VISAR signal analysis with an emphasis on ellipse fitting

Area of Science:

• Physics
• Optical Metrology
• Materials Science

Background:

• Velocity Interferometer System for Any Reflector (VISAR) is crucial for shock wave experiments.
• VISAR signals can suffer from amplitude and phase angle imperfections.
• Existing analysis methods may lack accuracy, especially with fractional fringe signals.

Purpose of the Study:

• To develop and validate an enhanced ellipse fitting method for VISAR signal analysis.
• To improve the accuracy of free surface velocity history reconstruction from VISAR data.
• To address measurement errors caused by signal imperfections.

Main Methods:

• Investigated errors in VISAR signal amplitude and phase angle.
• Developed a novel ellipse fitting technique combining Gauss-Newton and Bookstein methods.
• Performed theoretical justification and numerical simulations of the ellipse fitting technique.
• Validated the method using VISAR signals from shock wave experiments on Al-2024T4.

Main Results:

• The proposed ellipse fitting method demonstrates superior accuracy compared to existing techniques.
• The method effectively mitigates errors introduced by common VISAR signal imperfections.
• Successful validation using experimental shock wave data on Al-2024T4.
• Achieved good agreement with independently sourced data.

Conclusions:

• The novel ellipse fitting technique offers a significant improvement for VISAR signal analysis.
• This method is particularly beneficial for handling fractional fringe signals.
• The validated technique provides reliable and accurate free surface velocity histories in shock wave research.