The Test And Research Of PMTs In LHAASO-KM2A Project

The Large High Altitude Air Shower Observatory project (LHAASO) will build a large air shower array, which covers an area of1square kilometer with a target at exploring the origin of the cosmic rays. The main part of array is KM2A.The fundamental purpose of KM2A is the measurement of gamma ray source.The KM2A compose of more than5000ED detectors and more than1000muon detectors, The ED detector is plastic scintillator detector. The function of the plastic scintillator detectors are directly correlation with the characteristic of the PMTs, which play an important role in the detector. In order to achieve the physics target of KM2A, the detailed understand of PMTs is necessary.The laboratory for PMTs batch testing was built up in SHANDONG University with the mission of testing PMTs for KM2A, which has capability of testing16PMTs at a time. The laboratory system consists of the hardware and software parts. Up to now it is already put into use and the test results have already come out. In addition, with the purpose of sharing test results with collaborators, database based on MySQL was setup using the PHP WEB server with Apache supporting realizing query on line.Methods for PMTs testing should refer to the capability of ED detectors that apply to KM2A. There are several testing items that to be carried out, such as scan of photocathode, measurement of SPE spectrum, gain respond to the high voltage and the linearity. The select of scanning region bases on the area of128fibres together. Utilize of the intensity of light and the fit methods of data should follow the characteristics of PMTs. The choice of testing HV should within the working HV and must involve the testing HV of SPE spectrum, and so on. Considering specialization of the batch testing system, configure of parameters as well as methods adopted should proceed with PMTs on the whole, but also take solo PMT into consideration simultaneously.To guarantee the reliability of test results, experiments of calibration were carries out between two laboratories. The batch testing results in keeping with the testing results in IHEP basically through calibration.