Experimental study of the rotation characteristics of magnetically driven vacuum-arc cathode spots

Achieving uniform, stable, and reliable erosion of electrode materials is crucial for enhancing the performance and lifespan of vacuum-arc devices. This study investigates the rotation and erosion characteristics of cathode spots on Cu and Ti cathodes with various applied magnetic fields. The results indicate that with the discharge current changes, cathode spots evolve from a single spot to multiple spots and then back to a single spot. Without an applied magnetic field, Ti cathode spots exhibit a large-scale random walk, while Cu cathode spots show a concentrated distribution. With an applied magnetic field, cathode spots of both materials undergo directional rotation. The velocity of the Ti cathode spots is higher than that of Cu, and spot velocity increases with the increase of magnetic flux density. When the radial magnetic field is enhanced to 70 mT, the rotational velocity of the cathode spots actually decreases with the increase of the peak current. The increase of applied magnetic field leads to a significant decrease in the total erosion rate and macroparticle loss, accompanied by an increase in the average ion charge state. The application of an applied magnetic field can effectively regulate the rotation of cathode spots, allowing both Cu and Ti cathode spots to rotate for more than one full circle. Scanning electron microscopy observations indicate that the dimensions of the erosion craters on the cathode surfaces are significantly reduced, leading to a substantial improvement in the uniformity of erosion.