High-viscous Ar plasma generation for plasma window application to electron beam welding in atmosphere

Plasma window has been paid attention as an innovative technique, by which a dense plasma can separate vacuum from atmosphere. The promising applications of the plasma window enable us to transmit charged particles and X-ray through plasma channel without significant beam scattering and attenuation, although a neutral gas flow is frozen effectively due to a high-gas viscosity. Thus, our application is to weld/cut the substances by an electron beam in air atmosphere. Note that the plasma windows make it possible to realize that the size of work piece for the welding is substantially mitigated, capable of applying this method to large structures that requires precise fabrications in air.

In general, a cascade arc discharge plasma source has been employed to generate atmospheric dense plasma. However, the pressure difference between the plasma window was 100 kPa and ~100 Pa, so that further increase of the gas viscosity is essential to realize the practical plasma window. Thus, we have developed a cascade arc device to demonstrate the pressure separation of 100 kPa-1 Pa by improving the electrodes structure and material, by which we expect to increase the gas viscosity considerably.