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{{Infobox research project
| name = The GRAPES-3 experiment
| title =
| image = Air shower detector array of GRAPES-3 experiment.jpg
| image_alt = GRAPES-3 Air Shower Array
| caption = GRAPES-3 Air Shower Array
| keywords =
| project_type =
| funding_agency =
| sponsors =
| framework_programme =
| project_reference =
| research_objective =
| location = [[Ooty]], India
| coordinator = 
| participants = [[Tata Institute of Fundamental Research]], [[Osaka City University]], [[Nagoya Women's University]].
| partners =
| budget =
| funding =
| start = 1955
| end =
| website = {{url|http://alpha.sci.osaka-cu.ac.jp/grapes3/index.html}}
}}
{{For|the similarly named computer|GRAPE-3}}
{{morefootnotes|date=August 2020}}
{{Use dmy dates|date=August 2020}}
{{Use Indian English|date=August 2020}}
The '''GRAPES-3 experiment''' (or '''Gamma Ray Astronomy PeV EnergieS phase-3''') located at [[Ooty]] in India started as a collaboration of the Indian [[Tata Institute of Fundamental Research]] and the Japanese [[Osaka City University]], and now also includes the Japanese [[Nagoya Women's University]].

GRAPES-3 is designed to study [[cosmic ray]]s with an array of [[air shower (physics)|air shower]] [[detector]]s and a large area [[muon]] detector. It aims to probe acceleration of cosmic rays in the following four astrophysical settings. These include acceleration of particles to, (i) ~100 MeV in [[atmosphere|atmospheric]] [[electric field]]s through muons, (ii) ~10 GeV in the [[Solar System]] through muons, (iii) ~1 PeV in [[Milky Way|our galaxy]], (iv) ~100 EeV in the nearby universe through measurement of diffuse [[gamma ray]] flux.

The GRAPES-3 is located at N11.4o, E76.7o, 2200m above mean sea level. The observations began with 217 plastic [[scintillator]]s and a 560 m2 area muon detector in 2000. The scintillators detect [[charged particle]]s contained in extensive air showers produced by interaction of high energy cosmic rays in the atmosphere. At present the array is operating with ~400 scintillators that are spread over an area of 25,000 m2. The energy threshold of muon detectors is 1 GeV.

==Objectives==
Study of
# The origin, acceleration and propagation of >1014 eV cosmic rays in the galaxy and beyond.
# Existence of "Knee" in the energy spectrum of cosmic rays.
# Production and/or acceleration of highest energy (~1020 eV) cosmic rays in the universe.
# Astronomy of multi-TeV γ-rays from neutron stars and other compact object.
# Sun the closest astrophysical object, accelerator of energetic particles and its effects on the Earth.

==Overview==
The first cosmic ray experiment was started in 1955 by [[B. V. Sreekantan]] by setting up [[cloud chamber]]s that heralded the beginning of research at the [[Cosmic Ray Laboratory]] (CRL) in Ooty.{{citation needed|date=February 2017}} The next decade witnessed a variety of experiments involving high energy interactions and extensive air shower studies in this laboratory. The world's largest multiplate cloud chamber was operated here{{citation needed|date=February 2017}} as part of an air shower array and significant results{{which|date=February 2017}} on the high energy nuclear interactions and cores of extensive air showers were obtained. A triple set-up comprising an air [[Cerenkov radiation|Cherenkov]] counter, a multiplate cloud chamber and a total absorption spectrometer was operated in the early seventies to study the differences in the characteristics of interactions with nuclei of protons and pions in the energy range 10-40 GeV.{{citation needed|date=February 2017}} This enabled the time structure study of nuclear active components of air showers and led to the discovery that the nucleon-anti-nucleon production cross-section considerably increases with energy.{{citation needed|date=February 2017}}

In continuation of the work on cosmic ray research at CRL, GRAPES-1 experiment was upgraded in various stages to GRAPES-2. However, due to the technical and administrative problem in its further expansion, a new experiment was set up at the RAC{{clarify|date=February 2017}} site 8 km from the old site which is called GRAPES-3. The GRAPES-3 experiment at present is operating with ~400 (each 1 m2) plastic scintillator detectors with a separation of 8 meters, to record the density and arrival time of particles in cosmic ray showers, and in continuous operation.{{citation needed|date=February 2017}} At present, GRAPES-3 array is the highest density conventional EAS array in the world,{{citation needed|date=February 2017}} and also, this experiment associated with a huge 560 m2 area tracking muon detector, is also the largest area tracking detector anywhere.{{citation needed|date=February 2017}}

==Results==
Several results have recently been obtained from the GRAPES-3 experiment on a variety of topics, a few of which are listed below.
* Measurement of primary composition in the energy 50 TeV - 1 PeV overlapping with direct measurements{{citation needed|date=February 2017}}
* Precision measurements of Forbush decrease events including rigidity dependence of its amplitude{{citation needed|date=February 2017}}
* Measurement of turbulent magnetic field in the shock-sheath region in the Coronal mass ejections (CMEs) by using multi-rigidity muon data{{citation needed|date=February 2017}}
* Precision measurement of the solar diurnal anisotropy and its higher harmonics including its rigidity dependence{{citation needed|date=February 2017}}
* Precision measurement of the density gradient of cosmic rays in the solar system by probing Swinson flow{{citation needed|date=February 2017}}
* Precision measurement of the anti-correlation between changes in solar wind velocity and cosmic ray intensity{{citation needed|date=February 2017}}
* Measurement of the electrical potential, size and height of a thundercloud, which broke the existing record. <ref>{{cite news |last1=Desikan |first1=Shubashree |title=Ooty's muon detection facility measures potential of thundercloud |url=https://www.thehindu.com/sci-tech/science/ootys-muon-detection-facility-measures-potential-of-thundercloud/article26619932.ece |access-date=24 March 2019 |agency=The Hindu}}</ref>

==References==

{{Reflist}}

==Publications==

* {{cite journal
|last1=Hariharan |first1=B.
|display-authors=etal
|year=2019
|title=Measurement of the Electrical Properties of a Thundercloud Through Muon Imaging by the GRAPES-3 Experiment
|journal=[[Physical Review Letters]]
|volume=122 |issue=10 |page= 105101
|bibcode=
|doi=10.1103/PhysRevLett.122.105101
|pmid=30932668
|arxiv=1903.09801
|s2cid=85500186
}}
* {{cite journal
|last1=Mohanty |first1=P. K.
|display-authors=etal
|year=2016
|title=Transient weakening of Earth's magnetic shield probed by a cosmic ray burst
|journal=[[Physical Review Letters]]
|volume=117 |issue=17 |page=171101
|bibcode=
|doi=10.1103/PhysRevLett.117.171101
|pmid=27824449
|url=https://zenodo.org/record/896243}}
* [https://www.bbc.com/news/world-asia-india-39100109 "How India uses recycled pipes to detect ferocious solar storms"] — BBC News article, 1.03.2017

==External links==
* [http://grapes-3.tifr.res.in Homepage]
* [http://alpha.sci.osaka-cu.ac.jp/grapes3/index.html GRAPES-3]

{{DEFAULTSORT:Grapes-3}}
[[Category:Cosmic-ray experiments]]
[[Category:Research projects]]
[[Category:Science and technology in Tamil Nadu]]

GRAPES-3 - Revision history

>H0n0r: moved image etc. into infobox