Design study of superconducting magnets for uniform and high magnetic force field generation

Magnetic force is one of the most promising tools to realize a virtual microgravity environment on earth. It has recently been found that the growth of protein crystals might be affected by microgravity offing to the suppression of the convectional flow. We started the development of superconducting magnets for the generation of uniform and high magnetic force fields to suppress convectional flow. As it was not clear what configuration of superconducting coil could generate most effectively high magnetic force fields, while they maintain their uniformity. For this purpose, we used a nonlinear programming method. The results obtained clarified that a magnet whose inner coil is longer than the outer one can generate more uniform and higher magnetic force fields in a long sample space. A superconducting magnet generating a magnetic force field of 240 T-2/m has already been constructed with NbTi conductors at the Tsukuba Magnet Laboratory. We have also completed the design of a superconducting magnet composed of Nb3Sn and NbTi conductors to generate uniform magnetic force fields up to 882T(2)/m.