Particle beam
A particle beam is a stream of charged
Charged particle
In physics, a charged particle is a particle with an electric charge. It may be either a subatomic particle or an ion. A collection of charged particles, or even a gas containing a proportion of charged particles, is called a plasma, which is called the fourth state of matter because its...

 or neutral particle
Neutral particle
In physics, a neutral particle is a particle with no electric charge. This is not to be confused with a real neutral particle, a neutral particle that is also identical to its own antiparticle.-Stable or long-lived neutral particles:...

s (often moving at very near the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

) which may be directed by magnets and focused by electrostatic lens
Electrostatic lens
An electrostatic lens is a device that assists in the transport of charged particles. For instance, it can guide electrons emitted from a sample to an electron analyzer, analogous to the way an optical lens assists in the transport of light in an optical instrument. The recent development of...

es, although they may also be self-focusing (see Pinch
Pinch (plasma physics)
A pinch is the compression of an electrically conducting filament by magnetic forces. The conductor is usually a plasma, but could also be a solid or liquid metal...


Subatomic particles such as electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s, positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...

s, and proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s 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, ultimately achieving very high energy particle beams, measured in terms of billions and even trillions of electron volts
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

. 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.

High energy beams are created in particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

s, in which a charged particle is drawn forward by an electrostatic (not magnetic) field with a charge opposite to the particle (like charges repel one another, opposites attract); as the particle passes the source of each field, the charge of the field is reversed so that the particle is now pushed on to another field source. Through a series of fields in sequence, the particle accelerates until it is moving at a high speed. A natural analogy to particle beams is lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...

, where electrons flow from negatively charged clouds to positively charged clouds or the earth.

Low and medium energy beams are quite common. Traditional cathode-ray tube televisions and computer displays use them to scan out each image, and some radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

 methods use them to treat cancer.

As weapons

Though particle beams are perhaps most famously employed as weapon systems in science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

, the U.S. Advanced Research Projects Agency
Defense Advanced Research Projects Agency
The Defense Advanced Research Projects Agency is an agency of the United States Department of Defense responsible for the development of new technology for use by the military...

 started work on particle beam weapon
Particle beam weapon
A particle beam weapon uses an ultra-high-energy beam of atoms or electrons to damage a material target by hitting it, and thus disrupting its atomic and molecular structure. A particle beam weapon is a type of directed-energy weapon, which directs energy in a particular direction by a means of...

s as early as 1958
, two years before the first scientific demonstration of laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

s. 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
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...

; 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
Cue sports , also known as billiard sports, are a wide variety of games of skill generally played with a cue stick which is used to strike billiard balls, moving them around a cloth-covered billiards table bounded by rubber .Historically, the umbrella term was billiards...

, thus exciting the target's atoms and superheating the target object in a short time, leading to explosion either of the surface layer or the interior of the target. Currently, the materials for such weapons are "high-risk" and may not be developed for some time.

The power needed to project a high-powered beam of this kind surpasses the production capabilities of any standard battlefield powerplant, thus such weapons are not anticipated to be produced in the foreseeable future. Particle beams could possibly be used from fixed locations, or in space, for example as part of the Strategic Defense Initiative
Strategic Defense Initiative
The Strategic Defense Initiative was proposed by U.S. President Ronald Reagan on March 23, 1983 to use ground and space-based systems to protect the United States from attack by strategic nuclear ballistic missiles. The initiative focused on strategic defense rather than the prior strategic...

 (dubbed "Star Wars") or similar initiatives, but the problems related to power source still stand at present, pending future development in that field.

See also

  • Beamline
    In particle physics, a beamline is the line in a linear accelerator along which a beam of particles travels. It may also refer to the line of travel within a bending section such as a storage ring or cyclotron, or an external beam extracted from a cyclic accelerator.In materials science, physics,...

  • Charged particle beam
    Charged particle beam
    A charged particle beam is a spatially localized group of electrically charged particles that have approximately the same velocity . The kinetic energies of the particles are typically measured in keV or MeV, much larger than the energies of particles at ambient temperature...

  • Electron beam
  • Ion beam
    Ion beam
    An ion beam is a type of charged particle beam consisting of ions. Ion beams have many uses in electronics manufacturing and other industries. A variety of ion beam sources exist, some derived from the mercury vapor thrusters developed by NASA in the 1960s.-Ion beam etching or sputtering:One type...

  • Linear particle accelerator
    Linear particle accelerator
    A linear particle accelerator is a type of particle accelerator that greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beamline; this method of particle acceleration was invented...

  • Microbeam
    A microbeam is a narrow beam of radiation, of micrometer or sub-micrometer dimensions. Together with integrated imaging techniques, microbeams allow precisely defined quantities of damage to be introduced at precisely defined locations...

  • Particle accelerator
    Particle accelerator
    A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

  • Directed-energy weapon
    Directed-energy weapon
    A directed-energy weapon emits energy in an aimed direction without the means of a projectile. It transfers energy to a target for a desired effect. Intended effects may be non-lethal or lethal...

  • Large Hadron Collider
    Large Hadron Collider
    The Large Hadron Collider is the world's largest and highest-energy particle accelerator. It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature....

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