3D Modeling of the ALICE Photoinjector Upgrade

The injector for the ALICE machine (Accelerators and Lasers In Combined Experiments) at Daresbury Laboratory is based around a 350 kV DC photocathode electron gun. An upgrade is proposed to introduce a load‐lock GaAs photocathode preparation facility to allow rapid transfer of photocathodes to the gun without breaking the vacuum system. In the current design this requires side‐loading of the photocathodes into the cathode ball. An alternative is to relocate the ceramic insulator vertically which will allow back‐loading and also backillumination of the photocathodes. 3D electrostatic simulations of the gun chamber are presented for both options along with 3D beam dynamic simulations for an off‐axis photocathode, introduced to increase photocathode lifetime by reducing damage by ion backbombardment. Beam dynamic simulations are also presented for the entire injector beamline as well as for a proposed extension to the injector beamline to include a diagnostic section.