In this paper, the design and simulation of an electron injector based on a thermionic RF modulated electron gun for particle accelerator applications is presented. The electron gun is based on a gridded thermionic cathode with the geometry based on a Pierce-type configuration. Both theory and numerical simulation were used to explore the relationship between the bunch length and charge. The reasons for the pulse widening were also analyzed. The beam dynamics simulations showed that a minimum pulse length of 106 ps could be achieved with a bunch charge of 33 pC when the driving RF frequency was 1.5 GHz. The average transverse emittance was about 17 mm⸱mrad from the particle-in-cell simulations. Operating at a higher RF frequency did not significantly reduce the micro-pulse length.

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