Superconducting magnets for generating uniform magnetic force field

We report a new application of high magnetic fields to structural biology. We usually design and fabricate a magnet to achieve uniform magnetic field as well as uniform magnetic field gradient. In this new application we adopt a uniform magnetic force field. It has been found that the growth of protein crystals is affected by the presence of magnetic force. Development of uniform magnetic force field magnets is now in progress at the Tsukuba Magnet Laboratory of the National Research Institute for Metals. These magnets are superconducting magnets because they must be continuously run for several days to grow protein crystals. The first magnet wound with NbTi is now under installation. This magnet is designed to generate a uniform force field of 240 T/sup 2//m in a cylindrical space of 10 mm in diameter and 10 mm in height, and the magnetic force field fluctuation along z-direction is better than 0.4%. In liquid helium, it could achieve the design current.