Stimulation Study Of An X-band Relativistic Magnetron With Diffraction Output

With the continuous development of high-power microwave technology(HPM), a significant development direction of high power microwave generation device is to achieve smaller volume and more compact structure. The relativistic magnetron with diffraction output(MDO) is an important device to meet this trend for it has small volume and weight, compact structure high stability, long working life, radiating different TE modes. At present, the investigations of the MDO mainly focus on microwave generation mechanism, operation and radiation characteristics at the relative low frequency band, such as S-band and L-band. The structural and operating characteristics of MDO at higher frequencies are scarcely studied. The microwave at high frequency has advantages of narrow beam and fine direction, which is widely applied. Therefore, an investigation of an X-band MDO is carried out in this dissertation. The main contents are listed as follows.Firstly, a theoretic investigation on the X-band MDO is carried out. The dispersion relations of the magnetron structure and diffraction output structure are analyzed and the influence of the dispersion relation on the structural parameters is discussed. The results indicate that the resonant frequency of the ? mode reduces with the increase of the radius of the cathode, meanwhile the radius and the opening angle of the cavities, and increases as the radius of the anode and the diffraction output aperture increase. The results indicate that the cutoff wave number of the ? mode reduces with the increase of the radius of the anode and the opening angle of the cavities, and increases as the surface radius of the diffraction output structure and the number of the cavities increase. On this basis, the structure of the X-band MDO is designed.Secondly, the X-band MDO is modeled by a 3-D particle-in-cell(PIC) code. The structure parameters and the external magnetic field are optimized via the PIC simulation. The tilt angles of the anode and the cavity are optimized to 8° and 90°, respectively. The radius of the diffraction output aperture and the operation magnetic field are optimized to 32.8mm and 0.41 T, respectively. A microwave with a power of 1.08 GW, a frequency of 9.58 GHz is generated by PIC simulation. The diode voltage and the beam current are 370 k V and 11.7k A, respectively. The efficiency reaches to 25.1%. The dominate mode of the output is TE01 mode and its purity arrive at 99.54%. Based on the optimized result, the influences of the high frequency structures and external magnetic field on the output characteristic of the X-band MDO are discussed.Finally, the influences of the opening angle number and their locations of the diffraction structure on the characteristics of the radiation microwave of the MDO are investigated via PIC simulation method. The mode components are obtained by the mode analysis method. The results show that a number of n of the opening angles should be adopted to achieve a microwave output with high power and high mode purity in a MDO with a number of 2n of the cavities.