Broadband electron gun design for a 5 T solenoid Electron Beam Ion Source for hadron therapy

The design and optimization of a broadband electron gun with a semi-immersed cathode for an Electron Beam Ion Source (EBIS) operating with a 5 T solenoidal magnetic field is presented. The work contributes to the development of high-performance, tunable EBIS for next-generation all-linac medical accelerators for cancer therapy, as well as other applications in accelerator physics. The system is primarily designed to meet the requirements for the production of fully stripped carbon ions. An acceptance criterion for the injection of the electron beam into a full magnetic field is derived and used to validate the design. The gun position is optimized for the transmission of an electron beam with a current of 2.0 A and a current density of 1000 A / cm 2 inside the solenoidal field. The operating range of the electron beam can be broadened from 0.2 to 3 A by using a nonadiabatic magnetic field on the beam path close to the gun, which transfers the transverse component of the electron energy into the longitudinal direction and therefore reduces the amplitude of the beam scalloping. The current density can be adjusted by the use of another coil surrounding the cathode.