Uniform transverse beam profile with a new type of nonlinear magnet

In this paper, a new type of magnet is proposed and produced to give a uniform transverse beam profile.Compared to octupole magnets, the new type of magnet can provide a similar octupole magnet field in the middle,but the rise rate declines quickly at the edges, so that a beam of the same uniformity is obtained with less particle loss.Besides that, a mechanical structure is added to adjust the width of the middle region to satisfy different transverse dimensions, which would further reduce particle loss. Some numerical simulations have been done with the octupole and the new type of magnet to show the advantages of the new magnet.