Electron density measurement in low-density plasma of electrical wire explosion using a Shack-Hartmann wavefront...

Area of Science:

• Plasma Physics
• Optical Diagnostics
• Wavefront Sensing

Background:

• Measuring low-density plasma electron density is challenging due to limitations in traditional diagnostic sensitivity and spatial resolution.
• Corona plasma generated by electrical wire explosions presents unique diagnostic difficulties.

Purpose of the Study:

• To present a novel electron density diagnostic method for corona plasma using a Shack-Hartmann wavefront sensor.
• To improve the accuracy and spatial range of low-density plasma diagnostics.

Main Methods:

• Utilized a Shack-Hartmann wavefront sensor integrated with a nanosecond pulsed laser and high-resolution camera.
• Employed neural network methods and micro-lens optical simulations for sub-pixel centroid localization.
• Validated the technique against laser interferometry for corona plasma generated by silver-wire explosions under pre-pulse conditions.

Main Results:

• Achieved sub-pixel accuracy (0.25 pixels) with a 21% reduction in shift errors compared to conventional methods.
• Demonstrated theoretical sensitivity up to 2 × 10^15 cm^-2.
• Measured a minimum electron density of 2.2 × 10^16 cm^-2 at 4.4 mm from the wire axis, showing a broader spatial range than laser interferometry.

Conclusions:

• The Shack-Hartmann wavefront sensor method is effective for diagnosing corona plasma electron density, especially in low-density regions.
• This technique offers enhanced spatial range and accuracy compared to existing methods.
• Future work aims to optimize the system for reduced errors and application in large-scale pulsed power facilities.