I. Introduction
The technological application of high-power pulsed electron beams to surface modification of metal and cermet materials and products is progressing rapidly [1]–[4]. Low-energy (up to 30 keV) high-current electron beams whose energy density ranges from a few to hundreds of joules per square centimeter at microsecond and submillisecond pulse durations are particularly promising. The action of beams of this type on metal materials in vacuum results in melting of the surface, in its smoothing by surface tension forces, and in structural modification of the surface layer for a depth from several micrometers to tens of micrometers. Electron sources with a grid plasma cathode [5], [6] have well-known advantages such as long lifetime, high energy efficiency, and high uniform current density at a rather large emission surface (up to 100 ). They also feature the possibility for smooth and independent tuning of the beam main parameters over a wide range and the capability of producing beams of long current pulse duration at high repetition rates (up to 1 kHz). In many cases, electron sources of this type are favored in technologies of pulsed thermal surface treatment of materials and products. To improve the performance of currently available plasma-cathode electron-beam sources and to design and manufacture new ones, investigations on the beam generation and transport in gas-filled gaps are necessary.