Development of Combined-Function Multipole Permanent Magnet for High-Intensity Beam Transportation

Space charge compensation technology using higher-order multipole magnetic field components has been proposed to transport high-intensity charged particle beams. In order to realize this compensation technology in a limited beam line space, we devised a compact-size combined-function multipole permanent magnet. This magnet can produce two multipole components at the same location on the beam line. As a first step, we have designed a magnet to simultaneously generate a fixed-strength quadrupole and an adjustable-strength octupole component using permanent magnet materials. In this magnet model, the magnetic circuit consists of two groups of magnets. The first one is a group of trapezoidal magnets that occupy most of the space to generate a quadrupole magnetic field component with a magnitude of 30 T/m. The second one is an inner group of cylindrical magnets to generate an octupole component with a magnitude up to 17,000 T/m
³
. The intensity of the octupole component can be varied from 17,000 T/m
³
to 0 T/m
³
by rotating these cylindrical magnets. This design was used to build a prototype model. In this model, the modulation mechanism was implemented to verify the feasibility of the modulation scheme for the octupole magnetic field strength.