A Novel Method for Transport and Cooling of a Muon Beam Based on Magnetic Insulation

Unwanted field emission is a well known problem for high-gradient accelerating structures as it can cause damage and initiate breakdown. Recent experiments indicated that the deleterious effects of field-emission are greatly enhanced in the presence of external magnetic fields. In the context of designing a muon accelerator this imposes numerous constraints since rf cavities need to operate within strong magnetic fields in order to successfully transport the beam. Here, a novel design of a magnetically insulated cavity in which the walls are parallel to the magnetic field lines is presented. We show that with magnetic insulation, damage from field emission can be significantly suppressed. Effects of coil positioning errors on the cavity performance are discussed and the required magnetic field strength to achieve insulation is estimated. We present a conceptual design of a muon collider cooling lattice with magnetic insulated cavities and cross-check its performance to the one with pillbox cavities. Finally an experiment to test magnetic insulation is described.