Cavity design for the CERN muon cooling channel

The cooling channel of the CERN reference scenario [1] for a possible neutrino factory [2] requires an approximately 200 m long lattice, which provides solenoidal magnetic fields plus longitudinal electric fields at the same time. The electric real estate field gradient along the structure shall be 2 MV/m at 44 MHz, or 4 MV/m at 88 MHz, respectively. The CERN approach incorporates the solenoids into the cavity geometry in order to avoid the large dimensions of solenoids surrounding the cavity structure. Since the idealistic assumption of a constant solenoidal field along the cooling channel is broken by this approach, an iteration between beam dynamics requirements and RF engineering feasibility is necessary to define an optimized structure. In this paper we describe the various cavity design options that have been considered up to now and we report on the preparation of a cavity test stand for a 88 MHz cavity.