A total vacuum is theoretically possible

Plasma window - Plasma window

The Plasma window (not to be confused with a Plasma shield ) is a technology that fills a volume of space with plasma that is limited by a magnetic field. With current technology, this volume is quite small and the plasma is created as a flat plane in a cylindrical space.

Plasma is any gas whose atoms or molecules have been ionized and is a separate phase of matter. This is most often achieved by heating the gas to extremely high temperatures, although other methods exist. Plasma becomes increasingly viscous at higher temperatures, to the point that other substances have difficulty getting through.

The viscosity of a plasma window allows it to separate gas from a total vacuum at normal atmospheric pressure and has reportedly been able to withstand a pressure differential of up to nine atmospheres. At the same time, the plasma window lets radiation such as laser and electron beams through. This property is key to the usefulness of the plasma window - the technology of the plasma window enables radiation that can only be generated in a vacuum to be applied to objects in an atmosphere. Electron beam welding is a major application of plasma windows, which makes EBW useful outside of a harsh vacuum.


The plasma window was invented at Brookhaven National Laboratory by Ady Hershcovitch and patented in 1995.

Further inventions based on this principle include the plasma valve from 1996.

In 2014, a group of students at the University of Leicester published a study describing how plasma deflector shields work for spaceships.

In 2015 Boeing received a patent for a force field system to protect against shock waves from explosions. It is not intended to protect against projectiles, radiation, or energy weapons such as lasers. The field supposedly works with a combination of lasers, electricity and microwaves to quickly heat the air and create a field of (ionized) superheated air plasma that disrupts or at least attenuates the shock wave. No working models are known until March 2016.

Michio Kaku suggests force fields that consist of three layers. The first is the powerful plasma window that can vaporize incident objects, block radiation and particles. The second layer consists of thousands of laser beams arranged in a tight lattice configuration to vaporize any objects that managed to get through the laser screen through the laser beams. The third layer is an invisible but stable layer of material such as carbon nanotubes or graphene, which is only one atom thick and therefore transparent, but stronger than steel, in order to block possible deposits from destroyed objects.

Plasma valve

A related technology is the plasma valve, which was invented shortly after the plasma window. A plasma valve is a layer of gas in the shell of a particle accelerator. The ring of a particle accelerator contains a vacuum, and breaking that vacuum is usually catastrophic. However, if an accelerator equipped with plasma valve technology breaks through, the gas layer is ionized within a nanosecond, creating a seal that prevents the accelerator from recompressing. This gives technicians time to turn off the particle beam in the accelerator and slowly squeeze the accelerator ring back together to avoid damage.


The physical properties of the plasma window vary depending on the application. The original patent cited temperatures around 15,000 K (14,700 ° C; 26,500 ° F).

The only limit to the size of the plasma window is the current power constraints, as generating the window consumes about 20 kilowatts per inch (8 kW / cm) in the diameter of a round window.

The plasma window radiates brightly, the color depending on the gas used.

Similarity to "force fields"

In science fiction, like the TV series Star Trek , a fictional technology called a "known force field" is often used as a device. In some cases it is used as an external "door" for hangars on spacecraft to prevent the ship's internal atmosphere from escaping into space. Plasma windows could theoretically serve such a purpose if enough energy were available to generate them. The StarTram proposal provides for the regular, but short-term use of a high-performance MHD window over a launch tube with a diameter of several meters in order to prevent excessive vacuum loss in the moments when a mechanical closure is temporarily before a hypervelocity Spaceship opens.

See also

Other sources

  • BNL wins R&D 100 award for "Plasma Window"
  • Ady Hershcovitch. Plasma window technology for the propagation of particle beams and radiation from the vacuum into the atmosphere


  • Ady Hershcovitch (1995). High pressure arcs as a vacuum-atmosphere interface and plasma lens for non-vacuum electron beam welding machines, electron beam melting and non-vacuum ion material modification, Journal of Applied Physics , 78 (9): 5283-5288


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