Effect of hard anodized aluminum coating on vacuum breakdown characteristics under a tens-of-nanoseconds pulsed voltage

Aluminum hard anodizing has been demonstrated to improve the withstand voltage of vacuum gaps and is widely used in grading rings and flares of insulator stacks in pulsed power facilities. However, these coating films are prone to defects that can lead to failure. Understanding of the influence of coating parameters on pulsed vacuum breakdown characteristics has been limited. The effects of the thickness, porosity, and surface roughness of hard anodized aluminum coating on a vacuum breakdown field are investigated in this study. Experiments are performed under a pulsed voltage with a full width at half maximum of 70 ns. The experimental results reveal that the breakdown field increases as the surface roughness of the coating decreases. As the coating thickness increases from 20 to 70 μm, the breakdown field increases from 1040 ± 362 to 1439 ± 38 kV/cm. The results indicated that thicker films, shallower micron-scale pores, smoother surfaces, and reduced porosity are the key factors for enhancing the breakdown field in vacuum gaps. The findings of this study can enable practical engineering applications and improve the performance of pulsed power facilities.