Simulation And Analysis Of Electron Optical System For 0.65 THz Gyrotron

In recent years,Terahertz Science and technology has attracted widespread attention in the world because of its unique charm.The research on terahertz wave sources is a hot topic.The gyrotron based on the principle of free electron stimulated radiation(FESR)overcomes the commonality of high frequency structure size and working wavelength,and becomes the most likely device to output high power terahertz wave.The double-anode magnetron injection gun studied in this paper is the source of transmitting electrons for 0.65 THz second harmonic gyrotron.Because the cut-off radius of high frequency cavity of gyrotron is only 1.3 mm,the average guiding center radius of the required electron beam is 1 mm,the gyrotron has a high requirement for electron beam,and the velocity dispersion and guiding center radius dispersion can not be too large.Otherwise,the interaction efficiency will be seriously affected.When the radius of conduction center is too discrete,the electron beam will even hit the second anode and can not enter the high frequency cavity.The main contents of this paper are as follows:1.Based on the conservation of angular momentum and adiabatic compression theory,a set of equations for calculating the initial structural parameters of electron gun is analyzed,deduced and summarized.In order to understand the motion law of electrons in the electron gun area and the fundamental reason for the dispersion of electron beam velocity,the electromagnetic field distribution in the electron gun area was analyzed.According to the initial structure parameters of the electron gun,PIC simulation is carried out,and the rules of the influence of various parameters on the performance of the electron beam are analyzed and summarized.Finally,a good performance electron gun is obtained.The velocity ratio of the electron beam emitted by the gun is 1.28,the velocity ratio is 3.8%,the transverse velocity is 1.46%,the longitudinal velocity is 2.25%,and the average guiding center radius is 1 mm,which meets the second harmonic return of 0.65 THz.The requirement of the spindle for the electron beam.2.The study of electron beam falling point is very important for the design of collector position and power capacity.In this paper,by simplifying the structure of high frequency interaction,the electron beam emitted from cathode is simulated to fall to collector through beam-wave interaction process.3.The simulation of electron gun is to put into test and provide electronic source for interaction.However,due to the limitation of processing technology level,there will be some deviation between the simulation and the electronic gun.Therefore,this paper also considers the influence of structural deviation caused by processing accuracy on the performance of electron beam,and simulates how to find the best working point in the gyrotron thermal test experiment.Finally,the design parameters of the electron gun are given.According to the design parameters of the electron gun,a double-anode magnetron injection gun was successfully manufactured and used in the thermal measurement experiment of 0.65 THz second harmonic gyrotron.Through the experimental test,an optimum operating point of the gyrotron was found.The output power was 2.03 kW and the efficiency was 6.7%.The experimental results proved that the designed electron gun has certain reference value.