Simulation And Design Of High-Order Harmonic Terahertz Gyrotron Traveling Wave Amplifier

Terahertz wave is an electromagnetic wave in the range of 0.1THz?10THz,it has the advantages of high resolution,ultra-wide bandwidth and so on.Gyrotron traveling wave tube is a high power vacuum device which based on electron cyclotron maser effect.The quasi-optical gyrotron traveling wave amplifier is a kind of gyrotron traveling wave amplifier which interaction structure is quasi-optical waveguide.When it works on the fundamental harmonic wave,the gyrotron traveling wave tube has a higher demand on the working magnetic field,high order harmonics can be used to solve this problem.The second or third harmonic mode is suitable for the gyrotron traveling wave tube.In this thesis,the quasi-optical waveguide is used as the interaction structure,we research the traveling wave amplifier which works on two harmonic mode.The main contents are:1.Theoretical analysis and research on the alignment cavity structure.The Gauss beam in the quasi-optical cavity is studied deeply,and the expression of the electromagnetic field in the cavity is obtained by the derivation of the equation.The diffraction loss of different modes in the quasi-optical cavity is analyzed,and the mode sparsity in the circular waveguide and the quasi optical waveguide is analyzed.When we choose the working mode some factors should be considered.2.Based on the basic theory of gyrotron dynamics,the dispersion curve equation of electron cyclotron maser is obtained.The cold cavity simulation is performed to optimize the structural parameters.The input structure is designed using standard WR8 waveguide.Based on the geometrical optics method,the HE06 mode of the quasi optical waveguide is converted into a rectangular waveguide mode.3.First of all,the gyro traveling wave amplifier operating in the fundamental 0.14 THz is studied.It is analyzed that the quasi-optical truncation structure can stabilize the amplifier.When the input power is 1W,the output power of 1.25 kW is obtained,and the gain is 31 dB.4.Then on the basis of the fundamental harmonic research work in the two harmonic 0.14 THz gyrotron traveling wave amplifier,design the structure,due to the 3D model we simulationed it,in this way,we optimized the structure parameters and electrical parameters.When the input power is 3W,the output power is 382 W,the gain is 21 dB,and the bandwidth is 3.2GHz.