Journal
SUPERCONDUCTOR SCIENCE & TECHNOLOGY
Volume 29, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0953-2048/29/2/024006
Keywords
coated conductor; dipole magnet; field quality; hadron cancer therapy; high T-c superconductor tape; magnetisation; screening current
Categories
Funding
- Japan Agency for Medical Research and Development (AMED)
- Ministry of Economy, Trade and Industry (METI) in the Development of Fundamental Technologies
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Electromagnetic field analyses were carried out to study the influence of coated-conductor magnetisation, i.e. the screening (shielding) current, on the field quality of a dipole magnet in a rotating gantry for hadron cancer therapy. The analyses were made on the cross section of a cosine-theta dipole magnet in a rotating gantry for carbon ions, which generated 2.90 T of magnetic field. The temporal profile (temporal variation) of the magnet current was determined based on the actual excitation schemes of the magnets in the rotating gantry. The experimentally determined superconducting property of a coated conductor was considered, and we calculated the temporal evolutions of the current-density distributions in all the turns of coated conductors in the magnet. From the obtained current-density distributions, we calculated the multipole components of the magnetic field and evaluated the field quality of the magnet. The deviation in the dipole component from its designed value was up to approximately 25 mT, which was approximately 1% of the designed maximum dipole component. Its variation between repeated excitations was approximately 0.03%, and it drifted approximately 0.06% in 10 s. Some compensation schemes might be required to counteract such influence of magnetisation on the dipole component. Meanwhile, the higher multipole components were small, stable, and sufficiently reproducible for a magnet in rotating gantries, i.e. vertical bar Delta b(3)vertical bar similar to 1.1 x 10(-3) and vertical bar Delta b(3)vertical bar similar to 0.2 x 10(-3) in 10 s.
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