Administrative Supplement to A high-resolution 1.3-GHz LTS/HTS NMR magnet (1.3G)

从 NMR 最简单的角度来看，较高场 (B0) 的优点是提高灵敏度和分辨率。对于 核磁共振波谱、灵敏度和分辨率分别取决于振幅和频率 测量。信号平均实验中单位时间的灵敏度和 3D 实验的分辨率 理想情况下，改进为 ω3，因此改进为 B03。因此，目前质子频率从 900 MHz 增加到 麻省理工学院-哈佛磁共振中心的最高频率达到 1.3 GHz，提高了灵敏度 分辨率提高了 3 倍。更高频率的这种好处是我们在 2000 年提出一项倡议的基础 通过结合低温和高温超导磁体，向 1 GHz NMR 磁体迈进， LTS 和 HTS； 2007 年，提议的频率增加到 1.3 GHz。 HTS 在频率上是强制性的 高于 1 GHz，因此，我们的 1.3 GHz LTS/HTS NMR 磁体 (1.3G) 结合了 500 MHz LTS NMR 磁体 (L500) 带有 800 MHz HTS 插入件 (H800)。 HTS 导体用于此 4K 应用并不是因为其高 温度能力，而是因为它们能够实现比实际更高的磁场的能力 仅通过 LTS 即可达到。尽管在设计和建造方面尽了最大努力，但“伤口”的同质性 实际上，核磁共振磁体与所需规格相差两个数量级以上。对于领域 匀场，修订后的第 3BZ 阶段的另一项关键活动是现场测绘，需要精确的探头定位 沿着优化的路径和精确的测量，从中得出目标场梯度，进而 指导适当的匀场线圈的设计，在我们的例子中，是 HTS 和室温 (RT) 的匀场线圈，两者均是 在此修订后的第 3BZ 阶段设计和建造。因为 HTS 插入物作为“大”非金属的来源而臭名昭著。 均匀场、场匀场我们的 1.3G 将具有挑战性和费力，需要创新的想法。具体的 2000 年开始的 MIT 1.3-GHz LTS/HTS NMR 磁体最后阶段的目标 (SA) 是实现两个 NMR 的重要要求。前两年，我们将： 1）更换2018年3月测试中损坏的H800 带有新的 800 MHz HTS 插入件 (H800N) 和 2) 将 L500 和 H800N 结合起来完成新的非 NMR 30.5- T L500/H800N磁铁；在过去的两年里，我们将3）转换非NMR 30.5-T场以实现高 分辨率 1.3 GHz NMR 磁体 (1.3G)。为了实现 SA3，我们将应用两项创新技术：1) HTS Z1 和 Z2 匀场线圈，安装在 H800N 的孔中； 2) 电流扫描反转和场振动以减轻 屏蔽电流场 (SCF) 是一种不均匀的反磁场，叠加在主磁场上，严重影响 会降低空间场质量，特别是对于像我们的 H800N 这样的高温超导磁体。我们还将部署铁 磁被动匀场和 RT 主动匀场，都是我们的设计。我们相信我们的1.3G将会成为 高场核磁共振以及药物发现和开发的重要力量；它将服务于整个美国核磁共振 社区将在未来几十年内对生物医学科学产生全球影响。我们也相信 我们的 1.3G 将成为高分辨率 >1-GHz NMR 磁体的模型，必须包含 HTS 插入件。

In the simplest view of NMR, the advantages of higher field (B0) are improved sensitivity and resolution. For NMR spectroscopy, sensitivity and resolution depend, respectively, on amplitude and frequency of measurement. Sensitivity per unit time in signal averaging experiments and resolution for 3D experiments both ideally improve as ω3 and, hence, B03. Thus, increased proton frequency, for example, from 900 MHz, currently the highest frequency at the MIT-Harvard Magnetic Resonance Center, to 1.3 GHz, increases sensitivity and resolution by a factor of 3. This benefit of higher frequency was the basis of our initiative in 2000 to propose a long march towards a 1-GHz NMR magnet by combining low- and high-temperature superconducting magnets, LTS and HTS; in 2007 the proposed frequency was increased to 1.3 GHz. HTS is mandatory at frequencies above 1-GHz, thus, our 1.3-GHz LTS/HTS NMR magnet (1.3G) combines a 500-MHz LTS NMR magnet (L500) with an 800-MHz HTS insert (H800). HTS conductors are used in this 4K application not for their high- temperature capabilities, but rather for their ability to achieve significantly higher magnetic field than can be reached by LTS alone. Despite the best efforts in design and construction, the homogeneity of an “as-wound” NMR magnet in reality will be more than two orders of magnitude away from required specifications. For field shimming, another critical activity in this Revised Phase 3BZ is field mapping, requiring exact probe positioning along optimized path and accurate measurement, from which to derive the target field gradients that in turn guide the design of appropriate shim coils, in our case, of HTS and room-temperature (RT), both to be designed and built in this Revised Phase 3BZ. Because HTS insert is notorious as a source of “large” non- uniform field, field shimming our 1.3G will be challenging and laborious, requiring innovative ideas. The specific aims (SA) of the last phase of this MIT 1.3-GHz LTS/HTS NMR magnet that began in 2000 are to achieve two vital requirements for NMR. In the first two years, we will: 1) replace the H800 damaged in March 2018 test with a new 800-MHz HTS insert (H800N) and 2) combine L500 and H800N to complete a new non-NMR 30.5- T L500/H800N magnet; and in the last two years we will 3) convert the non-NMR 30.5-T field to realize a high- resolution 1.3 GHz NMR magnet (1.3G). To achieve SA3, we will apply two innovative techniques: 1) HTS Z1 and Z2 shim coils, installed in the bore of H800N; and 2) current-sweep-reversal and field-shaking to mitigate the screening-current field (SCF), a non-uniform diamagnetic field, superposed on the main field that severely degrades the spatial field quality particularly for HTS magnets like our H800N. We will also deploy ferro- magnetic passive shimming and RT active shimming, both of our design. We believe that our 1.3G will become a vital force in high-field NMR as well as for drug discovery and development; it will serve the entire U.S. NMR community for decades to come and have a worldwide impact on biomedical sciences. We also believe that our 1.3G will become a model for high-resolution >1-GHz NMR magnets that must incorporate HTS inserts.