Production and application of low-energy, high-current electron beams

TLDR

LEHCEBs face challenges in initiating explosive emission and transporting beams in plasma-filled diodes, while also influencing surface phase transformations of irradiated materials. The article reviews experimental work on producing low-energy, high-current electron beams and their application to surface modification of materials. It describes methods to improve beam energy density uniformity, calculates nonstationary temperature and stress fields in targets, and evaluates beam transport in plasma channels. Experiments show that plasma-anode, explosive-emission cathode guns are most promising, that short accelerating voltage rise times boost cathode field strength and current density, that beam currents exceed the Pierce limit by 1–2 orders of magnitude, and that such beams generate nonequilibrium structure–phase states in quenched surface layers.

Abstract

This article reviews experiments on the production of low-energy, high-current electron beams (LEHCEB) and their use for surface modification of materials. It is shown that electron guns with a plasma anode and an explosive emission cathode are most promising for the production of this type of beams. The problems related to the initiation of explosive emission and the production and transportation of LEHCEBs in plasma-filled diodes are considered. It has been shown that if the rise time of the accelerating voltage is comparable to or shorter than the time it takes for an ion to fly through the space charge layer, the electric field strength at the cathode and the electron current density in the layer are increased. Experimentally, it has been established that the current of the beam transported in the plasma channel is 1–2 orders of magnitude greater than the critical Pierce current and several times greater than the chaotic current of the anode plasma electrons. Methods for improving the uniformity of the energy density distribution over the beam cross section are described. The nonstationary temperature and stress fields formed in metal targets have been calculated. The features of the structure-phase transformations in the surface layers of materials irradiated with LEHCEBs have been considered. It has been demonstrated that in the surface layers quenched from the liquid state, nonequilibrium structure-phase states are formed.