Cherenkov radiation glowing in the core of a TRIGA reactor

Cherenkov radiation (also spelled Cerenkov or sometimes Čerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than the speed of light in that medium. The characteristic "blue glow" of nuclear reactors is due to Cherenkov radiation. It is named after Russian scientist Pavel Alekseyevich Cherenkov, the 1958 Nobel Prize winner who was the first to rigorously characterize it. Image File history File links TrigaReactorCore. ... Image File history File links TrigaReactorCore. ... TRIGA is a class of small nuclear reactor designed and manufactured by General Atomics of the USA. TRIGA is an acronym of Training, Research, Isotopes, General Atomics. This type of reactor can be installed without a containment building, and is designed for use by scientific institutions and universities for purposes... Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... Particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... // Definition An Insulator is a material or object which resists the flow of electric charge. ... Speed is the rate of motion, or equivalently the rate of change of position, many times expressed as distance d moved per unit of time t. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... Core of a small nuclear reactor used for research. ... Pavel Alekseyevich Cherenkov (Russian Павел Алексеевич Черенков) (July 28, 1904 - January 6, 1990) was a Soviet physicist and Nobel Prize winner. ... 1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ... Hannes Alfvén (1908–1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ...

Physical origin

While relativity holds that the speed of light in a vacuum is a universal constant (c), the speed of light in a material may be significantly less than c. For example, the speed of light in water is only 0.75c. Matter can be accelerated beyond this speed during nuclear reactions and in particle accelerators. Cherenkov radiation results when a charged particle, most commonly an electron, exceeds the speed of light in a dielectric (electrically insulating) medium through which it passes. The special theory of relativity was proposed in 1905 by Albert Einstein in his article On the Electrodynamics of Moving Bodies. Some three centuries earlier, Galileos principle of relativity had stated that all uniform motion was relative, and that there was no absolute and well-defined state of rest... Look up Vacuum in Wiktionary, the free dictionary. ... In science, a physical constant is a physical quantity whose numerical value does not change. ... Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ... In physics, matter is commonly defined as the substance of which physical objects are composed, not counting the contribution of various energy or force-fields, which are not usually considered to be matter per se (though they may contribute to the mass of objects). ... A 1960s single stage 2 MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric fields to propel electrically charged particles to high speeds and magnetic fields to contain them. ... The Electron is a fundamental subatomic particle that carries an electric charge. ... A dielectric, or electrical insulator, is a substance that is highly resistant to electric current. ...

Moreover, the velocity of light that must be exceeded is the phase velocity rather than the group velocity. The phase velocity can be altered dramatically by employing a periodic medium, and in that case one can even achieve Cherenkov radiation with no minimum particle velocity — a phenomenon known as the Smith-Purcell effect. In a more complex periodic medium, such as a photonic crystal, one can also obtain a variety of other anomalous Cherenkov effects, such as radiation in a backwards direction (whereas ordinary Cherenkov radiation forms an acute angle with the particle velocity). The phase velocity of a wave is the rate at which the phase of the wave propagates in space. ... The group velocity of a wave is the velocity with which the variations in the shape of the waves amplitude (known as the modulation or envelope of the wave) propagate through space. ... The Smith-Purcell effect was the precursor of the free electron laser (FEL). ... The opal in this bracelet contains a natural periodic microstructure responsible for its iridescent color. ...

As a charged particle travels, it disrupts the local electromagnetic field (EM) in its medium. Electrons in the atoms of the medium will be displaced and polarized by the passing EM field of a charged particle. Photons are emitted as an insulator's electrons restore themselves to equilibrium after the disruption has passed. (In a conductor, the EM disruption can be restored without emitting a photon.) In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, when the disruption travels faster than the photons themselves travel, the photons constructively interfere and intensify the observed radiation. This article or section may be confusing or unclear for some readers, and should be edited to rectify this. ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle of a chemical element that retains its chemical properties. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... Look up equilibrium in Wiktionary, the free dictionary. ... In science and engineering, conductors are materials that contain movable charges of electricity. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...

The geometry of the Cherenkov radiation.

A common analogy is the sonic boom of a supersonic aircraft or bullet. The sound waves generated by the supersonic body do not move fast enough to get out of the way of the body itself. Hence, the waves "stack up" and form a shock front. Similarly, a speed boat generates a large bow shock because it travels faster than waves can move on the surface of the water. Image File history File links Cherenkov. ... Image File history File links Cherenkov. ... It has been suggested that this article or section be merged into sound barrier. ... It has been suggested that hypersonic be merged into this article or section. ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... Introduction The shock wave is one of several different ways in which a gas in a supersonic flow can be compressed. ...

In the same way, a superluminal charged particle generates a photonic shockwave as it travels through an insulator.

In the figure, v is the velocity of the particle (red arrow), β is v/c, n is the refractive index of the medium. The blue arrows are photons. So: The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ...

Characteristics

Intuitively, the overall intensity of Cherenkov radiation is proportional to the velocity of the inciting charged particle and to the number of such particles. Unlike fluorescence or emission spectra that have characteristic spectral peaks, Cherenkov radiation is continuous. The relative intensity of one frequency is proportional to the frequency. That is, higher frequencies (shorter wavelengths) are more intense in Cherenkov radiation. This is why visible Cherenkov radiation is observed to be brilliant blue. In fact, most Cherenkov radiation is in the ultraviolet spectrum - it is only with sufficiently accelerated charges that it even becomes visible; the sensitivity of the human eye peaks at green, and is very low in the violet portion of the spectrum. Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... In optics, stimulated emission is the process by which, when perturbed by a photon, matter may lose energy resulting in the creation of another photon. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... The wavelength is the distance between repeating units of a wave pattern. ... Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. ...

There is a cut-off frequency for which the equation above cannot be satisfied. Since the refractive index is a function of frequency (and hence wavelength), the intensity doesn't continue increasing at ever shorter wavelengths even for ultra-relativistic particles (where v/c approaches 1). At X-Ray frequencies, the refractive index becomes less than unity and hence no X-Ray emission (or shorter wavelength emissions such as gamma rays) would be observed. However, X-rays can be generated at special energies corresponding to core electronic transitions in a material, as the index of refraction is often greater than 1 at these energies. The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ...

As in sonic booms and bow shocks, the angle of the shock cone is inversely related to the velocity of the disruption. Hence, observed angles of incidence can be used to compute the direction and speed of a Cherenkov radiation-producing charge. This article needs to be cleaned up to conform to a higher standard of quality. ...

Uses

Cherenkov radiation is used to detect high-energy charged particles. In pool-type nuclear reactors, the intensity of Cherenkov radiation is related to the frequency of the fission events that produce high-energy electrons, and hence is a measure of the intensity of the reaction. Cherenkov radiation is also used to characterize the remaining radioactivity of spent fuel rods. Pool-type reactors are a type of nuclear reactor that has a core immersed in an open pool of water. ... For the generation of electrical power by fission, see Nuclear power plant An induced nuclear fission event. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ...

When a high-energy cosmic ray interacts with the Earth's atmosphere, it may produce an electron-positron pair with enormous velocities. The Cherenkov radiation from these charged particles is used to determine the source and intensity of the cosmic ray, which is used for example in the Imaging Atmospheric Cherenkov Technique (IACT), by experiments such as VERITAS, H.E.S.S., and MAGIC. Similar methods are used in very large neutrino detectors, such as the Super-Kamiokande, the Sudbury Neutrino Observatory (SNO) and IceCube. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Layers of Atmosphere (NOAA) Air redirects here. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon (or neutral bosonic fields). ... For closer details about Imaging Air Cherenkov Telescopes see MAGIC Homepage: http://magic. ... The IACT or Imaging Atmospheric Cherenkov Technique is the method wherby very high energy gamma-ray photons in the 50GeV to 50TeV range can be detected by ground based telescopes. ... In Roman mythology, Veritas (truth) was the goddess of truth and a daughter of Saturn. ... CT2 and CT3 telescopes All four telescopes in operation at night High Energy Stereoscopic System or H.E.S.S. is a next-generation system of Imaging Atmospheric Cherenkov telescopes for the investigation of cosmic gamma rays in the 100 GeV and TeV energy range. ... MAGIC is the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope. ... The neutrino is an elementary particle. ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Artists concept of SNOs detector. ... The IceCube Neutrino Detector is a neutrino telescope currently under construction at the South Pole. ...

Cherenkov radiation can also be used to determine properties of high-energy astronomical objects that emit gamma rays, such as supernova remnants and blazars. This is done by projects such as STACEE, a gamma ray detector in New Mexico. The Crab Nebula is an expanding cloud of gas created by the 1054 supernova. ... A blazar is a galaxy with a very compact and highly variable energy source at the center of the host galaxy. ... STACEE, the Solar Tower Atmospheric Cherenkov Effect Experiment, is a gamma ray detector located near Alberquerque, New Mexico. ... Capital Santa Fe Largest city Albuquerque Area  Ranked 5th  - Total 121,665 sq mi (315,194 km²)  - Width 342 miles (550 km)  - Length 370 miles (595 km)  - % water 0. ...

A very common use of Cherenkov radiation are RICH detectors, which are used for particle identification. RICH stands for Ring imaging Cherenkov detector. In a RICH detector a cone of Cherenkov light is produced when a high speed particle traverses a suitable medium, often called radiator. This light cone is detected on a position sensitive planar photon detector, which allows reconstructing a ring or disc, the radius of which is a measure for the Cherenkov emission angle. Both focusing and proximity-focusing detectors are in use. In a focusing RICH detector the photons are collected by a spherical mirror and focused onto the photon detector placed at the focal plane. The result is a circle with a radius independent of the emission point along the particle track. This scheme is suitable for low refractive index radiators, i.e. gases, due to the larger radiator length needed to create enough photons. In the more compact proximity-focusing design a thin radiator volume emits a cone of Cherenkov light which traverses a small distance - the proximity gap - and is detected on the photon detector plane. The image is a ring of light the radius of which is defined by the Cherenkov emission angle and the proximity gap. The ring thickness is determined by the thickness of the radiator. An example of a proximity gap RICH detector is the High Momentum Particle IDentification (HMPID), a detector currently under construction for ALICE (A Large Ion Collider Experiment), one of the six experiments at the LHC (Large Hadron Collider) at CERN. A Ring Imaging Cherenkov detector (RICH detector) is a particle detector that can determine the velocity, , of a fundamental particle. ... ALICE (A Large Ion Collider Experiment) is one of the five detector experiments (ALICE, ATLAS, CMS, TOTEM, and LHCb) being constructed at the Large Hadron Collider at CERN. It is optimized to study heavy ion collisions. ... The Large Hadron Collider (LHC) is a particle accelerator and collider located at CERN, near Geneva, Switzerland ( ). Currently under construction, the LHC is scheduled to start operation in November 2007, when it will become the worlds largest and highest energy particle accelerator. ... CERN logo The Organisation Européenne pour la Recherche Nucléaire (English: European Organization for Nuclear Research), commonly known as CERN, pronounced (or in French), is the worlds largest particle physics laboratory, situated just west of Geneva on the border between France and Switzerland. ...

See also

• Bremsstrahlung
• List of light sources
• Frank-Tamm formula

(help· info), (from the German bremsen, to brake and Strahlung, radiation, thus, braking radiation), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. ... This page is a list of sources of light. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

References

• L. D. Landau, E. M. Liftshitz, and L. P. Pitaevskii, Electrodynamics of Continuous Media (Pergamon: New York, 1984).
• J. V. Jelley, Cerenkov Radiation and Its Applications (Pergamon: London, 1958).
• S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953).
• Chiyan Luo, Mihai Ibanescu, Steven G. Johnson, and J. D. Joannopoulos, "Cerenkov Radiation in Photonic Crystals," Science 299, 368–371 (2003).