Magnetic field along central axis for periodic permanent magnetic focusing system with open magnetic rings

Based on the current element model for magnetic ring, the magnetic field distribution along central axis was analyzed for permanent magnetic ring. Theoretical calculation and measured results show that the whole magnetic ring only exhibits an axial magnetic field without radial component. For the open magnetic ring with a gap, the axial magnetic field decreases and the radial magnetic field increases, producing a non-axis-symmetrical magnetic field along central axis. Therefore, the application of the open magnetic ring in periodic permanent magnet(PPM) focusing system is limited. The structure of the PPM focusing system with open magnetic rings was proposed and optimized, according to the distribution characteristic of the axial magnetic field and radial magnetic field, and the periodic m