Measuring the optical parameters for LHAASO-MD

Abstract The Large High Altitude Air Shower Observatory (LHAASO) is a hybrid detector array, which will be capable of surveying the north VHE gamma-ray sky from 100 GeV to 1 PeV. The muon detector is a kind of water Cherenkov detector; thus, its optical properties are crucial for construction and understanding of the detector. We designed a series of methods to measure the optical parameters of water and inner layer, and the results from different methods are consistent with each other, which proves the reliability of the measurement results and provides an improved understanding of the detector.