LHAASO-WCDA++ Photoelectron Multiplier Tube Optimal Design Of Voltage Divider Circuit

The various information to be measured by the cosmic ray acceleration source carried by high energy gamma photons is an important probe for the study of the origin of the cosmic ray,so it is also known as the"messenger"particle of the cosmic ray source.After nearly 50years of exploration,physicists have gradually opened up a new observation window for very high energy gamma.This observation window has greatly enriched our cognition of high-energy phenomena in the universe.At present,Fermi satellite detector has discovered more than 3000 gamma ray source above 100MeV.In the higher energy region,the ground^based Cerenkov telescope and EAS array has also observed more than 100 gamma ray sources above 100GeV.The Large High Altitude Air Shower Observatory(“LHAASO”)is the next generation of detectors put forward by Chinese scientists.The detector has the characteristics of high angle resolution,the ability to eliminate the strong background noise,and also has the ability of al-weather all sky survey in large field.All these characteristics make its very high-energy Sky Patrol sensitivity and ultra high energy sensitivity hold the leading position in the world.The core goal of LHAASO is to explore the origin of high-energy cosmic rays and interrelated cosmic evolution,high-energy astrological evolution and new physics frontiers.By scanning the gamma ray sources in the whole day region and measuring gamma spectrum accurately,the detector accumulates the statistical samples of various gamma sources to determine the position of the"knee",so as to complete the continuous and consistent measurement of the cosmic ray energy spectrum,realize the seamless connection between the direct measurement of space line and the air cluster on the ground,and then develop the new physics research frontiers,such as dark matter.LHAASO is divided into three parts:the ground shower particle array(KM2A)with an area of 1 km~2which is composed of 5635electronic detectors and 1221 muon detectors,the 78000 m~2 water Cherenkov detector array(WCDA),and the wide angle Cherenkov telescope array(WFCTA)composed of 12 wide angle Cerenkov telescopes.As an important component of LHAASO,WCDA has the characteristics of all-weather operation,carrying more accurate time information and high resolution.Measuring the core position and the distribution information of particle number in LHAASO-WCDA can help us to identify particle and realize precision measurement of energy spectrum of the higher energy cosmic ray.In order to measure information of the particles near the core of primary cosmic ray between 100 TeV and 10 PeV and to distinguish them,a dynamic extension system called WCDA++is proposed.This sysytem is implemented by placing a small PMT of 1.5 inches next to PMT of 8 inches in each detection unit.The distance between large and small PMT is220mm.This paper is aimed at the research on the design ofvoltage divider of the 1.5inches PMT,including selection of photomultiplier,optimum design of voltage division ratio,test of PMT characteristic parameters and batch test of thevoltage divider designed for the selected photomultiplier.