Strong Variable Permanent Multipole Magnets

Three super strong permanent multipole magnets have been made: a fixed strength quadrupole, a variable quadrupole and a variable sextupole. The inner and outer diameters of the first 100 mm-length quadrupole are 14 mm and 100 mm, respectively. This fixed strength quad has an integrated gradient of 28.5 T; where the gradient at the center is more than 2.9 T/cm. The second, variable, quadrupole has an integrated strength of 38 T with 15 mm inner diameter and 230 mm length at the maximum: there are sixteen positions in its variable strength with about a 2 T even step width. The sextupole model is intended to change its strength at 25 Hz. One application of a variable quadrupole magnet is a final doublet quadrupole for an e+e- linear collider. Permanent magnet sextupoles are useful for focusing of cold neutrons, which are a very useful probe for material research. Strong octupoles for beam tail folding in the final focus beamline of a linear collider will also be possible with permanent magnets. These high order multipoles made from permanent magnets can achieve higher strengths, for a given bore radius, than superconducting ones. Design works are presented starting from brief review.