| 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. |
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