Plasma electron fluid motion and wave breaking near a density transition

Area of Science:

• Plasma physics
• Laser-plasma interactions
• Particle acceleration

Background:

• Investigates electron trapping in plasma wake fields, a key mechanism for particle acceleration.
• Builds upon previous theoretical proposals for density transition-induced trapping.

Purpose of the Study:

• To provide a self-consistent fluid dynamical description of electron trapping in plasma wake fields.
• To analyze the conditions and extent of wave breaking in this trapping mechanism.
• To compare fluid model predictions with particle-in-cell (PIC) simulations.

Main Methods:

• Developed a one-dimensional nonlinear relativistic second-order differential equation for electron fluid velocity.
• Employed numerical integration of the derived equation to explore parameter space.
• Conducted one-dimensional particle-in-cell (PIC) simulations for validation.

Main Results:

• The fluid analysis accurately predicts the onset of wave breaking and particle trapping.
• The downstream extent of wave breaking in the fluid model is not a reliable indicator of the number of trapped particles.
• PIC simulations show trapping of particles upstream of the density transition, which are not captured by the fluid model's wave breaking description.

Conclusions:

• Fluid dynamics offers a valuable framework for understanding wave breaking in plasma wake field electron trapping.
• Discrepancies between fluid and PIC simulations highlight the limitations of the fluid model for predicting trapped particle quantities and behavior.
• Further investigation is needed to fully reconcile fluid and kinetic descriptions of particle trapping in plasma wake fields.