【作者】 李朝举；

【导师】 张学尧； 冯存峰；

【作者基本信息】 山东大学 ， 粒子物理与原子核物理， 2011， 硕士

【摘要】 新一代宇宙线(包括伽玛射线)实验——大型高海拔大气簇射观测站(Large High Altitude Air Shower Observatory, LHAASO)是一个平方公里级别的复合式阵列实验。为实现LHAASO科学目标,规划建设1K地面粒子阵列加上不小于4万μ探测器阵列(KM2A阵列)。KM2A是LHAASO计划的主体阵列,整个阵列由5000个电子探测器和1200个¨探测器组成。电子探测器和μ探测器均由统一的闪烁体tile拼装组成。每个tile覆以8根闪烁光纤以收集闪烁光。其中电子探测器单元包含4×4个tile,最终把光纤汇集一起耦合到一个PMT。μ探测器每个单元的闪烁光也要由一个PMT读出。因此就需要大量的PMT。根据实验需要,对PMT的放大能力,时间响应和线性等参数提出要求,因此在实验中使用之前必须要对PMT的性能参数进行测试,以确保PMT能满足实验需要,实现实验的设计目标。如此数量众多的PMT要进行测试必须要开发一套高精度,快速的测量系统。山东大学实验室建立了这样一套快速精确的PMT测试系统,该系统可以同时对16只PMT进行测试,并且高度自动化,实现了一键式操作。本文主要探讨该系统的搭建工作,从硬件组成到数据获取和数据分析等软件开发。PMT性能测试系统包括测试暗箱、光源、扫描系统、数据获取和数据库系统,测量并记录每个PMT的单光电子计数、均匀性和线性度。其中对阴极均匀性的测量是本系统最为独特的创新之处。暗箱同时安放多个PMT,采用多光源系统,由光纤把光导入PMT,对多个PMT同时测量,节约测量时间。扫描系统由精密步进电机控制,进行间距约1 mm的逐点扫描。光源由LED和激光提供,通过分光系统为多个光纤提供信号。数据获取系统基于VME系统,使用多路QDC(16路)同时获取16路PMT信号。触发信号同时作为光源驱动信号,每个PMT进行分别编号,测量结果记入数据库系统。测试系统所有的软件均基于Labview开发, Labview是一种业界领先的工业标准图形化编程工具,主要用于开发测试,测量与控制系统。它是专门为工程师和科学家而设计的直观图形化编程语言。它将软件和各种不同的测量仪器硬件及计算机集成在一起,建立虚拟仪器系统,以形成用户自定义的解决方案。实验室利用Labview提供的VISA配置串口工具实现了对BNC575信号发生器的控制,并以BNC575的多路输出可调特性协调各个子系统的工作。利用Labview提供的Datasocket函数实现了对SY1527高压电源系统的控制。利用Labview提供的VISA查找工具查找示波器资源并利用VISA读写函数实现与其通信,实现了时间特性的测试。另外,Labview自带了大量的数学工具和函数方便的实现了数据的抽取、转换、拟合和分析。测试系统搭建完成之后以对XP2012B、XP2262和R11102三只PMT的测试为例,介绍了对其放大能力、非线性和均匀性等参数的测试方法和测试结果。系统能够精确、快速的测出PMT各项参数并能长时间稳定工作。更多还原

【Abstract】 A new generation of cosmic ray(y ray included) experiment——Large High Altitude Air Shower Observatory is a compound detector array distributed in a kilometer square area. To achieve the LHAASO scientific objectives, it’s planed to build a particle array on the ground of 1Km2 area and aμdetector array no less than 40 thousand m2 area(KM2A).KM2A,the main array of LHAASO plan, is comprised of 5000 electron detectors and 1200μdetectors. Both of them are assembled with the same kind of scintillator tile covered with eight scintillating fiber to collect lights. There are four times four tiles in a electron detector. Because each detector need a PMT to measure the lights collected by fiber so we need a large number of PMTs.We must test the PMT parameters like gain, time response and linearity to ensure it match the requirements before it is used in the experiment. To test so many PMTs,we have to develop a high accuracy,fast test-system.A test-system testing 16 PMTs at one time is built up in our laboratory in Shandong university. It’s fast,accurate and intelligent,finishing everything and showing all the result for just one push. It’s the main content of this article to discuss the work that how this system is developed including hardware and software.The PMT test-system is composed of dark box, light, scanning system, data acquisition and database system. It tests and records the spe,linearity and cathode surface uniformity of each PMT.The test of uniformity of cathode surface is the largest innovation of this system.The light system is composed of LED,laser,light guide and 16 fibers transferring light to 16 PMTs. The scanning system is controlled by precise stepper motor which can be controlled by computer to sweep over point by point with 1 mm pitch. The data acquisition system is based on VME systems, making use of multiple QDC(16 Channels) for 16 PMT signals. The trigger signal at the same time is used as the light source driving signal. We number each PMT separately and record the measurement results in the database systems. All the software in test-system are developed based on Labview. Labview is an industry-leading industry-standard graphical programming tools, mainly for development and testing, measurement and control systems. It is a intuitive graphical programming language specifically designed for engineers and scientists. It establishes a virtual instrument system by integrating the software, a variety of measuring instruments and computer hardware to form a custom solution. We have the BNC575 signal generator controlled using the VISA serial configuration tool provided by Labview. Because the multi-channels of BNC575 are adjustable separately, we use the BNC575 to coordinate the various subsystems. What’s more, Datasocket functions of Labview are used to control our SY1527 high-voltage system. At the same time we use the VISA search-tool, VISA read and VISA write functions to communicate with the oscilloscope for the time-characteristics testing. In addition,Labview comes with a large number of mathematical tools and functions to facilitate the realization of the data extraction, conversion fitting and analysis.We take the test of our XP2012B,XP2262 and R11102 PMTs for example after completion of the test-system.Result of each PMT is good and the system can work stably to measure the parameters of PMT accurately and quickly.更多还原