Particle beam
A particle beam is an accelerated stream of atoms or subatomic particles (often moving at very near the speed of light) directed by magnets and focused by electrostatic lenses.
Subatomic particles as electrons, positrons, and protons can be accelerated to high velocities and energies, usually expressed in terms of center-of-mass energy, by machines that impart energy to the particles in small stages or nudges, ultimately achieving in this way very high energy particle beams, measured in terms of billions and even trillions of electron volts. Thus, in terms of their scale, particles can be made to perform as powerful missiles for bombarding other particles in a target substance or for colliding with each other as they assume intersecting orbits.
A charged particle is drawn forward by a magnetic field with a charge the opposite of the particle (like charges repel one another, opposites attract); as the particle passes through a series of magnetic fields in sequence, each accelerates it until the charged particle is moving at a high speed. A natural analogy to particle beams is lightning, where electrons flow from negatively charged clouds to positively charged clouds or the earth.
Particle beams as weapons
Though particle beams are perhaps most famously employed as weapon systems in science fiction, the U.S. Advanced Research Projects Agency started work on particle beam weapons as early as 1958 [1], two years before the first scientific demonstration of Lasers. The general idea of particle-beam weaponry is to hit a target object with a stream of accelerated particles moving at near the speed of light and therefore carrying tremendous kinetic energy; the particles transfer their kinetic energy to the atoms in the molecules of the target upon striking, much as a cue ball transfers its energy to the racked balls in billiards, thus exciting the target's atoms and superheating the target object in such a short time that it explodes. Currently, the materials for such weapons are "high-risk" and may not be developed for some time. [2].
Particle cannons are not likely to be used in a near future conflict as the power needed to project such a highly powered beam surpasses the production capabilities of any standard battlefield powerplant. This beam weapon is undoubtedly also very hard not to notice; particles travelling near the speed of light are not usually seen on a battlefield. It may be possible to use particle beams as part of the Strategic Defense Initiative (dubbed "Star Wars"), but the problem of a viable power source still stands, even more so in space. It may be possible in the future with possible fusion power, but this technology is not expected to be perfected and be in mass use for several decades. If perfected this could be a new horizon in conventional weaponry, being easily as dangerous as any kinetic weapon, and effectively making any substance it comes into contact with an explosive.
Particle weapons are often overlooked when compared to lasers, even though they have some advantages over their more well known counterpart. Because the particle beam is in fact millions of tiny projectiles, it transmits its kinetic energy to the atomic structure of the target making it difficult to protect a target from it. This obviously makes the weapon very destructive, and highly lethal to anyone it hits. However, it is easier to deflect a particle beam if one possesses powerful magnetic or electromagnetic fields, but at the speeds the beam would travel, one cannot be sure how effective these countermeasures would be. Also, the atmosphere would reduce the beam strength very quickly, because the air molecules would slow down and scatter the particles. Only actual testing will prove how effective particle beams would really be for military applications.
In Fictions
In the game Command & Conquer: Generals, Partical Cannon is used as the USA superweapon.