Energy Density Distribution in the Cross Section of a Radially Converging Low-Energy High-Current Electron Beam

The energy density distribution of a radially converging low-energy (up to 25 keV) high-current electron beam has been measured using a sectioned three-channel calorimeter. The beam formation was performed using a two-sectioned cathode assembly. Eighteen resistively decoupled arc plasma sources triggered by a breakdown over the dielectric surface were built in the 4-cm-radius ring cathode of each section. The distance between the centers of sections was 4 cm. Measurements were performed both in the vacuum-diode mode (a pressure of residual gases of 0.006 Pa) and in the gas-filled diode mode (argon at a pressure of 0.08 Pa). It has been shown that the energy density in the central part of the beam is higher by 25–30% on average than in its peripheral parts; this can be acceptable for solving many tasks of surface modification of metals and alloys. Lifetime tests of the cathode assembly have shown its operation stability for 50 000 pulses in minimum.