Design and test of a 700 mm long hexapole composed of rectangular rare earth cobalt permanent magnets

A hexapolar magnet with inner diameter of 80 mm and an air gap inductance of > 400 mT on the pole faces is described. This magnet consists of six parallelepiped rare earth cobalt permanent magnet bars, 17 × 700 mm²in cross section and 42.1 mm in height. The whole device, which is used as part of an ECR-Heavy Ion Source, is placed into a magnetic mirror field with strong axial field strength. To assure a proper superposition of the hexapole field and mirror field, no iron Circuit could be used. The radial and axial field distribution inside the hexa-pole magnet was measured, and compared with calculated data. The variation of field strength, especially the variation of lines with constant field strength as a function of both the height and width of the magnets is discussed.