Paul Subhradip, Bouleau Eric, Reynard-Feytis Quentin, Arnaud Jean-Pierre, Bancel Florian, Rollet Bertrand, Dalban-Moreynas Pierre, Reiter Christian, Purea Armin, Engelke Frank, Hediger Sabine, De Paëpe Gaël
Univ. Grenoble. Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
Univ. Grenoble Alpes, CEA, IRIG, DSBT, 38000 Grenoble, France.
J Magn Reson. 2023 Nov;356:107561. doi: 10.1016/j.jmr.2023.107561. Epub 2023 Sep 29.
We report here instrumental developments to achieve sustainable, cost-effective cryogenic Helium sample spinning in order to conduct dynamic nuclear polarisation (DNP) and solid-state NMR (ssNMR) at ultra-low temperatures (<30 K). More specifically, we describe an efficient closed-loop helium system composed of a powerful heat exchanger (95% efficient), a single cryocooler, and a single helium compressor to power the sample spinning and cooling. The system is integrated with a newly designed triple-channel NMR probe that minimizes thermal losses without compromising the radio frequency (RF) performance and spinning stability (±0.05%). The probe is equipped with an innovative cryogenic sample exchange system that allows swapping samples in minutes without introducing impurities in the closeloop system. We report that significant gain in sensitivity can be obtained at 30-40 K on large micro-crystalline molecules with unfavorable relaxation timescales, making them difficult or impossible to polarize at 100 K. We also report rotor-synchronized 2D experiments to demonstrate the stability of the system.
我们在此报告为实现可持续、具有成本效益的低温氦样品旋转而进行的仪器开发，以便在超低温（<30 K）下进行动态核极化（DNP）和固态核磁共振（ssNMR）。更具体地说，我们描述了一种高效的闭环氦系统，该系统由一个高效的热交换器（效率为95%）、一个单级低温制冷机和一个单级氦压缩机组成，用于驱动样品旋转和冷却。该系统与新设计的三通道核磁共振探头集成在一起，该探头在不影响射频（RF）性能和旋转稳定性（±0.05%）的情况下将热损失降至最低。该探头配备了创新的低温样品交换系统，可在几分钟内更换样品，而不会在闭环系统中引入杂质。我们报告称，对于具有不利弛豫时间尺度的大型微晶分子，在30 - 40 K时可获得显著的灵敏度提升，而这些分子在100 K时很难或无法极化。我们还报告了转子同步二维实验，以证明该系统的稳定性。
