Electrostatic Simulation and Analysis of Transmission Line Corner Section for the CRAFT NNBI Test Platform

The gas-insulated transmission line (GITL), which is an important link between ion source and the power supply system,carries all the ion source and the extraction power supplies (ISEPS) conductors at −400 kV with respect to ground, from high voltage deck (HVD) to the ion source and the intermediate potentials of acceleration grids (AGs). In this article, three insulation schemes of the corner section of the GITL are put forward. Through the finite element analysis, only one scheme satisfies the design requirements. In this analysis, the relationships betweenthe design parameters (the radius and angle of the corner section) and the design guiding principles (maximum electric field strength, equivalent distributed capacitance, and so on) are obtained. According to design requirements, the preliminary design parameters of the corner section are determined: the radius of the corner section can change from 50 to 150 mm and the angle of the corner section is chosen as 90 degree. In this case, the maximum electric field strength of the GITL decreases from 3.18 to 3.06 kV/mm, the maximum electric field strength of the inner surface of the grounding shell decreases from 1.08 to 0.73 kV/mm, the electric field non-uniformity coefficient decreases from 2.21 to 2.15, and the equivalent distributed capacitance increases from 82.12 to 94.70 pF. The simulation results provide a theoretica basis for the engineering design of the corner section of the GITL.