Although protein crystals of high integrity in a microgravity environment have been reported, the actual implementation of these experiments are very limited. The use of magnetic force is among the most promising methods of simulating the virtual microgravity environment on earth. We have been carrying out the development of superconducting magnets for generating uniform magnetic force fields since 1997. It was not clear at the beginning of this study what configuration of superconducting coils could generate high and uniform magnetic force fields most effectively. We used a nonlinear programming method to reach an optimized design. We constructed a superconducting magnet for generating uniform magnetic force fields, whose coil parameters were based on the optimization result. The superconducting magnet was wound with NbTi conductors and designed to generate 240T2/m of the magnetic force field and 9T of the central magnetic field. This magnetic force field can cancel 17% of the gravity force for pure water. The variation of the magnetic force field is less than 1.0% in the axial component and less than 2.0% in the radial component. The uniformity of the axial component was experimentally confirmed. The magnet has now been in operation for protein crystal growth experiments.
