Improved double planar probe data analysis technique.

Area of Science:

• Plasma Physics
• Atomic and Molecular Physics
• Electrical Engineering

Background:

• Accurate measurement of plasma density is crucial for understanding plasma behavior.
• Langmuir probes are common diagnostics, but discrepancies can arise between different probe types.
• Weakly collisional argon (Ar) plasma is relevant in various industrial and research applications.

Purpose of the Study:

• To investigate and resolve a factor of two discrepancy in plasma density measurements.
• To compare electron density measurements from a single planar Langmuir probe and ion density from a double planar probe.
• To validate the application of Sheridan's empirical formula for sheath expansion in double probe analysis.

Main Methods:

• Utilized a dc multidipole device to generate weakly collisional Ar plasma.
• Employed a single planar Langmuir probe for electron density measurements.
• Used a double planar probe for ion density measurements.
• Applied Sheridan's empirical formula to correct double probe data.

Main Results:

• A significant discrepancy (factor of two) was initially observed between single and double probe density measurements.
• Application of Sheridan's empirical formula for sheath expansion successfully resolved this discrepancy.
• The corrected double probe data agreed with the single probe electron density measurements.

Conclusions:

• Sheridan's empirical formula is effective in correcting sheath expansion effects for double Langmuir probes.
• Accurate plasma density determination requires careful consideration of probe physics and sheath effects.
• This work provides a method for reconciling density measurements from different Langmuir probe configurations.