New Design Method For Testing System Parameter Of Low Energy Electron Counter

The fatigue damage of the metal material often happens under the action of the dynamic load. The accumulation of fatigue damage of the metal material leads to surface fatigue cracks. There are a lot of traditional methods of NDT (Non-Destructive Testing) to the formed crack. But mostly it is very difficult for these methods to realize the on-line real-time supervision of the crack being formed. At present a large number of researches indicate that the surface of metal material while the crack forms, can emit massive low energy electrons. The aim of the intelligent low energy electron sensor system discussed in this dissertation is to accurately examine the number of low energy electrons launched from metal material surface. Therefore, it has the vital scientific significance and the application value in carrying out this research work of the metal material NDT.The key study contents in the dissertation are as follows:1. The low energy electron launch mechanism and counter, the domestic and foreign research survey and the tendency, and the application of the low energy electron in the field of NDT are briefly introduced.2. According to the physical character of DGAC, gas discharge in DGAC is analyzed. Controllability of discharge in DGAC is proved. Based on its controllability, the paper built a discrete mathematics model of discharge. Using this model, we optimized the DGAC with the help of computer.3. The quenching of discharge is an important problem in DGAC. In this paper, two times gas discharge theory is suggested and the width and height of the quenching pulse needed by DGAC is calculated based on this theory.4. The movement of the irons in the counter and secondary electron emission are discussed respectively, and the irons' action and effect on the counter are put forward. At last the simulation figures on the material used on the surface of the counter are plotted. After frequency analysis of discharge current, preamplifier is designed and its input impedance is calculated.Experiment results show that the optimization of main parameter in DGAC is reasonable and the analysis of quenching process is right. The pre-amplification circuit, the quenching circuit and the suppression circuit conform to the design requirement. The work discussed in the dissertation has laid the good foundation for the intelligence of low energy electron sensor system.The research has received the subsidy of the National Natural Science Fund of China (50275125) and the Aviation Science Fund of China (04153068).