Research On 140 GHz Gyrotron Traveling Wave Amplifier With Helically Corrugated Waveguide

Gyrotron traveling-wave amplifier(gyro-TWT)is an important signal amplifying device and has great research potential in high-resolution radar,communications and electronic warfare due to its characteristics of high output power and wide working frequency.The gyro-TWT has been paid more and more attention by scientists and has become an important research topic.There are certain limitations for gyro-TWT using smooth-wall waveguide as high-frequency structure in improving the output power and working bandwidth,while the gyro-TWT which uses helically corrugated waveguide as high-frequency structure can achieve a great improvement in these aspects and restrain the mode competition in the waveguide.The working ability of the gyro-TWT is greatly improved by these properties of the helically corrugated waveguide.The gyro-TWT with helically corrugated waveguide,in addition,has better working stability and reduces the requirements for the design and processing of the electron gun due to its low sensitivity to electron-beam velocity spread.So gyro-TWT with helically corrugated waveguide becomes a research hotspot.The 140 GHz gyro-TWT with helically corrugated waveguide is studied in the article with main work listed as follows:1.The mechanism of Electronic Cyclotron Resonance Maser(ECRM),the development history and main design ideas of gyro-vacuum devices and gyro-TWT based on the ECRM mechanism is sorted out and studied.The defects of traditional gyro-TWT are analyzed and the gyro-TWT with helically corrugated waveguide is introduced.2.The helically corrugated waveguide is introduced.Also,the mode conversion process of the electromagnetic wave propagating in the helically corrugated waveguide and the working process of gyro-TWT with helically corrugated waveguide are analyzed.The helically corrugated waveguide is analyzed and the dispersion equation,the angular coupling condition and the coupling coefficient equations of different modes satisfying the angular coupling condition are deduced according to the mode coupling theory and impedance perturbation method.3.A Matlab program is used to numerically simulate the dispersion characteristic and analyze the variation law of the dispersion characteristic of the helically corrugated waveguide.The helically corrugated waveguide is simulated and the transmission characteristics and field distribution of the waveguide are analyzed with the help of CST simulation software.4.An electron gun matching the 140 GHz gyro-TWT with helically corrugated waveguide was designed according to the design method of the electron gun and the working requirements of the gyro-TWT.The influence of the structure parameters of the electron gun on the ratio of transverse to longitudinal velocity of the electron-beam is analyzed,and an electron gun with the ratio in the interaction zone about 1.2 is obtained.5.The PIC simulation of a 140 GHz gyro-TWT with helically corrugated waveguide shows that when the frequency and power of the input signal are 140 GHz and 50 W respectively,the output power is 223 kW and the gain reaches 36.49 dB.The output power is between 113 kW and 223 kW when the operating frequency is within the frequency range of 134 GHz to 142 GHz and the spectrum of output signal is pure without parasitic oscillation.In addition,the influence of different parameters on the effect of beam-wave interaction is also analyzed.Finally,its working effect is verified under low working current and low input power.