Construction and test results of a compact 0.8 meter warm bore 1.5-tesla high-homogeneity superconducting magnet for MR-spectroscopy

A superconducting magnet aimed at whole body MRI (magnetic resonance imaging) and spectroscopic studies was designed, constructed, and tested. The magnet was wound with a 2-mm-diameter NbTi/Cu multifilamentary composite conductor. The design field was B ₀=1.5 T; the design value for field homogeneity ΔB /B₀=0.1 ppm over a 20-cm-diameter spherical volume; and the design value for the field stability dB₀ /dt/B₀<0.1 ppm/h. During construction of the magnet, emphasis was put on evaluating the winding accuracy attainable in practice. Dimensional measurements on the coil were compared with subsequent field measurements. The magnet was designed to be fully self-protective in the event of a quench. The quench calculations were verified by test quench measurements. The magnet was cooled by immersion in a 300-liter LHe bath of an annular helium cryostat having a 0.8-m-diameter GRP (glass-fiber-reinforced plastic) room-temperature bore tube, with a 7 l/d LHe boil-off