Magnetic-field simulation for shielding from high magnetic fields

Magnetic-field simulations have been carried out to attain efficient magnetic shielding from high and static magnetic fields. A stray field created by a 10 T solenoid superconducting magnet with a phi100 mm room-temperature bore was assumed. As a shielding material, plate-, cylindrical-, and the combination of a plate- and framework-shaped irons were selected. To investigate the effect of the iron shield, the shielding factors were evaluated systematically by changing the shape, size, thickness, etc. of the shield emphasizing the area around 2 m apart from the field center in the axial direction. Various simulations led us to conclude that the shielding factor becomes high because of the use of large iron plates and not because of either the thickness or the number of layered plates. Then, the combination of a iron plate and framework was suggested and examined as a way of efficient shielding. On the other hand, when the shield was placed in the radial direction, the larger and the thicker the shield became, the higher the shielding factor. In designing magnetic shields, it is important to consider what to be shielded from and where to be shielded from stray fields. In this respect, an easy method to reduce stray fields in one direction was obtained. (C) 2002 American Institute of Physics.