Air boring and nonvacuum electron beam welding with a plasma window

Abstract

The plasma window is a novel apparatus that utilizes a stabilized plasma arc as interface between vacuum and atmosphere or pressurized targets without solid material. Additionally, the plasma has a lensing effect on charged particles. This feature enables beam focusing to very small spot sizes and overcoming beam dispersion due to scattering by atmospheric atoms and molecules. Recently, the plasma window was mated to a conventional electron beam welder. And, electron beam welding in atmosphere was accomplished with electron beams of unprecedented low power and energy. Weld quality for the nonvacuum plasma window electron beam welding approached the quality of in-vacuum electron beam welding, without the use of helium as process gas. Weld widths were independent of stand-off distance for up to 5cm, which along with visual observations suggest that pinched beam propagation might have been achieved with 6–25mA, 90–150KeV electron beams. That may explain the better than expected welding results. By comparison previously demonstrated self-pinched propagation used kA MeV electron beams.