期刊
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
卷 33, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1361-6668/ab601d
关键词
REBCO magnet; ferromagnetic shim; homogeneity reproducibiliy; NMR
资金
- KBSI grant [D39611]
- National Research Council of Science & Technology (NST), Republic of Korea [D39611] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
We report that the field homogeneity of a large-scale metal-clad no-insulation all-ReBa2Cu3O7-x magnet is reproducible after occasional operating conditions, in this case the current ramp down/up and magnet warm-up/cool-down conditions. First, we shimmed the magnet by cylindrically arraying ferromagnetic shims on the wall of the room-temperature bore of the magnet to improve the spatial field homogeneity. As a result, the field homogeneity of the magnet was improved from 557.7 to 14.1 ppm in a 10 mm diameter spherical volume. The resultant acquisition of field homogeneity tremendously enhanced from an inhomogeneous state greatly degraded by screening currents qualified us to study the temporal stability of the field homogeneity. We used a magnet-energizing protocol with the field drift minimized to shrink a nuclear magnetic resonance (NMR) lineshape into a much narrower super-imposable lineshape. We demonstrate the technique by NMR experiments, showing excellent reproducibility in every case, presenting strong evidence of recovery to certain time-unvarying field gradients and to a state of homogeneity. These findings suggest a new route for high-resolution high-temperature superconducting NMR and magnetic-resonance-imaging magnet technology.
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