Huihai He

Timing calibration of the LHAASO-KM2A electromagnetic particle detectors

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.

Study of Solar Gamma Rays basing on Geant4 code

The solar gamma-ray are mainly produced by the hadronic interactions of cosmic rays with the solar atmosphere. Some theoretical works have been done to estimate the flux distribution of solar gamma-ray by Monte Carlo simulation based. In this work, we will estimate the solar gamma-ray emission based on Geant4 code. An approximate structure of the Sun and its atmosphere areconstructed in the code. The cosmic rays are generated at 600km above the solar surface. The gamma-ray are traced until they are absorbed or escape from the solar atmosphere. Finally, the flux and spectrum for observers on Earth are presented. Some comparison between our result and others are also discussed.

The dynamic range extension system for the LHAASO-WCDA experiment

The Large High Altitude Air Shower Observatory (LHAASO) will be constructed at Mountain Haizi, in Sichuan Province, China (4410m a.s.l.). The Water Cherenkov Detector Array (WCDA), one of the major component of the LHAASO, will focus on surveying the northern sky for gamma ray sources from 100 GeV to 30 TeV. The whole WCDA, owing an area of 78,000 m^{2}, is subdividing into 3120 detector cells (5×5 m^{2} each, with a water depth of 4m). Every cell has an 8 or 9-in PMT residing at the bottom to collect Cherenkov lights produced by the charged secondary particles of air showers. To observe high-energy shower events, especially to measure precisely the shower cores of events at the energy range from 100 TeV to 10 PeV for an analysis of the cosmic ray spectrum, as a dynamic range extension system, another sets of small PMTs (1-2 inch) will be added to 900 cells of the WCDA array. In this talk, the design and status of this dynamic range extension system is presented.

Calibration and monitoring of LHAASO-KM2A muon detectors with muon decay events

The Large High Altitude Air Shower Observatory (LHAASO) will be constructed at 4400 m asl in Daocheng, Sichuan Province, with the aim of discovering sources of ultra-high energy cosmic rays and studying cosmic ray physics. The whole array includes 1171 muon detectors (MDs), constituting the largest muon detector array in the world. The special high altitude and wide-field environment requires simple and stable calibration as well as monitoring method of MDs. In this paper, the muon decay events will be selected for calibrating the charge and monitoring the water level of each MD. In the prototype muon detector, the simulation and experiment results reveal that the charge of the decay electron is approximately 0.147 times that of the vertical equivalent muon for a standard MD, and the QVEM/Qe shows a linear correlation with the water level.

Timing Calibration of the LHAASO-KM2A Electromagnetic Particle Detectors Using Charged Particles Within the Extensive Air Showers

The Large High Altitude Air Shower Observatory (LHAASO) is a new generation extensive air shower (EAS) experiment focusing on high energy gamma ray astronomy and cosmic ray physics. In the LHAASO, 5242 electromagnetic particle detectors (EDs) and 1171 muon detectors (MDs), which cover an area of 1.3 km(^{2}), are designed to measure the number density and arrival time of EAS secondary particles. The remoteness and numerous detectors extremely demand a robust, automatic calibration method. In this work, a self-calibration method which uses charged particles within the EASs as the calibration beam is developed. The method is implemented in the Monte Carlo simulation and initially applied in a prototype array experiment, from which the precision and efficiency are estimated.

Study of Water Cherenkov muon detector parameters and performances for LHAASO

In the Large High Altitude Air Shower Observatory project, about 1146 water Cherenkov muon detectors will be built to discriminate cosmic ray species. Each muon detector has a 6.8 m diameter Tyvek bag containing 1.2 m height pure water in it. In the summer of 2014, a water Cherenkov muon detectors prototype was installed at YBJ, both data analysis and simulation has been performed. The detector performances strongly depend on detector parameters, especially the Tyvek reflectivity and water attenuation length. MD prototype signals are simulated by using Geant4 with different parameters, while the detector parameters are determined by comparing simulation to data. The MD performances, such as NPE and the relationship of effective attenuation length with water absorption length, Tyvek reflectivity and time ranges are studied.