2) Viscosity effect: Viscosity (friction, resistance to flow) of a gas increases with temperature. Consequently gas flow through a hot plasma-filled channel is substantially reduced compared to a room-temperature gas-filled channel.

3) Pumping effect: Gas atoms and molecules are ionized by plasma electrons and are trapped by the fields confining the plasma window. Experimentally, these effects contributed to a factor of 228.6 pressure reduction over differential pumping. (Details of the theory and the experiments can be found in A. Hershcovitch, Journal of Applied Physics, 78 [9], 5283 [1995].)

Plasmas act as lenses on charged particle beams in general. The currents in this plasma window generate azimuthal magnetic fields which deflect (focus) the particles radially inward (via the Lorentz force). This plasma lens is stronger than the general case where the beam-generated field focuses. More details can be found in the paper cited above.

Curiously, the plasma window functions in a way which very superficially resembles the force field in the Star Trek TV series. For example, there is an area on the Enterprise (the Shuttle Bay) from which shuttle crafts leave for flights into space. At the edge of that area there is a force field (with a bluish glow at its perimeter) which separates the atmosphere (air) on the Enterprise and the vacuum (space) outside. Similarly, in the plasma window, a plasma (which is an ionized gas confined by electric and magnetic fields) separates air from a vacuum by preventing the air from rushing into the vacuum. A variety of gases can be used to operate this window. When argon is used, the window color is blue, similar to that shown in Star Trek.