Numerical simulation and optimization of cooling flow field of cylindrical cathode with annular magnetic field

Abstract

In order to solve the problems of unstable discharge, low deposition rate and large difference in ionization rate between different targets in high power impulse magnetron sputtering, a novel cylindrical cathode with annular magnetic field based on hollow cathode effect is proposed, which can be used to produce ion beam with high ionization rate, high plasma density and no large particles. However, the traditional channel structure could not guarantee its high efficiency and uniform heat dissipation. The sealing ring may be damaged by ablation due to high power density, which restricts the further improvement of power density. Therefore, it is necessary to optimize the design of the channel structure. SolidWorks flow simulation software is used to simulate the cooling channel of plasma source. The influence of water hole structure parameters on cooling effect is analyzed, including distribution angle, hole number, diameter and inlet hole height. And the channel structure parameters are optimized. The results show that the increasing of the circumferential distribution range of the water hole is beneficial to the uniformity of heat dissipation, ensuring a large temperature difference between cooling water and copper sleeve, and strengthening heat exchange. The water inlet hole set in the upper layer of the structure is conducive to alleviating the temperature stratification phenomenon of the cooling water, so that the copper sleeve and sealing ring are in good cooling condition. Appropriately reducing the aperture is beneficial to increasing the cooling water jet velocity, enhancing the jet impact effect, and then increasing the turbulence degree, strengthening the heat transfer and improving the heat transfer efficiency. By systematically studying the influencing factors, the optimized cooling flow field structure of cylindrical cathode with an annular magnetic field is obtained. The distribution angle is 30°, the number of holes is 6, the aperture is 4 mm, and the height of water inlet hole is 36 mm. The optimized channel structure can improve the utilization rate of cooling water, obtaining better cooling effect at the same flow rate, and improving the discharge stability of the plasma source, which provides a basis for designing the cooling structure of the cylindrical cathode with annular magnetic field.