The Study Of Time-of-Flight Counter Made Of Plastic Scintillator

This paper begins with a brief introduction of the past and current status of particle physics and particle detector. The performance of the particle detector becomes more and more important for high energy physics as the modern technology of computer and electronics grows; the discovery potential of new particles and physical phenomena is determined by the whole performance of the huge detector. The Beijing Electron Positron Collider (BEPC), composed of the linear accelerator, the transportation line, the storage ring and the Beijing Spectrometer (BES), is a most important machine for high energy experiment in our country, and makes us have a seat in the international community of high energy physics research. Although it had great achievements in the past years, but now as the detector became aged it is hard for it to continuously play a leading role in the tau-charm physics study to meet the requirement of rapid development in high energy physics. Hence, it is the right time to upgrade BEPC machine and BESII detector, to make its performance be greatly improved based on its past successful operation, and then the high-class physics results in the world would be obtained continually. However, the whole performance of the huge machine depends on its each sub-detectors; the upgrade project would be completed successfully only if all its sub-detectors are better designed and precisely installed.This dissertation is mainly focused on the study of Time-of-Flight (TOF) counter system made of plastic scintillator. As a sub-detector of BESIII currently under construction, TOF system is powerful for charged particle identification (PID) of K/Ï€ with a momentum less than 1 GeV/c. At the same time it can also provide the fast trigger and event timing information. This kind of detectors is widely used because of its mature technology. However, in order to make the performance of BESIII TOF counter close to or exceed the international advanced level, some detailed studies and beam tests have to be done.The properties of the scintillator and photomultiplier, the two important part of TOF counter, are very pivotal. Through detailed investigation and referring to other detectors, three kinds of scintillators, BC-408, BC-404 and EJ-200, are selected. The peak position of their emission spectrum is at 425 nm, 407 nm and 426 nm respectively from experimental study, this peak position and shape of the spectrum remains unchanged even after being irradiated by strong irradiation resource; the relative light yield of all the samples decreases when the radiation dose increases; no evidence of recovery of light yield is observed within 100 hours after weak irradiation; the transmittance of BC-408 and EJ-200 is about 70%, and that of BC-404 is just little lower. Hence, all of them can be used for the TOF counter since the estimated dose rate at BEPCII is 10 Gy per year, but BC-408 and EJ-200 are preferred. Considering the size and emission spectrum of scintillator, the limited detector inner space, and the parameter of PMT, the shorter PMT R5924 made by Hamamatsu Company is chosed. The test results show that the diamagnetism and time performance of PMT R5924 meets our goals.The beam test and Monte Carlo simulation of a single TOF counter composed of...