Timing calibration of the LHAASO-KM2A electromagnetic particle detectors

Abstract

The Large High Altitude Air Shower Observatory (LHAASO) is a multipurpose project focusing on high energy gamma ray astronomy and cosmic ray physics. The 1 km2 array (KM2A) of this observatory will consist of 5242 electromagnetic particle detectors (EDs) and 1171 muon detectors (MDs). The remoteness and numerous EDs extremely demand a robust and automatic calibration procedure. In this paper, a self-calibration method which relies on the measurement of charged particles within the extensive air showers is proposed. The method is fully validated by Monte Carlo simulation and successfully applied in a KM2A prototype array experiment. The self-calibration method can be used to determine the detector time-offset constants at the subnanosecond level, which is adequate to meet the physical requirements of LHAASO experiment.