Stepwise Density Increases with an Additional Downstream Solenoid Field in a Low-Aspect-Ratio, Large-Diameter RF Plasma Source

抄録

Additional electromagnets enable adjustment of the external DC magnetic field condition by varying the DC current applied to each electromagnet in a developed, large-diameter (LD), low-aspect-ratio (LAR) radiofrequency (RF) plasma source using a flat spiral antenna. The magnetic field topology downstream changes in three cases: diverging, uniform, and converging fields, while the field strength near the flat spiral RF antenna remains nearly unchanged. Electron density increases stepwise with increasing RF power, and the transition thresholds systematically shift toward lower RF power as the downstream magnetic field becomes more convergent. The lowered threshold power may be related to reduced axial electron loss under the converging-field condition. These results indicate that control of the downstream magnetic-field topology can modify the RF power threshold for accessing higher-density plasma branches in the LD-LAR RF plasma source.