quench. Key design features are: 1) a single-solenoid structure, composed of 38 stacked metal-co-wound no-insula-tion and 4 stacked no-insulation double-pancake coils with mechan-ically improved cross-over sections; 2) enhanced thermal stability; and 3) reduced excessive current margin with a detect-and-activate-the-heater method. This paper includes: 1) electromagnetic and me-chanical design of the H835; 2) cryogenics overview; 3) quench pro-tection schemes; and 3) discussion on the next steps toward the 1.3G.本研究介绍了麻省理工学院（MIT）1.3 GHz低温超导（LTS）/高温超导（HTS）核磁共振（NMR）磁体（简称1.3G装置）的设计概况。该装置以新设计的835 MHz稀土钡铜氧化物（REBCO）插入式磁体（H835），替代了2018年运行期间因失超损坏的800 MHz REBCO插入式磁体。这款全新的H835设计可提供19.6特斯拉（T）的磁场强度，搭配10.9 T的LTS背景磁体，最终总磁场可达30.5 T，对应质子共振频率为1.3 GHz。H835的设计满足1.3G装置的各项约束要求，具备优异稳定性；即便发生极低概率的失超事件，该设计也可避免整个插入式磁体遭受永久性损坏。其核心设计特征包括：1） 单螺线管结构，由38层堆叠式金属共绕无绝缘线圈与4层堆叠式无绝缘双饼线圈组成，且过渡段的机械性能得到优化；2） 提升热稳定性；3） 通过"检测-触发加热器"方法降低冗余电流裕度。本文涵盖以下内容：1） H835的电磁与机械设计；2） 低温系统概况；3） 失超保护方案；3） 针对1.3G装置后续研发步骤的讨论。