Development of a 700MHz low-/high- temperature superconductor nuclear magnetic resonance magnet: Test results and spatial homogeneity improvement

For the first time in nuclear magnetic resonance (NMR) magnet development, a magnet configuration comprising an insert wound with high-temperature superconductor (HTS) and a background-field magnet wound with low-temperature superconductor (LTS) has been proven viable for NMR magnets. This new LTS/HTS magnet configuration opens the way for development of 1GHz and above NMR magnets. Specifically, a 700MHz LTS/HTS NMR magnet (LH700), consisting of a 600MHz LTS magnet (L600) and a 100MHz HTS insert (H100), has been designed, built, and successfully tested, and its magnetic field characteristics were measured and analyzed. A field homogeneity of 172ppm in a cylindrical mapping volume of 17mm diameter by 30mm long was measured at 692MHz and corresponding H1 NMR signal with 1.9kHz half-width was captured. Two techniques, room-temperature and ferromagnetic shimming, were analytically examined to investigate if they would be effective for further improving spatial field homogeneity of the LH700.