Preliminary Research on Electromagnetic Radiation During Operation of Intense Electron-Beam Accelerator
|School||National University of Defense Science and Technology|
|Keywords||intense electron-beam accelerator electromagnetic radiation gas gap switch time-frequency analysis effect|
Intense electron-beam accelerator has been widely used in fields of nuclear explosion simulation, free-electron laser, source of HPM, medicine and environmental conservation. In our daily experimental studies, it is found that there is strong electromagnetic radiation during operation of intense electron-beam accelerator. This kind of electromagnetic radiation may interfere with the electronic equipment, making the compute nearby come into black screen, and people who have long-term exposure in the radiation environment would suffer from it. In this paper, the source, occasion, characters of frequency, intensity and distribution of radiation are researched by the methods of theory analysis, software simulation and experiment research. The radiation interference in cable is measured.According to the theory analysis, at the moments that three electrodes gas spark switch and main switch close, the high-frequency current and the electron moving with acceleration during the gap of gas switch will result in high intensity radiation. The generation mechanism of high-frequency current is studied, and the circuit of IEBA is calculated using the PSPICE software. The close process of gas switch is analyzed, and the hypothesis of‘electron-group’is developed. Using the simulation result and the hypothesis, the radiation that generated at the moment the three electrodes gas spark switch closes is discussed.The simulation of IEBA, with the whole structure and combination of field and circuit, is researched using the CST software. The distribution and transmission of electromagnetic are showed. At the moments that three electrodes gas spark switch and main switch close, there are intensity radiation at the far field.The radiation in the operation process of intense electron-beam accelerator is measured in the condition of lab using the antenna. The result shows that except for the two sections that occurred at the times three electrodes gas spark switch and main switch close, there is also another section which appears when the trigger pulse arrives. At the point that is 3 m far from three electrodes gas spark switch, the maximal electric field is 1100 V/m. Frequency-time analysis of the first and the second sections have been taken. The main frequency is 20.8 MHz and the maximal frequency is 100 MHz, which is nearly consistent with the result of theory analysis. During the initial time after the trigger pulse comes, lasting for nearly 200 ns, the frequency spectrum is very wide. The relationship between the first two sections radiation and the air pressure of triggered switch is also researched, resulting that at the condition that the charged voltage is 20 kV, radiation intensity together with high frequency portion decrease with the increase of air pressure; the distribution of radiation in the lab is also measured.At last, the radiation interference in cable is measured. High intensity electromagnetic radiation induces current in cable, which generates interference to the accurate measure of the signal. According to national criterion, this electromagnetic radiation may, to some extent, do harm to the health of human beings. So it is improper to expose in this circumstances.