Numerical Simulations Of Structural Misalignment In Coaxial Waveguide And Coaxial Open Resonator

As the device operates in long pulse/CW with megawatt level, the ohmic heating of the gyrotron cavity, such as oscillation and amplifier, walls will get serious. It maybe make the gyrotron cavity can't work as usual. To solve this problem, large-volume cavities must be employed. However, large volume of a cavity may result in multimode operation. In order to solve the problem of ohmic heating and competition modes, one of the most effective means is to employ open coaxial wave-guide or open coaxial resonator, which are made by inserting an inner rod into a cylindrical wave-guide and cavities. Open coaxial resonator makes the spectrum of eigenvalue become not dense.In practical terms, the coaxial structure may inevitably have a deviation between the inner rod and outer wall due to technological factors. So, it is necessary for us to study the effect of structural misalignment in coaxial waveguide and coaxial open resonator. In this paper, the effect is studied by analyzing in theory, numerical simulation and software simulation. Mainly content including:Firstly, the improvement and research of coaxial structure are introduced. The significance, content and innovation points are explained in Chapter 1.In Chapter 2, we introduce the electromagnetic theory of coaxial waveguide,open resonator and open coaxial cavities. Subsequently, three-dimensional electromagnetic emulations software HFSS and CST is introduced in Chapter 3.Latter, the effect of misalignment on coaxial waveguide is researched. The field profile and eigenvalue of the parallel misalignment coaxial waveguide are studied by software HFSS. And the field profile and S parameter of the oblique misalignment a coaxial waveguide are studied by software CST.Finally, two kinds of eccentricity between the outer-wall and inner-rod axes with the open coaxial resonator are studied in Chapter 5. The influence on the field profile, the resonant frequency and Q factor of structural misalignment coaxial resonator are studied by CST.Numerical simulations of structural misalignment in coaxial waveguide and coaxial open resonator are done. Main innovation points in the dissertation are as follows:1. The effects of the oblique misalignment between the inner-rod axis and the outer-wall axis in a coaxial waveguide are studied by means of the software CST microwave studio. Results show that the field profile and S parameter is effected by oblique misalignment.2. In this paper the effects of the misalignment between the inner-rod axis and the outer-wall axis in an open coaxial resonator are studied by means of the software CST microwave studio. Results show that either the parallel misalignment or the oblique misalignment between the inner-rod axis and the outer-wall axis causes substantial decrease of the resonant frequency, the Q-factor, and the field amplitude of the open coaxial resonator, and generally, an oblique misalignment has more adverse influence than a parallel misalignment.