Current density distribution in a large cross-section beam in an electron accelerator with a multiaperture plasma cathode

An electron accelerator with a multiaperture plasma cathode with grid stabilization of the boundary of emission plasma based on a low-pressure arc discharge generating a large cross-section (750 $\times$ 150 mm$^2$) beam with its ejection into the atmosphere or high-pressure gas through the exit foil window is described. A comparatively simple method for decreasing the nonuniformity of the current density distribution over the beam cross section using a mask with variable-diameter holes is proposed and experimentally tested. In this case, the higher the plasma concentration in the emission region, the smaller the diameter of the holes in the mask. When this mask was used, the nonuniformity of the current density distribution was decreased from $\pm$15 and $\pm$10% to $\pm$10 and $\pm$5% on the long and short sides of the beam cross section, respectively.