The article studies the generation of small-diameter focused electron beams using electron-optical system of a welding gun with plasma cathode. The results show that the beams always form in the electron-optical system with plasma cathode when the gas in the region of beam emission, acceleration and transportation is present. The presence of the gas causes positive volumetric charge formation during the passage of electrons. This charge electrically neutralizes the beam, and in some cases can lead to overcompensation of its electron charge. The compensation of the volumetric charge in the region of beam formation and acceleration is the principal discrepancy of an electron-optical system with plasma cathode from a thermal cathode system. It is demonstrated that the brightness of the electron beam from a plasma cathode gun meets that of the beams from a thermal cathode gun. The paper describes the electron gun featuring voltage up to 120 kV and presents images of polished samples of weld penetration in stainless steel and titanium in vacuum. The gun served as the basis of a device for ejecting electron beam into the atmosphere. It is shown that the pressure rise up to the atmospheric one is provided through two gas-dynamic stages. The main characteristics of the atmospheric gun are given.
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