Research On W-Band High Harmonic Peniotron With Permanent Magnent

The gyrotron is one of the most promising high power and high efficiency millimeter wave device. High power gyrotron has been successfully applied in nuclear fusion plasma, and it also has wide application prospects in millimeter wave ceramic sintering, material processing, millimeter wave communications, millimeter wave weapon(Active Denial System) and high resolution radar, etc. One critical drawback of the millimeter wave Gyrotron is the indispensable part of the superconducting magnets. However, the high price, complexity, and long start up time significantly limit the application of gyrotrons. The peniotron is another kind of cyclotron device which has not been adequately studied and practically applied. Numerous studies have shown that the peniotron has high efficiency and can operate at high harmonics. Therefore, peniotrons have attracted attention of many researchers for the potential advantage that the magnetic field can be provided by the permanent magnet instead of the superconducting magnet. Currently, Japanese scholars have obtained W band microwave radiation with their peniotron. U.S. scholars have also developed corresponding researches on the practical Ka band peniotron and they have proposed detailed plans and experiment results, but the report of their practical W band peniotron prototype has not been shown. In recent years, the high power radiation laboratory of the University of Electronic Science and Technology has conducted the studies of peniotrons, particularly, the design and exploration of Ka band 3rd harmonic peniotron and large cyclotron electron gun. Based on the engineering requirements and possibility analysis, our laboratory has developed the W band 10 kW peniotron with permanent magnet. The project is supported by the National Natural Science Foundation of China.This dissertation aims to develop a W band 10 kW peniotron with permanent magnet. A sysemmatical and comprehensive research on the selection of the overall scheme, theoreticla analysis and design of beam wave interaction system, design of permanent magnet system, design of the electronic optical system, design of hot and cold test system, and the test methods, has been conducted. An RF cavity has been practically fabricated and cold tested, and the measured results agree well with theoretical calculation. Considering the performance of the permanent magnetic material and device efficiency, a 6th harmonic magnetron type slotted peniotron has been proposed. In particular, the high harmonic peniotron has been studied. The mode competition in the 7 slotted resonator has been studied and the possibility of a steady 6th harmonic 2Ï€ single mode operation has been demonstrated. PIC simulation of W band 6th harmonic peniotron has been completed and parameter design of a peniotron with 30 kW output power and efficiency up to 40% has been given. A calculation code for self consistent nonlinear large signal peniotrons has been developed, and the code has been used to study the peniotron performance, when effects of velocity spread, the offset of the guiding center and etc exist. Simulated results show that the 10 kW microwave output power and conversion efficiency of 17% can always be obtained, if the peniotron guiding center offset is no more than 8% and the longitudinal velocity spread is no more than 8%. These results help determine the minimum requirements of the electron beam quality of W band practical peniotron. Based on the possibility of permanent magnet with radial polarization technology, a compact permanent magnet is designed. Although there are some shortcomings for the field distribution of the permanent magnet, the special gradual reversal magnetic field and the uniform area magnetic field can basically satisfy the requirements of large cyclotron electron beam and beam wave interaction for penitrons. With above obtained magnetic field of permanent magnet, a new design concept has been used to design a large cyclotron electron gun of peniotron with a special gradual reversal of magnetic field. Simulated results show that 5.4% guiding center offset, 6.9% longitudinal velocity spread, 1.3 transverse velocity spread and 2 speed ratio can be achieved with the special large cyclotron electron beam. The large cyclotron electron gun can completely meet the basic requirements of the above mentioned peniotron. Meanwhile, this dissertation has studied the circulation rules of the compact peniotron under the special gradual reversal of magnetic field with permanent magnet, and proposed the practical methods of monitoring the operation status of the electron gun and optiminzing the electron beam parameters. The measurement technology and system research of the W band peniotron with permanent magnet is for the systematical design of the peniotron. A rectangular waveguide TE10 circluar waveguide TE01 mode converter, and a circular waveguide TE01 rectangle waveguide TE10 diagnosis coupler have been designed to operate the peniotron cold test. The Q value and the operation mode of the peniotron from the cold test agree well with the expectations. Finally, the framework of the W band high harmonic peniotron with permanent magnet had been constructed, and the hot test platform of the peniotron has been completed. The experiments of peniotron are currently in preparation.