| This paper deals with the electromagnetic problem of high voltage transmission line of the neutral beam injection system in the ESAT tokamak, such as the partial capacitance calculation of the transmission line. According to the neutral beam injection system and the design requirement of the high voltage transmission line, two design schemes are given which include the non- coaxial and coaxial configuration transmission line. The method of calculating the partial capacitance can be determined after analyzing and comparing these different design schemes. The capacitance of the transmission line of the non- coaxial configuration for the auxiliary power supplies is solved with the help of the finite element analyzing software—ANSYS, and the capacitance of the transmission line for the acceleration grids power supply is calculated in an analytical method. Due to the geometry of the transmission line of the quasi-coaxial configuration with multilayer and coaxial conductor shell, a series of image charges relating to the parallel conductor can be found by multiple image method, and the partial capacitance can be obtained by calculating the coefficient of potential among the conductors. The capacitance between the two coaxial cylindrical shells is required to be calculated by analyzing the transmission line of the coaxial configuration, also it can be obtained in an analytical method. The result in this paper is very important for designing the neutral beam injection system, and it provides reference for the project of the high voltage transmission line and the acceleration grids safeguard of the neutral beam injectors. |
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