Apparatus for generating quasi-free-space microwave-driven plasmas

Area of Science:

• Plasma Physics
• Microwave Engineering
• Vacuum Technology

Background:

• Microwave-driven plasmas are crucial for various scientific and industrial applications.
• Generating stable quasi-free-space plasmas requires precise control of microwave power and gas conditions.
• Existing methods may have limitations in scalability or spatial control.

Purpose of the Study:

• To design, construct, and test a novel apparatus for generating quasi-free-space microwave-driven plasmas.
• To investigate the operational parameters for sustained plasma discharges.
• To demonstrate the efficacy of a Koch-type metal plate lens for plasma generation.

Main Methods:

• Apparatus design incorporating a multi-kW, ~5 GHz microwave beam.
• Utilized a Koch-type metal plate lens to focus the microwave beam within a vacuum chamber.
• Conducted experiments with argon gas at controlled pressures (150-200 mTorr) and flow rates (~200 SCCM).
• Varied microwave beam power levels (5-10 kW) to achieve plasma generation.

Main Results:

• Successfully generated sustained plasma discharges in argon.
• Achieved stable plasma generation within the tested pressure range of 150-200 mTorr.
• Demonstrated plasma generation across a microwave power range of 5-10 kW.
• Confirmed the effectiveness of the focused microwave beam for plasma sustainment.

Conclusions:

• The designed apparatus is effective for generating quasi-free-space microwave-driven plasmas.
• The Koch-type metal plate lens enables efficient focusing of microwave power for plasma sustainment.
• The system provides a controllable method for producing argon plasmas under specific experimental conditions.