Lattice and Component Design for the Front End Test Stand MEBT at RAL

The Front End Test Stand (FETS) linear accelerator at Rutherford Appleton Laboratory (RAL) will accelerate a 60 mA, 2 ms, 50 pps H - beam to 3MeV energy. The aim of FETS is to demonstrate perfect chopping using a novel 2 stage (fast / slow) chopper scheme. The beam chopper and associated beam dumps are located in the MEBT. Achieving a low emittance-growth under the influence of strong, non-linear space-charge forces in a lattice which has to accommodate the long chopping elements is challenging. The baseline FETS MEBT design is 4.3 m long and contains 7 quadrupoles, 3 rebunching cavities, a fast and slow chopper deflector and two beam dumps. In particle dynamics simulations using a distribution from an RFQ simulation as an input, beam loss for the unchopped beam is below 1% while the chopping efficiency is >99 % in both choppers. The final MEBT lattice chosen for FETS will be presented together with particle tracking results and design details of the beam line components.