Longitudinal instabilities affecting the moving critical layer laser-plasma ion accelerators

TL;DR

This paper investigates the longitudinal instabilities in laser-driven plasma ion accelerators, analyzing physical processes through theory and simulations to identify methods for stabilizing the acceleration structure and controlling the energy spread of ion beams.

Contribution

It provides a combined analytical and simulation study of key physical processes causing instabilities in moving critical layer accelerators, proposing control measures for improved beam quality.

Findings

Identification of dominant instability mechanisms

Analysis of their interplay affecting energy spectra

Proposed strategies for instability mitigation

Abstract

In this work we analyze the longitudinal instabilities of propagating acceleration structures that are driven by a relativistically intense laser at the moving plasma critical layer [1]. These instabilities affect the energy-spectra of the accelerated ion-beams in propagating critical layer acceleration schemes [2][3]. Specifically, using analytical theory and PIC simulations we look into three fundamental physical processes and their interplay that are crucial to the understanding of energy spectral control by making the laser-plasma ion accelerators stable. The interacting processes are (i) Doppler-shifted ponderomotive bunching [1][4] (ii) potential quenching by beam-loading [2] and (iii) two-stream instabilities. These phenomenon have been observed in simulations analyzing these acceleration processes [5][6][7]. From the preliminary models and results we present in this work, we can infer measures by which these instabilities can be controlled [8] for improving the energy-spread of the beams.