Special Cavity Terahertz Higher Harmonic Gyrotron Research

Terahertz wave refers to the electromagnetic radiation with the frequency range of0.1THz to10THz. In recent years, with the development of generating and detecting THz radiation, terahertz technology has become hotspot of international academia. Therefore, with the rapid development of THz gyrotron which has the maximum output power in terahertz frequency is paid close attention.The magnetic field can significantly be decreased by means of high harmonic operation. However, the use of high order harmonic mode would bring fiercely mode competition. It has become the technical bottleneck of high order harmonic mode working on circular waveguide. Therefore, various gyrotrons with some special cross-section cavities have been proposed in order to develop high harmonic terahertz gyrotrons. However, the theoretical methods are becoming more and more difficult to draw the beam-wave interaction efficiency, coupling coefficient, starting current and other important parameters, which restrict gyrotrons research and design. In order to solve problems above, this paper proposed a novel calculation method of a terahertz gyrotron with special cross-section cavity. The main research and achievements of this thesis are as follows:1. The paper based on the gyrotron linear theory and nonlinear theory proposes combining the nonlinear self-consistent theory and three-dimensional electromagnetic simulation software CST. Through importing electric fields which are the results of CST simulation, the beam-wave interaction efficiency, coupling coefficient and starting current can be obtained. Finally, Compile program by C++2. Make the simulated results of this program contrast to the simulated results of the fundamental, second harmonic and third harmonic gyrotron in theoretical method. It is known that the two results coincide with each other well, which certifies the feasibility and reliability of this method.3. Based on the program above, the beam-wave interaction of the gyrotron with irregular cross section is studied. Through importing high frequency fields which are the results of CST, the beam-wave interaction efficiency, coupling coefficient and starting current can be obtained. In addition, a0.4THz third harmonic TE33mode gyrotron with a corrugated interaction cavity is presented according to the advanced nonlinear self-consistent theory of gyrotrons. The gyrotron with a40.5keV/1A electron beam and magnetic field of5.09T, pitch factor1.5can produce radiation with output power of3.3Kw.