Plasma Gun

Two years ago we had an article on the intricacies of “railgun” in the reflex magazine, this year let us look into the details of another weapon used in Quake, the Plasma Gun.

Plasma rifles are weapons often used in science fiction. They are, in effect, a type of raygun. Plasma weapons use a small nuclear reactor or fuel cell or other type of advanced energy storage device to power an electromagnetic accelerator that fires a stream or pulse or toroid of plasma (i.e. very energetic excited matter); real-world conventional firearms launch a metal projectile from a barrel using an expanding gas.
When fusion reactors exist, one potential source of weapons-grade plasma sources might be a direct tap on a fusion reactor, especially a dense plasma focus, since the natural yield of such a reactor is a hot high-speed plasma beam.
As well as rifles, several science fiction universes also contain pistol-scale or cannon-scale plasma-firing weapons.
Real tools that plasma rifles should not be confused with
• Plasma torches, which have existed for some years, and project plasma streams a foot at most, and are used to cut metal and concrete.
• The plasma gun as used in plasma physics.
The possibility of plasma rifles existing in the real world
At present, plasma rifles are merely theoretical, as currently they need more power than any handheld device could supply. Making real plasma weapons will need a major scientific breakthrough, as the concept of plasma-firing weapons is scientifically difficult, for various reasons:
• The technology to create plasma toroids and particle beams is presently far too bulky for anything man-portable. In such a high-performance design, the plasma would have to be stored and created in highly focused magnetic bottles, such as those used in NASA's VASIMR rocket: this design has been suggested as a potential weapon design for future real human-engineered plasma weapons. For simpler designs based on plasma cutting torches, a designer might be able to heat the plasma with an arcjet, if his power source is strong enough.
• Using current technology, if a plasma beam was fired in a planetary atmosphere, it would quickly be stopped by atmospheric resistance and would make a short hot flame like a blowtorch.
• The plasma shot out of a plasma rifle would tend to dissipate in the surrounding environment within about 50 centimeters from the gun, from thermal and/or electric pressure expansion, called blooming, unless:-
o The magnetic confinement bottle is extended all the way to the target (as it was in the games Halo: Combat Evolved and Halo 2).
o Or the particles are fired fast enough to reach a target before blooming occurs. This is then a particle beam more than a plasma beam (at least as much as any technical definition for such weapons exists). This would work in space vacuum, but in atmosphere would merely cause a hotter short flame from more violent collision between the flying particles and the atmosphere.
• One virtually universal characteristic of plasma weaponry is its tendency to overheat, thus being sometimes impractical even within the context of science fiction.