Hot-electron surface retention in intense short-pulse laser-matter interactions

Area of Science:

• Plasma physics
• Laser-plasma interactions
• Computational physics

Background:

• Intense short-pulse lasers deposit energy into hot electrons in plasma.
• Understanding hot electron behavior is crucial for applications like inertial confinement fusion.
• Steep density gradients and magnetic fields influence electron transport.

Purpose of the Study:

• To investigate the retention of hot electron energy near the surface of plasma targets.
• To explore the mechanisms behind hot electron confinement in laser-irradiated targets.
• To assess the implications of hot electron retention for applications such as fast ignition and radiography.

Main Methods:

• Implicit hybrid plasma simulations were employed.
• Analysis focused on targets with steep density gradients illuminated by intense short-pulse lasers.
• Mechanisms considered include lateral electron transport, spontaneous magnetic fields, geometric effects, and electric fields.

Main Results:

• A significant fraction of deposited energy is retained in hot electrons near the target surface.
• Hot electron retention is influenced by lateral transport, spontaneous magnetic fields, and ponderomotive force effects.
• Axial focusing of hot electrons into the target occurs due to magnetic fields.
• Filamentation of hot electrons can occur in moderate Z targets via resistive Weibel-like instability.

Conclusions:

• Engineered hot electron retention, combined with ponderomotive density profile steepening, may reduce hot electron range, benefiting fast ignition.
• Alternatively, uncontrolled retention could hinder deeper energy deposition required for radiography and fast ion generation.