Ion Acceleration by the Radiation Pressure of Slow Electromagnetic Wave

TL;DR

This paper investigates ion acceleration via radiation pressure of slow electromagnetic waves, demonstrating velocity limits, instability effects, and energy spectrum broadening in laser-plasma interactions.

Contribution

It introduces the concept that ion velocities are limited by laser group velocity and analyzes instability effects during collisionless shock wave acceleration.

Findings

Ion velocity cannot exceed laser group velocity.

Instabilities cause ion energy spectrum broadening.

Collisionless shock waves facilitate ion acceleration.

Abstract

When the ions are accelerated by the radiation pressure of the laser pulse, their velocity can not exceed the laser group velocity, in the case when it is less than the speed of light in vacuum. This is demonstrated in two cases corresponding to the thin foil target irradiated by a high intensity laser light and to the hole boring by the laser pulse in the extended plasma accompanied by the collisionless shock wave formation. It is found that the beams of accelerated at the collisionless shock wave front ions are unstable against the Buneman-lke and the Weibel-like instabilities which result in the ion energy spectrum broadening.