A washer gun plasma system for microwave-plasma interaction experiments.

Area of Science:

• Plasma physics
• Microwave engineering
• Fusion energy research

Background:

• High power microwave (HPM)-plasma interaction requires specific plasma conditions.
• Existing systems may not provide the necessary density, uniformity, and gradient control.

Purpose of the Study:

• To develop and characterize a washer-gun based plasma system for HPM-plasma interaction experiments.
• To achieve critical plasma parameters including density, uniformity, and axial gradient.

Main Methods:

• Utilized a washer-gun plasma source driven by a ten-stage pulse forming network.
• Generated pulsed discharges (τ_pulse ≈ 100 μs) with electron densities (n_e) up to 10¹⁸ m^-3 and electron temperatures (T_e) of 10 eV.
• Identified temporal and spatial regimes for plasma characterization.

Main Results:

• Achieved n_e ≈ 10¹⁸ m^-3, meeting critical density requirements.
• Obtained radial uniformity over ≈10 cm and axial uniformity over ≈20 cm.
• Demonstrated control over axial density gradients (L_n ≈ 10 cm) and tailored plasma profiles for 3-5 GHz HPM frequencies.

Conclusions:

• The developed washer-gun plasma system successfully meets the stringent requirements for HPM-plasma interaction studies.
• The system offers tunable plasma parameters, enabling flexible experimental designs.
• This work provides a characterized plasma source for advanced microwave plasma experiments.