Design of the LHAASO detectors



   The Large High Altitude Air Shower Observatory plans to build a hybrid extensive air shower array with an area of about 1 km\(^2\) at an altitude of 4,410 m a.s.l. in Sichuan province, China, to explore the origin of high-energy cosmic rays.


   LHAASO-KM2A will detect gamma ray sources with a sensitivity of about 1% Crab Unit at 100 TeV. It covers an area of 1 km\(^2\) with a total of 5195 scintillation detectors. Its angular resolution reaches about 0.3 degrees, and the energy resolution is better than 25%. With the help of 1171 muon detectors, cosmic nuclei background will be rejected to a level of 10-4 at 50 TeV. The design and performances of the scintillation detectors and muon detectors are described in detail.


   LHAASO-WCDA focuses on surveying the northern sky for steady and transient sources from 100 GeV to 20 TeV, with a very high background rejection power and a good angular resolution. The WCDA consists of three water ponds with a total area of 78,000 m\(^2\), and the effective water depth is 4 m. Each water pond is divided into 5m  \(\times \)  5m cells partitioned by black plastic curtains to prevent penetration of the light from neighboring cells. An 8-inch PMT sits at the bottom center of each cell, looking upward to collect Cherenkov light generated by shower secondary particles in water.


   LHAASO-WFCTA is composed of 12 wide-field-of-view Cherenkov/fluorescence telescopes. Each telescope consists of a spherical light collector of about 4.7 m\(^2\) and focal plane camera of 32  \(\times \)  32 pixels with a pixel size of 0.5 degree.

LHAASO prototype arrays

   A prototype array about 1% of LHAASO has been constructed at Yangbajing Cosmic Ray Observatory and has been in operation for more than 2 years. Its performance fully meets the design requirements.


   The LHAASO detectors are designed to fulfill the physical goals in gamma ray astronomy and cosmic ray physics. One-fourth of LHAASO will be constructed and put into operation to produce physical data by the end of 2018. The whole array will be finished in the beginning of 2021.

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This work is supported in China by NSFC (Nos. 11205165, 11375210, 11375224, 11405181, 11475190 and 11635011), the Chinese Academy of Sciences, Institute of High Energy Physics, the Key Laboratory of Particle Astrophysics, CAS.

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Correspondence to Huihai He.

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He, H., For the LHAASO Collaboration. Design of the LHAASO detectors. Radiat Detect Technol Methods 2, 7 (2018).

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  • Origin of cosmic rays
  • Gamma ray astronomy
  • Extensive air shower