Influence of particle fluxes from target on characteristics

Transportation of Intense Electron Beams of µs Duration in Vacuum: Beam Characteristics and Beam Target Interaction

V. Engelko¹, G. Mueller² ,H. Bluhm²

1- Efremov Institute of Electrophysical Apparatus, 189631, St. Petersburg, Russia

2- Forschungszentrum Karlsruhe, Institut für Hochleistungsimpuls- und Mikrowellentechnik, Postfach 3640, D-76021 Karlsruhe, Germany

The application of pulsed intense electron beams for material surface modification to improve the wear, corrosion and oxidation resistance, fatigue strength etc. is an attractive technology and promising industrial perspectives to predict the treatment results and to get stable, reproducible results it is necessary to perform investigations on formation and transportation of pulsed intense electron beams and their interaction with matter.

When an intense electron beam interacts with matter the following processes take place:

A part of electrons is reflected back to the source. This leads to a decrease of the electron beam current and redistribution of the beam energy inside the target.

Heating the target results in melting and evaporation of the target material and gas desorption from its surface.

Hydrodynamic processes in the melted layer take place, which are responsible for material mixing and surface relief formation after irradiation.

Ionisation of desorbed gases and vapours from the target material leads to formation of a target plasma and ion flux.

The ion flux influences the electron beam current density distribution.

The target plasma influences the beam transportation and the state of the target surface after irradiation.

Beam transport by applied magnetic field can lead to a rotation of the beam. In this case the current distribution at the target will become modulated in time and space.

Investigations have been carried out with the help of measurements of accelerating voltage U, beam current I, controlling grid current Ig and grid potential Ug, beam current density distribution j(r), intensity of x-ray radiation and its temporal and spatial distribution at the target, beam potential in the drift channel, and so on. Theoretical and numerical investigation related to the mentioned topics were also conducted.

Some of the aspects described above also be presented more detailed in separate papers at this conference. This paper gives an overview about the different effects influencing the characteristics of intense electron beams transported in vacuum.