Optimisation of the PERLE Injector
Résumé
The injector for PERLE, a proposed electron Energy Recovery Linac (ERL) test facility for the LHeC and FCC-eh projects, is intended to deliver 500 pC bunches at a repetition rate of 40.1 MHz for a total beam current of 20 mA. These bunches must have a bunch length of 3 mm rms and an energy of 7 MeV at the entrance to the first linac pass while simultaneously achieving a transverse emittance of less than 6 mm mrad. The injector is based around a DC photocathode electron gun, followed by a focusing and normal conducting bunching section, a booster with 5 independently controllable SRF cavities and a merger into the main ERL. A design for this injector from the photocathode to the exit of the booster is presented. This design was simulated using ASTRA for the beam dynamics simulations and optimized using the many objective optimization algorithm NSGAIII. The use of NSGAIII allows more than three beam parameters to be optimised simultaneously and the trade-offs between them to be explored.