NMR at 23.5 T by a resistive magnet in NIMS

Homogeneity and stability of a Bitter-type resistive magnet of National Institute for Material Science (NIMS) have been investigated at fields up to 23.5 T by means of NMR. The field homogeneity is 100 ppm over a 5 mm DSV. The field instability observed at 23.5 T contains, at least, two contributions: 1) 50 Hz fluctuations with an amplitude of 100 ppm, 2) long term drift at the rate of 50 ppm/hr. The magnet power supply may have a prime responsibility for the field fluctuations. We need an improvement of the power supply system to achieve a high resolution solid-state NMR measurement which may require stability of 10 ppm/hr. Possible applications of such a high field NMR may cover a wide range of inorganic materials including catalyzes, which consist of quadrupolar nuclei like Al, B, Ca, Cu, O, Ti, etc. We can expect that the spectra of quadrupolar nuclei would be simplified remarkably by such a high field magnet.