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.
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