GAMMA

GAMMA

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GAMMA experiment is a study of: a) Primary cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 energy spectra and elemental composition
(abundances of the elements) at energies 1015-1018eV
EV
EV, eV, e. V. may refer to:* Electronvolt, a unit of energy* Eingetragener Verein, a registered voluntary association in Germany* Estonia's official name, Republic of Estonia, in Estonian: Eesti Vabariik*Everett Railroad's reporting mark...

 (so called knee energy region)
b) Galactic
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 diffuse
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

 gamma-ray intensity at energies 1014-1015eV
c) Extensive Air Showers
Air shower (physics)
An air shower is an extensive cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray enters the atmosphere...

 (EAS) at the mountain level by the ground-based EAS array and underground muon
Muon
The muon |mu]] used to represent it) is an elementary particle similar to the electron, with a unitary negative electric charge and a spin of ½. Together with the electron, the tau, and the three neutrinos, it is classified as a lepton...

 scintillation counters; d) Hard jets
Jet (particle physics)
A jet is a narrow cone of hadrons and other particles produced by the hadronization of a quark or gluon in a particle physics or heavy ion experiment. Because of QCD confinement, particles carrying a color charge, such as quarks, cannot exist in free form. Therefore they fragment into hadrons...

 production at energies ~1016eV by the muon multi-core shower events.

GAMMA experiment is deployed on the South side of Mount Aragats
Mount Aragats
Mount Aragats , Alagoz - is a large andesitic-to-dacitic stratovolcano in NW Armenia about 40 km NW of the capital city of Yerevan. It is the highest point in Armenia, located in the province of Aragatsotn, northwest from Yerevan. Located on its slopes are the Byurakan Observatory and the...

 in Armenia
Armenia
Armenia , officially the Republic of Armenia , is a landlocked mountainous country in the Caucasus region of Eurasia...

 (Cosmic-ray observatory
Cosmic-ray observatory
A cosmic-ray observatory is a scientific installation built to detect high-energy-particles coming from space called cosmic rays. This typically includes photons , electrons, protons, and some heavier nuclei, as well as antimatter particles...

). The facility consists of a ground-based extensive air shower
Air shower
Air shower can refer to the following terms:*Air shower , the shower of particles produced when a high energy cosmic ray hits an atom high in the atmosphere*Air shower , a specialized antechamber of a cleanroom...

 (EAS) array of 33 surface detection stations and 150 underground muon detectors. The elevation of the GAMMA facility is 3200 m above sea level, which corresponds to about 700 g/cm2 of atmospheric depth. The surface stations of the EAS array are arranged in 5 concentric circles of 20, 28, 50, 70 and 100 m radii, and each station contains 3 plastic scintillation detectors
Scintillator
A scintillator is a special material, which exhibits scintillation—the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e., reemit the absorbed energy in the form of light...

 with the dimensions of 1×1×0.05m3. 9 central detector stations contain an additional small scintillator with dimensions 0.3×0.3×0.05 m3 for high particle density (>>100 particles/m2) measurements. A photomultiplier
Photomultiplier
Photomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...

 tube is placed on the top of the aluminum casing covering each scintillator. One of three detectors of each station is viewed by two photomultipliers, one of which is designed for fast timing measurements. 150 underground muon detectors are compactly arranged in the underground hall under 2.3 kg/cm2 of concrete and rock providing the detection of shower muons with energy greater than 5 GeV
GEV
GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...

.

The results of GAMMA experiment for 2004-2010 runs are presented in references below.