Dependence of Thermionic Gun Emittance on Beam Energy Calculated with EGUN

The dependence of the emittance of a thermionic diode gun on the gun voltage for a constant beam current density was investigated. Therefore the EGUN code for electron gun simulations had been installed for public access on the UNIX/RSPLUS network. It was used to calculate the trans-verse emittance at the exit of a thermionic diode gun which is an option in the main beam injector scheme of CTF-3. For a constant current den-sity of 7.5 A/cm2 and gun voltages from 65 kV to 260 kV the normalized transverse emittance was found to be constant at about 1.7 mm mrad. 1 The simulation code EGUN The program EGUN was written by W.B. Hermannsfeldt [1] to simulate the dy-namics of charged particle beams in electron guns. It solves the two dimensional Poisson equation with boundary conditions given by the gun geometry and the applied voltages. Magnetic fields are taken into account by the iterative solution algorithm. After convergence of the Poisson solver a maximum number of 5