The main detector consists of a diameter transparent sphere containing 20,000 tons of linear alkylbenzene liquid scintillator, surrounded by approximately 17,000 photomultiplier tubes, a water pool, and a muon veto.
The much larger distance to the reactors (compared to less than 2 km for the Daya Bay far detector) makes the experiment better able to distinguish neutrino oscillations, but requires a much larger, and better-shielded, detector to detect a sufficient number of reactor neutrinos.