Computer simulation of the UMER electron gun

An important feature of the UMER experimental program is the continuing use of comparisons between computer simulation and experimental measurement. These comparisons have, for example, explained several significant features observed in the prototype injector experiment. Therefore, during assembly and testing of the UMER injector, two- and three-dimensional simulations are being conducted with the aim of understanding the space-charge-dominated physics in the gun and injector transport sections, as well as interpreting the experimental data. These simulations are important for providing a realistic initial beam distribution for beam dynamics simulations in the main ring. The emphasis here is on simulating the beam propagation in the gun region between the cathode grid and the anode grid for measurement comparisons at the gun structure exit