Development and testing of superfluid-cooled 900 MHz NMR magnet

• Published in: Cryogenics (Guildford) Vol. 41; no. 9; pp. 623 - 630
• Main Authors: Nagai, Hideo, Sato, Akio, Kiyoshi, Tsukasa, Matsumoto, Fumiaki, Wada, Hitoshi, Ito, Satoshi, Miki, Takashi, Yoshikawa, Masatoshi, Kawate, Yoshio, Fukui, Shigeo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2001; Elsevier
• Subjects: Applied sciences; Cryogenics; Cryostats; Energy; Energy. Thermal use of fuels; Exact sciences and technology; He II systems; Magnetic resonance spectrometers; Magnets; Natural frequencies; NMR magnets; Nuclear magnetic resonance spectroscopy; Refrigerating engineering. Cryogenics. Food conservation; Rupture disks; Safety valves; Superconducting materials; Supercooling; Superfluid helium; Superfluid helium; He II systems; NMR magnets; Cryostats; Cooler; Cryogenic fluid; Magnet; Cryogenics; Superfluid; Helium II; Nuclear magnetic resonance
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/S0011-2275(01)00134-5

As the preliminary step for the 1 GHz NMR spectrometer, a 900 MHz class NMR magnet was fabricated and was successfully operated in December 1999. The magnet is made of 15% Sn–bronze-processed (Nb,Ti) 3Sn, Ta-reinforced (Nb,Ti) 3Sn, and NbTi conductors. All the coils are cooled with pressurized superfluid helium. The magnet generated a field of 21.20 T in a driven mode and then operated in a persistent mode at 21.17 T corresponding to a proton NMR frequency of 901.2 MHz. During the magnet excitation for 24 h, the superfluid bath temperature was kept constant to below 1.6 K using an automatic control system. After several excitation tests, the magnet was quenched and the rupture disk of the magnet vessel was broken. The size of the cold safety valve and the structure of the rupture disk have been checked and modified. Before the reassembly of the magnet cryostat, the modified superfluid cooler for cooling the magnet bath was tested.