High-speed plasma measurements with a plasma impedance probe

Area of Science:

• Physics
• Plasma Physics
• Electrical Engineering

Background:

• Plasma impedance probes (PIPs) are essential for measuring electron density in plasmas.
• Existing methods have limitations in accuracy and time resolution.

Purpose of the Study:

• To introduce advancements in PIPs for improved electron density and damping measurements.
• To achieve time-resolved PIP measurements at frequencies of 1 MHz and above.

Main Methods:

• Developed a streamlined analytical model incorporating sheath thickness for PIP-monopole measurements.
• Implemented higher-frequency hardware, updated algorithms, and rigorous RF calibration for high-speed measurements.
• Validated the model using quasi-static numerical simulations.

Main Results:

• The new model provides more accurate electron density and damping measurements.
• Achieved ≥1 MHz time-resolved measurements, resolving plasma oscillations up to 150 kHz at 4 MHz.
• Demonstrated application to datasets with densities ranging from 2 × 10^14 to 3 × 10^15 m^-3.

Conclusions:

• The enhanced PIP model and high-speed techniques significantly improve plasma diagnostic capabilities.
• These advancements offer greater accuracy and temporal resolution for studying dynamic plasma phenomena.
• Provides criteria for optimizing PIP design to minimize measurement uncertainty.