LHAASO

LHAASO, the Large High Altitude Air Shower Observatory, is a multi-component gamma-ray and cosmic-ray observatory located in Sichuan Province, China, near Daocheng. It sits at an elevation of about 4,410 meters above sea level, a high-altitude site chosen to lower the energy threshold for detecting extensive air showers produced by high-energy particles and to improve sensitivity to very high energy gamma rays and cosmic rays.

The facility comprises several sub-detectors designed to sample different components of air showers. The KM2A is a kilometer-scale surface detector array that records charged particles and photons from showers. The WCDA, or Water Cherenkov Detector Array, uses large water-filled tanks instrumented with photomultiplier tubes to detect Cherenkov light from shower particles. A muon detector system, deployed underground, helps identify muons to distinguish gamma-ray–initiated showers from hadronic cosmic-ray events.

LHAASO aims to survey the northern sky for very-high-energy gamma rays from roughly 100 GeV to beyond 100 TeV, search for Galactic PeVatrons (sources capable of accelerating particles to PeV energies), study diffuse gamma-ray emission, and advance understanding of cosmic-ray origin, acceleration, and propagation. The project also contributes to multi-messenger astronomy and complements space-based telescopes and other ground-based facilities.

Construction and operation have progressed through the 2010s and early 2020s, with key components brought online and producing results. Notable findings include detections of gamma-ray sources at energies well into the TeV range and evidence supporting the existence of Galactic accelerators capable of reaching PeV energies. The collaboration is led by the Chinese Academy of Sciences, with participation from multiple Chinese institutions and international partners.