Simulation of Electron Beam Dynamics in a Nonmagnetized High-Current   Vacuum Diode
  The electron beam dynamics in a nonmagnetized high-current vacuum diode is analyzed for different cathode-anode gap geometries. The conditions enabling to achieve the minimal {initial} momentum spread in the electron beam are found out. A drastic rise of current density in a vacuum diode with a ring-type cathode is described. The effect is shown to be caused by electrostatic repulsion. 
Sergey Anishchenko and Alexandra Gurinovich
physics.plasm-ph physics.acc-ph