Vacuum and atmosphere are separated by a plasma window to facilitate nonvacuum electron-beam welding and nonvacuum material processing.

Plasma windows can separate vacuum and atmosphere, or regions of high and low vacuums, in a way which facilitates transmission of various particle beams and/or radiation from low- to high-pressure regions. In a prototype device, a stabilized plasma arc was properly configured to function as a nonsolid plasma window. Since charged particles can be focused by these arcs, focusing of such beams is a secondary function of this device.

Charged particle beams (ions, electrons) and intense x-rays are used in many applications. These beams must be generated in a high vacuum. However, in most applications (like electron-beam welding and material modification by ion implantation, dry etching, and microfabrication), it is desirable to utilize these beams at atmospheric pressure, since vacuum operation greatly reduces production rates and limits workpiece size. Also, it is desirable to raise the pressure at which electron-beam melting for manufacturing alloys is performed to facilitate manufacturing of superalloys from scrap recovery. This plasma window can facilitate nonvacuum ion material modification, manufacturing of superalloys, and high-quality nonvacuum electron-beam welding.

In vacuum systems that are used in various industrial devices, and in space vehicles, vacuum-atmosphere separation is accomplished with solid walls and windows. In the plasma window, confined ionized gas accomplishes this separation.

Three effects can enable a plasma to provide for a rather effective separation between vacuum and atmosphere, as well as between vacua regions, and even act as a pump:

1) Gas pressure effect: Pressure P (the product of density N, temperature T, and the universal gas constant R) is described by the equation P=NRT. In the plasma window T=12,000 °K compared to room temperature of 300 °K. Therefore, the plasma window matches atmospheric pressure with only 1/40 of its density.