A home-built Halbach magnet array was used to provide a 100 mT static magnetic field over a cylindrical region in space of 22 mm radius and length 150 mm in which the precipitation and redissolution procedure was carried out. This was achieved by arranging two rings of 8 0.5×0.5×2 inch neodymium magnets (1.4 T remanence) in a cylindrical Halbach dipole array, with the magnet centers lying on a circle of radius 45 mm.