Hybrid race-track microtron end magnets

A more compact, efficient, and reliable Race Track Microtron magnet design is achieved with Permanent Magnet Material and iron poles and yokes. In analytical design calculations we represent the PMM with magnetic charge sheets and permeabilities of the order 1.03-1.1 to obtain values for the geometry, amount and placement of iron and PMM, and so on. In the following detailed analysis/design, we use finite element codes. Our magnet is a PMM-excited iron box-pole structure, with slots for the RTM beams and a reverse potential/field pole at the entrance/exit to obtain the required fringe field distribution. Iterating with beam dynamics simulations, we find the pole dimensions, position, and reverse pole potential that provide beam focusing and allow the accelerating structure to be cleared.