Simulation And Analysis Of The Inverse Magnetron Injection Gun For THz Gyrotron

With the development of terahertz science and technology,the source devices of terahertz have also received more attention.Among them,the gyrotron has received extensive attention from scholars all over the world because of its advantages such as higher operating frequency and higher output power.However,with the gradual increase in the demand for high power of the gyrotron,the traditional electron gun has problems such as electronic interception and cathode emission area limitation.Inverse magnetron injection gun process some obviously advantages compared to traditional magnetron injection gun in high-power,high-frequency gyrotron.Aiming at the working parameter requirements of the 0.24 THz megawatt-level gyrotron,an inverse magnetron injection electron gun is designed based on the hot cathode and the field emission cathode respectively.The main contents of this paper are as follows:1.The movement state of the electron beam in the electromagnetic field of the electron gun is deduced and analyzed in the cylindrical coordinate system;based on the structure model and required performance of the electron gun,the advantages and disadvantages of the inverse magnetron injection gun and the conventional magnetron injection gun are compared and analyzed.The principle of field emission cathodes is introduced in detail,and the related equations are derived.2.According to the relevant theory of the electron gun,calculate the target parameters and preliminary structure parameters of the electron gun,then optimize each parameter and explore and analyze its influence on the electron beam performance,and use the method of coating the finite conductivity loss layer to suppress the oscillation,The main performance parameters of the optimized electron beam are: the pitch factor is1.32,the spread in pitch factor is 2.43%,the guiding center radius is 9.55 mm,the spread in transverse velocity is 0.86%,and the beam current is 42 A.3.By solving the field emission equations,the parameters of the field emission cold cathode are determined.The effects of various parameters on the performance of the electron beam are derived under the two conditions of cold cathode emission saturation and cold cathode emission unsaturated.And a field emission cathode reverse magnetron injection electron gun is designed,which makes the pitch factor is 1.24,the spread in pitch factor is 1.64%,and spread in the guide center radius is 2.81%,the spread in transverse velocity is 0.77%,and the beam current is 19.7A,meeting the expected design requirements.