Dynamics of relativistic laser-plasma interaction on solid targets.

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• High-Energy-Density Physics

Background:

• Understanding critical surface dynamics is crucial for laser-driven fusion and particle acceleration.
• Previous studies lacked time-resolved measurements of relativistic laser-solid interactions.

Purpose of the Study:

• To investigate the time-resolved motion of the critical surface during picosecond-scale relativistic laser interaction with solid targets.
• To elucidate the physical mechanisms responsible for changes in the hole boring process.

Main Methods:

• Utilized a novel time-resolved diagnostic to record critical surface motion.
• Performed single-shot measurements of specular light to detect redshift.
• Conducted on-shot full characterization of the laser pulse.
• Employed two-dimensional particle-in-cell simulations validated by experimental data.

Main Results:

• Observed a time-decreasing redshift in specular light, indicating a slowing hole boring process.
• Experimental data agreed with particle-in-cell simulations without free parameters.
• The slowing of the critical surface was supported by simulations.

Conclusions:

• The hole boring process in overdense plasma decelerates over time.
• Momentum conservation between ions and reflected laser light provides a simple explanation for the observed slowing.
• The study provides new insights into fundamental plasma physics under extreme conditions.