TR&D 4 -- Advanced Magic Angle Spinning NMR methods

项目摘要 R&D 4计划建造一个低温再循环系统和一个相关的MAS探测器，将 允许在200-250千赫范围内使用氦气作为流体进行高自旋频率的MAS实验。此外, 该系统将在低温下工作，使DNP实验具有更高的灵敏度。深冷技术 系统将包括以下4个步骤： (1)我们计划设计和建造一个循环系统，在80K下进行MAS实验， 最初使用氮气作为工作液，因为它价格较低，并将允许我们组装和调试系统 -确保不会泄漏等。 (2)在第二步中，我们将把氦气作为工作液引入系统。在环境温度下 这将提供一种实现高旋转频率的方法，最终目标是200-250 khz 政权。因此，该系统将在研发1、2和4以及今后几年内进行重要的实验 在DBP和CE中进行的所有固体核磁共振实验。 (3)一旦工作正常，我们计划在~20-50K下使用He，这将提供另一个2-4英寸的系数 常规核磁共振和DNP实验的玻尔兹曼极化。它还可以使1H检测到DNP 实验。 (4)将根据我们的传输线设计，构建用于低温操作的MAS探头 已经在500 MHz频率下成功实现了两次。 同时，我们计划开发一种由单晶金刚石制成的新型MAS转子。 钻石是首选的材料，因为它的高强度，良好的导热性，它是 对微波透明，因此它将改善DNP增强。因为转子很小，所以这是 在经济上是可行的。转子可能会用飞秒激光从单晶激光加工而成。 如果我们成功地在100K下以100千赫以上的频率旋转，他们将打开一个全新的1H探测到的领域 DNP。

Project Summary TR&D 4 proposes to construct a cryogenic recirculation system and an associated MAS probe that will permit high spinning frequency MAS experiments using He gas as a fluid in the 200-250 kHz regime. In addition, the system will function at low temperatures enabling DNP experiments with improved sensitivity. The cryogenic system will involve 4 steps as follows: (1) We plan to design and construct a recirculation system to perform MAS experiments at 80 K that will initially use N2 as a working fluid since it is less expensive and will allow us to assemble and debug the system – insure that does not leak, etc. (2) In the second step we will introduce He into the system as the operating fluid. At ambient temperatures this will provide a means to achieve high spinning frequencies, with the eventual goal being the 200-250 kHz regime. Therefore, this system will be important in performing the experiments in TR&D 1, 2 and 4 and for almost all of the solid state NMR experiments in the DBP’s and CE’s. (3) Once this is functioning we plan to use He at ~20-50 K which will provide another factor of 2-4 in Boltzmann polarization for both conventional NMR and DNP experiments. It could also enable 1H detected DNP experiments. (4) Will construct a MAS probe for low temperature operation based on our transmission line design that has been successfully implemented twice at 500 MHz. Concurrently we plan to develop a new class of MAS rotors fabricated from single crystal diamond. Diamond is the preferred material because of its high strength, excellent thermal conductivity, and it is transparent to microwaves so that it will improve DNP enhancements. Because the rotors are small this is economically feasible. The rotors will probably be laser machined from single crystals with a femtosecond laser and if we are successful in spinning at above 100 kHz at 100 K they will open an entire new field of 1H detected DNP.