Research Of Key Technologies On Electron Cyclotron Resonance Heating Transmission System Of The HL-2M Tokamak

Electron cyclotron resonant heating (ECRH) system is various aspects of controlled magnetic confinement fusion research, e.g., plasma heating, current drive, assistant start-up, current profile control, magnetohydrodynamic (MHD) instabilities control and transport study etc. Generally speaking, ECRH has advantages of quite localized heating profile, high efficiency in wave-plasma coupling and long distance between the launcher and plasma compared to other radiofrequency heating methods. Based on development of ECRH systems for the HL-2M divertor tokamak of China, the key technologies of ECRH transmission system (TS) have been researched. The research mainly focus on the guided wave theory of the TS, the wave transmission power losses analysis and the vector diffraction grating study for design of millimeter-wave (MMW) polarizers. On the basis of theoretical and experimental studies, various high power MMW components, including the overmoded corrugated circular waveguide (OCCW), the integrated mitre bend, the sliding&pumping waveguide, the DC break and the controllable polarizer, were designed for the vacuum TS (<10-2Pa) of the ECRH systems on HL-2M device. The power capacity of these components is1MW/3s.This dissertation is mainly composed of three parts.The first part is Chapter II and Chapter III, where detailed discussion on the guided wave theory of the ECRH TS and analysis on the wave transmission power losses are given to prepare for the OCCW related components development. Firstly, starting with the characteristic equation of the OCCW, the wall function, the eigenvalues and the wall attenuation of the OCCW were solved; the two equivalent mode sets, i.e., the hybrid mode set and the linearly polarized mode set, for the OCCW was derived. In addition, the degenerate relationship between these two sets was given; and the multimode propagation characteristics were studied. Then the mode matching method was introduced to analyze three kinds of mode conversion losses (MCLs) in the ECRH TS. The first one is the mode excitation loss. The ideal&non-ideal cases and also the excitation of spurious modes in the non-ideal situation were discussed; the second one is the waveguide misalignment loss. The losses caused by the tilt and offset at the waveguide junction were derived; the last one is the waveguide gap loss. In this case, the influence of the ratio and phase of the spurious modes on the gap loss was analyzed. Finally, experiments with a68GHz ECRH system were carried out and it verified that the TS based on OCCW can transmit the MMW with high efficiency and stability.The second part is Chapter IV, in which the vector diffraction grating theory with the coordinate transformation method (C method) for design of polarizers has been derived. This section firstly introduced the C method. Afterward, the eigenvalue equation of the grating and the linear equations for the TE and TM polarization mode were obtained; and a code based on the C method was developed and the calculation results were compared with that of the integral method. Then the polarization characteristics of the diffraction grating were been studied; the selection principle of grooves’period of the diffraction grating was given; the influence of the grooves’period and depth on the polarization characteristics was discussed; and a set of optimized groove parameters which are independent on the frequency was given. Finally, the low power experiment was done in order to verify that the calculation results of the C method are correct.The third part is Chapter IV, where the ECRH vacuum transmission components was designed on basis of the research in the former two parts, the power loss of the components was analyzed, and also the vacuum performance of these components was tested. All the components except the controllable polarizer can be used at two frequencies,140GHz and105GHz. Firstly, the corrugation parameters of the OCCW was chosen and the manufacturing process of the OCCW especially that of the1m OCCW was considered. In this way, waveguides with length of200mm,300mm,500mm and1000mm were developed and the losses of the OCCW at two frequencies (140GHz and105GHz) were calculated. Based on the design of the OCCW, its related components including the integrated mitre bend, the sliding&pumping waveguide and the DC break were designed. Moreover, the power loss model of the gap was used for the calculation of mode conversion losses in the mitre bend and the DC break. The140GHz and105GHz remote controllable polarizers were designed respectively with the C method, and the rotation performance of polarizers under vacuum was tested. Finally, the layout of the ECRH transmission systems was considered and the losses are anlysed.