DEVELOPMENT OF 750MHZ SUPERCONDUCTING PROBE

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。超导NMR探头包含由超导材料制成的冷却RF线圈，从而改善了实验的信噪比。这些都是在500和600 MHz的商业可用，核心3的目标是与NHMFL和布鲁克仪器的同事合作，在750 MHz构建改进的探针。 在2003年春天，我们改变了我们的目标，600 MHz 1毫米HCN探头与单轴脉冲场梯度。威瑟斯已经建立了安装硬件和13 C和2 H线圈。他们现在正在构建1H和15 N线圈，他们最初的尝试导致1H线圈的谐振频率比预期的高约5%。他们测试的这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。 更多的超导晶片将很快推出，在NHMFL博士后研究员Saikat Saha的帮助下，我们在建模和更好地理解HTS谐振器的行为方面也取得了真实的进展。看来，有了这种更好的理解，我们可以提高我们的能力，设计新的频率和尺寸要求，但我们也可能能够提高电流处理和射频均匀性的谐振器。Saha博士一直在使用矩量法（MoM）仿真软件包（来自Zeland Software的IE 3D）对HTS线圈设计中的谐振频率和电流分布进行建模。MoM方法对于平面线圈更快且更实用，平面线圈必须细分为数百个准2D单元。它只处理平面屏蔽，但可以包括冷冻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针。如果这起作用，这种1 mm HTS探头将在迄今为止构建的任何探头中具有最高的单位体积S/N。

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.