RF design options for a 180 mev H- linac for megawatt beam facilities

Future projects like a neutrino factory or an advanced spallation neutron source require high power proton accelerators capable of producing beams in the multi-MW range. The quality of the beam delivered to the target is very much dictated by the accelerator front end and by the lower energy linac. Prompted by the front end test stand (FETS) under construction at RAL, a new 180 MeV FT linac is being considered as a possible replacement for the aging current 70 MeV ISIS injector, and the same linac has also been included in designs for the proton driver for a possible UK neutrino factory. In this paper, different RF design options are analysed and a general layout for the new linac is presented based on two accelerating structures to raise the beam energy from 3 to 180 MeV: a 324 MHz drift tube linac (DTL), making use of commercial Toshiba klystrons, followed by side coupled linac (SCL) with a triple frequency jump at the transition between the two structures.