The paper presents experimental and theoretical research data on the generation, transport, and extraction of a large cross-section (750 × 150 mm2) electron beam into the air through a thin metal foil in an accelerator with a mesh plasma cathode on the bases of a low-pressure arc and with a multi-aperture two-electrode electron-optical system. When the burning conditions of the arc discharge, responsible for the generation of the emission plasma, is changed, the characteristics of this plasma were investigated, including under the conditions of the selection of electrons from it. Our experiments show that at an accelerating voltage of 200 kV, current in the accelerating gap of up to 30 A, and full width at half maximum of up to 100 µm, the average extracted power is ≈4 kW and the extracted beam current is ≈85% from the common current into the accelerating gap. Our numerical estimates give a good correlation between the arc and emission plasma parameters depending on the electrode configuration in the discharge system and on the mechanism of electron beam generation. Analysis of the emission plasma parameters under different arc conditions and of the mechanisms responsible for the beam energy loss suggests that most of the energy in the accelerator is lost at the support grid and at the output foil due to defocusing of the beam and partial electron reflection from the foil. Other mechanisms that decrease the extracted beam energy are discussed.

The remaining challenges, confronting high-power microwave sources and pulsed power technology, stimulate the development of robust relativistic electron beam sources. This paper presents a carbon-fiber-aluminum cathode with high-density uniform emitters, which was tested in a single pulsed power generator (~450 kV, ~350 ns, ~50 Ω) and a repetitive one (350 kV, <10 ns, 150 Ω, and 100 Hz). The distribution and development of the cathode plasma was observed by time-and-space resolved diagnostics, and the uniformity of electron beam density was checked by taking x-ray images. A quasi-stationary behavior of the cathode plasma expansion was observed. It was found that the uniformity of the extracted electron beam is satisfactory in spite of individual plasma jets on the cathode surface. Under repetitively pulsed operation, this cathode exhibited a good shot-to-shot reproducibility even in poor vacuum. This new class of plasma cathodes offers a promising prospect of developing relativistic electron beam sources.

High-current electron beams with a current density of up to 100 A/cm2 generated by a plasma-cathode gas-filled diode at low accelerating voltages are studied. Two types of gas discharges are used to produce plasma in the cathode. With glow and arc discharges, beam currents of up to 150 A and 400 A, respectively, have been obtained at an accelerating voltage of 16 kV and at a pressure of 1–3·10−2 Pa in the acceleration gap. The ions resulting from ionization of gas molecules by electrons of the beam neutralize the beam charge. The charge-neutralized electron beam almost without losses is transported over a distance of 30 cm in a drift channel which is in the axial magnetic field induced by Helmholtz coils. The results of calculations for the motion of electrons of the charge-neutralized beam with and without axial external field are presented and compared with those of experiments.