Development of the optimization designed electtron source for 12MV induction linac

12MV Linear induction electron accelerator was built in 1994, its electron beam source is a diode consisting of a velvet cathode and an anode with a tungsten net. A whole series of optimization designs of diode are studied by using the numerical simulation code MAGIC in order to improve the beam quality of electron source and 12MeV LIA, and the optimum diode is concluded by comparing to the results of experiment. In this way, an energy 1MeV, current >3kA, pulse width 100ns (FWHM) intense electron beam can be obtained at the output of the LIA injector.