Linac4 source extraction re-design for higher current operation

At the end of LS2, Linac4 will become the new injector of proton beams to the entire CERN accelerator complex. The maximum beam current reliably achieved so far in commissioning is 25 mA, well below the initial specifications of 40 mA. This is mainly due to the presence of pre-injector limitations, and in particular to extracted beam emittance exceeding the acceptance of the RFQ. A new geometry of the Linac4 source extraction electrodes has been the object of the study presented in this note, with the aim of decreasing the extracted beam emittance and increasing the H- beam current that can fit in the RFQ acceptance. The new source layout was studied with the CST Particle StudioTM [1] and IBsimu [2] codes. Encouraging simulation results prompted the launch in production of a new flange and extraction electrodes that should be tested with beam at the source test stand before the end of the year.