CRYOGENIC BORE UPGRADE FOR 6T MAGNET

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 ACERT目前拥有一个牛津6 T磁体，自2002年完成初始仪器配置以来，该磁体一直与我们的95 GHz连续波/脉冲光谱仪一起使用。这种磁体具有良好的均匀性和低的制冷剂消耗，但如所提供的，具有两个主要缺点相对较窄的50 mm孔和有限的允许刀片温度范围约为-10 <$C至+60 <$C。窄膛排除了真空杜瓦瓶用于ESR波谱分析，由于其铜插入壁和氯丁橡胶“O”形环端密封，无保护膛温度范围限制。这种类型的密封件在低于约-30 ℃的温度下硬化和收缩，这不可避免地导致真空泄漏和磁体失超。我们的愿望，升级了95 GHz的光谱仪实验控制能力的新实验，如鹿3-和4-脉冲和DQC距离测量是在低温下运行这些实验。虽然我们目前正在准备一种新的无冷冻剂的9 T磁体（Cryogenic，Ltd.）为了与光谱仪一起使用，在测试和微调仪器实验能力的初始阶段，我们更愿意通过继续使用牛津6 T磁体设置来加快开发并避免引入异常。因此，我们为Oxford磁体设计并构建了一个具有低温能力的受控温度插入件（参考子项目0162），并使用定制的低温额定内部杜瓦瓶端密封件（Creavey Seal Co.）和不锈钢孔管，以承受孔温度低至至少77 K。在这次重建工作之后，我们已经在样品和孔管温度低至80 K的情况下运行CTI，而不会产生任何磁体真空问题。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ACERT currently possesses an Oxford 6T magnet that has been in use with our 95GHz cw/pulse spectrometer since completion of the initial instrument configuration in 2002. This magnet exhibits good homogeneity and low cryogen consumption but, as supplied, has two major drawbacksa relatively narrow 50mm bore and limited allowable insert temperature range of approximately -10¿ C to +60¿ C. The narrow bore precludes the use of a vacuum dewar for ESR spectroscopy, with the unprotected bore temperature range limitation due to its copper insert wall and neoprene "o"-ring end seals. This type of seal hardens and contracts at temperatures below approximately -30¿ C, effects which inevitably cause vacuum leakage and quench of the magnet. Our desire, having upgraded the 95GHz spectrometer experimental control capabilities for new experiments such as DEER 3- and 4-pulse and DQC distance measurements is to run these experiments at cryogenic temperatures. Although we are currently preparing a new cryogen-free 9T magnet (Cryogenic, Ltd.) for use with the spectrometer, during the initial phase of testing and fine-tuning the instrument experimental capabilities we prefer to expedite development and avoid introducing anomalies by continuing with the Oxford 6T magnet setup. Therefore, we designed and constructed a cryogenic-capable Controlled Temperature Insert (ref. Subproject 0162) for the Oxford magnet and rebuilt the magnet with custom cryo-rated internal dewar end seals (Creavey Seal Co.) and stainless-steel bore pipe to withstand bore temperatures down to at least 77K. Following this rebuild effort, we have operated the CTI at sample and bore pipe temperatures down to 80K without incurring any magnet vacuum problems.