DEVELOPMENT OF 750MHZ SUPERCONDUCTING PROBE

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。超导核磁共振探针包含由超导材料制成的冷却射频线圈，从而改善了实验的信噪比。这些在500和600 MHZ的商用探头，Core 3的目标是与NHMFL和Bruker Instruments的同事合作，构建改进的750MHz探头。2003年春，我们将目标改为使用单轴脉冲场梯度的600 MHz 1 mm HCN探头。Withers已经建立了安装硬件和13C和2H线圈。他们现在正在构建1H和15N线圈，他们最初的尝试导致1H线圈共振频率比预期高5%。他们测试的那批线圈都有异常低的Q值，他们现在确信线圈是由一批坏的YBCO超导薄膜制成的。更多的超导晶圆即将问世，在NHMFL博士后Saikat Saha的帮助下，我们在建模和更好地理解高温超导谐振器的行为方面也取得了真正的进展。似乎有了这种改进的理解，我们可以提高我们设计新频率和尺寸要求的能力，但我们也可以改善谐振器的电流处理和射频均匀性。Saha博士一直在使用矩量法（MoM）仿真软件包（来自Zeland Software的IE3D）来模拟高温超导线圈设计中的共振频率和电流分布。对于平面线圈来说，MoM方法更快、更实用，因为平面线圈必须被细分成数百个准二维单元。它只处理平面介质，但也可能包括在低温探针中使用的圆柱形屏蔽。我们预计在明年测试一个工作探测器。如果这有效，这个1毫米高温超导探头将具有最高的每体积S/N在任何探头迄今为止建成。

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. Superconducting NMR probes contain cooled rf coils made of superconducting material that result in improved signal to noise for the experiment. These are commercially available at 500 and 600 MHZ and the goal in Core 3 is to construct improved probes at 750MHz in collaboration with colleagues at the NHMFL and Bruker Instruments. In the spring of 2003, we changed our goal to a 600 MHz 1 mm HCN probe with a single-axis pulsed field gradient. Withers has already built the mounting hardware and 13C and 2H coils. They are now building the 1H and 15N coils, and their initial attempt lead to a 1H coil which resonated ~5% in frequency than expected. The batch of coils they tested all had unusually low Q values, and they now are convinced that coils were made from a bad batch of YBCO superconducting film. More superconducting wafers will be coming soon, and with the help of Saikat Saha, a postdoctoral associate at the NHMFL, we are also making real progress in modeling and better understanding the behavior of the HTS resonators. It appears that with this improved understanding we can improve our ability to design for new frequency and size requirements, but we may also be able to improve the current handling and RF homogeneity of the resonators. Dr. Saha has been using a method of moments (MoM) simulation package (IE3D from Zeland Software) to model resonance frequency and current distribution in HTS coil designs. The MoM approach is faster and more practical for planar coils, which must be subdivided into hundreds of quasi-2D cells. It handles only planar dielectrics, but it is possible to include the cylindrical shield used in the cryoprobe. We anticipate testing a working probe during this next year. If this works, this 1 mm HTS probe will have the highest per volume S/N in any probe built to date.