Yasuhiko Terada1, Hirotaka Fujisaki1, Katsumi Kose1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
We experimentally evaluated the effects of permanent magnetic circuits on gradient field linearity. The gradient field generated by a gradient coil set differed when it was inserted in different magnetic circuits. For a magnet with a wide gap compared with the coil gap, the field linearity was as large as the calculated one. For a magnet with a narrow gap close to the coil gap, the gradient field linearity significantly decreased. This is because of the mirror image currents flowing in the pole pieces. This indicates that the design of gradient coils requires consideration of the mirror current effect.