Method for measuring Doppler shifts in arc-heated flows.

Area of Science:

• Plasma Physics
• Spectroscopy
• Fluid Dynamics

Background:

• Accurate measurement of plasma flow properties is crucial for understanding and controlling plasma behavior.
• Traditional methods for determining Doppler and Stark shifts often require multiple measurements or complex setups.
• Plasma jets are widely used in various industrial and research applications, necessitating precise diagnostic tools.

Purpose of the Study:

• To demonstrate a novel, single-measurement method for simultaneously determining Doppler and Stark shifts in spectral lines from plasma jets.
• To develop a technique for accurately measuring radial velocity profiles in supersonic, arc-heated flows.

Main Methods:

• Utilized a Fabry-Perot interferometer combined with a spherical mirror positioned at an angle to the plasma flow.
• Recorded both red- and blue-shifted spectral line profiles in a single scan, with a chopping mechanism for unresolved profiles.
• Employed Abel inversion on integrated line shift data to derive radial velocity profiles.

Main Results:

• Successfully demonstrated the simultaneous determination of Doppler and Stark shifts in a single spectral measurement.
• The wavelength difference between shifted profiles directly yields the integrated Doppler shift, independent of Stark shift.
• Stark shift is determined by the difference between the absolute line center and the midpoint of the shifted profiles.
• Achieved radial velocity profile accuracy of +/-3% in a supersonic, arc-heated argon flow.

Conclusions:

• The novel spectroscopic method provides an efficient and accurate means for plasma flow diagnostics.
• This technique simplifies the measurement of Doppler and Stark shifts, crucial for plasma characterization.
• The demonstrated accuracy supports the application of this method in supersonic, arc-heated plasma flow analysis.