High voltage electron gun for high average power FEL.

In this paper we report on the design of high-voltage (700 kV), high-power (2 MW), and long pulse (several ms) diode electron gun. It will be used as an injector for IR-Thz Freeelectron laser. Intense numerical simulations were performed with two different numerical codes - CST and COMSOL. The analytical expressions provided in the article give an idea how the shape of the electrodes affects the quality of the electron beam. The results show that the thermionic gun could produce an electron beam as good as that one generated by photo emission. It would be a reliable injector of RF LINAC to drive a cw FEL oscillator.