Performance of Laser Energy Measurement System for LHAASO-WFCTA

The Large High Altitude Air Shower Observatory (LHAASO) is located in Haizi Mountain, Daocheng County, Sichuan Province, with an average elevation of 4.410 meters. The laser calibration system is one of the components of LHAASO's Wide Angle Cerenkov Telescope Array (WFCTA), used to calibrate the absolute gain of the number of photons received by WFCTA. The laser energy measurement system in the laser calibration system consists of three parts: an energy sensor, an energy meter, and an insulation system. It is mainly used to accurately measure the energy of a pulsed laser beam emitted into the WFCTA field of view. This article mainly conducts relative calibration and performance research on the energy probe, and designs and develops an insulation system to ensure the normal operation of the energy probe in harsh high-altitude areas. The accuracy of laser energy measurement can be improved through relative calibration between energy probes. The performance test results of the energy probe indicate that the unevenness is less than 1.5% in a circular area with a diameter of 8 mm centered on the center of the energy probe. In addition, the energy probe has a strong temperature effect