Physical mechanism of the transverse instability in radiation pressure ion acceleration

TL;DR

This paper investigates the physical origin of transverse instability in radiation pressure ion acceleration, combining a theoretical model with 2D PIC simulations to explain the instability mechanism and its characteristics.

Contribution

It introduces a theoretical model explaining the transverse instability in RPA, supported by simulations, revealing the coupling between electrons and ions as the core mechanism.

Findings

Density ripples are caused by electron-ion coupling.

The mode structure and growth rates match theoretical predictions.

The model captures the essential physics of target breakup.

Abstract

The transverse stability of the target is crucial for obtaining high quality ion beams using the laser radiation pressure acceleration (RPA) mechanism. In this letter, a theoretical model and supporting two-dimensional (2D) Particle-in-Cell (PIC) simulations are presented to clarify the physical mechanism of the transverse instability observed in the RPA process. It is shown that the density ripples of the target foil are mainly induced by the coupling between the transverse oscillating electrons and the quasi-static ions, a mechanism similar to the transverse two stream instability in the inertial confinement fusion (ICF) research. The predictions of the mode structure and the growth rates from the theory agree well with the results obtained from the PIC simulations in various regimes, indicating the model contains the essence of the underlying physics of the transverse break-up of the target.