The Pulsed Electron Beam Facility GESA: Device and Physics

Pulsed electron beam treatment is used to modify the surface layer of metal targets while leaving the bulk material unchanged. Appropriate for such treatment are pulsed electron accelerators of the GESA family. A high voltage pulse, typically around 100 kV, is generated and applied to a large-area cathode. The extraction voltage of the triode system controls the electron emission. The electron beam is then transported in a guiding magnetic field and focused on the target. Beam-target interaction leads to melting of the target surface up to a depth of tens of micrometres. After termination of the electron beam, rapid cooling and re-solidification results in a modified surface layer with improved properties.
In this presentation, the pulsed electron beam devices GESA are introduced. An overview on the physics of their operation is given, including electron emission, beam formation and transport, and interaction of the electron beam with the target. Finally, heat transfer in the target is considered and specifications of the treatment such as melt depths and cooling rates are given.