Formation of a Rotating Relativistic Electron Beam Using a Narrow Magnetic Cusp Field

Formation of a rotating, relativistic electron beam with properties suitable for a circular free electron laser has been studied. The rotating, relativistic electron beam is generated by the method of injecting a straight-moving, hollow, relativistic electron beam (typical energy 500 keV) into a magnetic cusp. By decreasing the axial transition width of the cusp, the beam off-centering motion is suppressed and the beam current is increased by a factor of 4 (from 50 A to 200 A).