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

项目摘要 TR&D 4建议建造一个低温再循环系统和一个相关的MAS探头， 允许使用He气体作为流体在200-250 kHz范围内进行高旋转频率MAS实验。此外，本发明还提供了一种方法， 该系统将在低温下工作，使得DNP实验具有改进的灵敏度。低温 系统将包括以下4个步骤： (1)我们计划设计和建造一个再循环系统，在80 K下进行MAS实验， 最初使用N2作为工作流体，因为它更便宜，并且允许我们组装和调试系统 - 确保不泄漏等。 (2)在第二步中，我们将He引入系统作为工作流体。在环境温度下 这将提供一种实现高自旋频率的方法，最终的目标是200-250 kHz 政权因此，该系统将在执行TR&D 1、2和4中的实验以及几乎所有的实验中发挥重要作用。 DBP和CE中的所有固态NMR实验。 (3)一旦这是功能，我们计划使用他在~20-50 K，这将提供另一个因素2-4英寸 玻尔兹曼极化用于常规NMR和DNP实验。它还可以使1H检测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， 在500 MHz上成功实现了两次。 同时，我们计划开发一种新的MAS转子制造的单晶金刚石。 金刚石是优选的材料，因为其高强度、优异的导热性，并且它是 对微波是透明的，因此它将改进DNP增强。因为转子很小， 经济上可行。转子将可能是激光加工的单晶与飞秒激光 如果我们成功地在100 K下以100 kHz以上的频率旋转，它们将打开一个全新的1H检测领域 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.