Precision modeling of grid fields and beam dynamics in a large-aperture accelerator for an electroionization laser

The accelerator considered is a planar tetrode-type system. It contains a grid of lengthy glowers emitting beamlets, which cover an anode exit window of 6600 cm2 in area. Key parameters of the system, i.e. maximal extracted current, continuous service life and reliability, depend directly on the physical properties of the exit window foil, as well as non-uniformity in density of the accelerated beam. Adequate computer simulation is necessary in designing the latter. In this paper, careful modeling of electrostatic fields, which are highly nonlinear near the grid rods of small diameter, has been performed using the boundary collocation method. Stray magnetic cathode fields were found analytically. Electron ray tracing in these fields provided useful information on abnormal local heating of the foil due to aberrations in the beamlets.