Sensitivity of Cryogenic Solenoidal Probe for Split-Pair Superconducting Magnet With Cross-Bore

By using a split-pair superconducting magnet with cross-bore, one can implement a solenoidal radio frequency (RF) coil for solution nuclear magnetic resonance (NMR). We expect the solenoidal RF coil to give us higher sensitivity than an ordinary saddle-shaped RF coil. We have developed both room temperature and cryogenic NMR probes with a solenoidal RF coil for a split-pair superconducting magnet. The probes and the solenoidal RF coils were evaluated using a sensitivity test with standard 0.1% ethylbenzene. The sensitivity tests of the room temperature probes indicated that the signal-to-noise ratio (SNR) of the solenoidal RF coil was higher than that of an ordinary saddle-shaped RF coil. In the sensitivity test of the cryogenic probe, we compared a four-turn solenoidal RF coil with a two-turn one. As a result, the SNR of the one of two-turn RF coil was higher than that of the one of the four-turn one. It is believed that the reason is that the SNR depends on the quality factor of the specimen Qs and, furthermore, Qs depends on the shape of the RF coil.