Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma source

Area of Science:

• Plasma Physics
• Atomic and Molecular Physics
• Ion Source Technology

Background:

• Negative ion sources are crucial for applications like neutral beam injection in fusion reactors and particle accelerators.
• Multicusp plasma sources are widely used due to their ability to confine plasma effectively.
• Microwave-driven sources offer advantages such as efficient plasma generation and reduced electrode erosion.

Purpose of the Study:

• To evaluate the performance of a microwave-driven upper hybrid resonance multicusp plasma source.
• To optimize discharge conditions for maximizing negative hydrogen ion (H-) current.
• To compare experimental results with theoretical estimations based on particle balance equations.

Main Methods:

• Direct microwave launching into the plasma chamber, predominantly in the TE(11) mode.
• Operation of the source under various discharge conditions.
• Solving particle balance equations to estimate negative ion density.

Main Results:

• The optimized negative H- ion current reached approximately 33 μA (0.26 mA/cm²).
• Experimental measurements of negative ion density were obtained.
• Comparison between experimental and theoretical estimations of negative ion density was performed.

Conclusions:

• The microwave-driven upper hybrid resonance multicusp plasma source shows promising performance as a volume negative ion source.
• Optimization of discharge parameters is key to achieving high negative ion currents.
• Further development could enhance the source's efficiency and applicability.