Computer Simulation of the Umer Electron Gun*

* Work supported by the U. S. Department of Energy at NRL under contracts DE-AI02-93ER40799 and DE-AI02-94ER54232, at U. Md. under DE-FG02-92ER54178 and DE-FG02-94ER40855, and at the HIFVNL under DE-AC03-76SF00098 and W-7405-Eng-48. Abstract An important feature of the UMER experimental program [1,2] is the continuing use of comparison 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 twoand threedimensional 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 experimental data. These simulations are important to providing a realistic initial beam distribution for simulating beam dynamics in the main ring. Emphasis here is on simulating the beam propagation in the gun region between the cathode grid and the anode grid for comparison with measurements at the exit from the gun structure.