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Institute of High Energy Physics ,CAS

Contact: Bai YunXiang


Email: baiyx@ihep.ac.cn

The Large High Altitude Air Shower Observatory

      he Large High Altitude Air Shower Observatory (LHAASO) is a major national infrastructure project for science and technology launched during the 12th Five-Year Plan period. It mainly aims to understand the origins of high-energy cosmic rays and conduct basic research on topics including high energy gamma-ray emission, evolution of astronomical objects, and dark matter distribution. The research facility was approved by the National Development and Reform Commission (NDRC) in December 2015, with a total investment of about 1.2 billion RMB and a construction period of 4 years. Located at about 4,410 m above sea level on Haizi Mountain in Daocheng, Sichuan Province, the facility is jointly constructed by the Chinese Academy of Sciences and the Sichuan Provincial Government.


  • KM2A-ED

          Used for measuring the secondary electro-magnetic particles in the EAS. The detecting medium is plastic scintillator. The scintillation light generated by charged particles in the scintillator is collected through wavelength shift optical fibers, conducted to photomultiplier tubes (PMTs) and converted to electrical signals for measurement.

  • KM2A-MD

          Used for measuring the muon content of the EAS. Soft water bags that contain ultrapure water are placed in a metal shell, and a PMT is installed at the top center of the water bag to collect the Cherenkov light generated in the water by muons that enter the tank. The Cherenkov light is then converted to electric signals for measurement.

  • WCDA

          A 78,000 m2 array, composed of 3 adjacent large pools (2 with an area of dimensions 150 m x150 m, 1 with dimensions of 300m x110 m), at a depth of 4.4 m. Each pool can be divided into several 5 x 5 m unit detectors, each provided with 1-2 PMTs for measuring the Cherenkov light generated in the water by secondary particles in the EAS. The Cherenkov light is then converted to electnc signals for measurement.


          measures Cherenkov light or fluorescence generated in the atmosphere by high-energy cosmic rays or high-energy gamma rays through the shower. With the help of the unique removable characteristics of a telescope, and through phased aray layout adjustment, in combination of KM2A, WCDA. muiti-parameter and energy division segment, it accurately measures the component energy spectrum of cosmic rays. A spherical reflect-ing mirror composed of multiple lenses is used, with the refectedight collected by a PMT array located in the focal plane