Dephasing of ion beams as Magnetic Vortex Acceleration regime transitions into a bubble-like field structure

TL;DR

This paper investigates how ion beam dephasing occurs during the transition into a bubble-like magnetic field structure in Magnetic Vortex Acceleration, using 3D simulations to analyze effects of laser contrast and preplasma conditions.

Contribution

It provides new insights into the robustness and efficiency of Magnetic Vortex Acceleration under realistic experimental conditions, including improved scaling laws and the impact of preplasma.

Findings

Preplasma conditions significantly affect ion beam quality.

Laser focal spot size influences acceleration efficiency.

Magnetic vortex structures are stable under various contrast conditions.

Abstract

The interaction of an ultra-intense laser pulse with a near critical density target results in the formation of a plasma channel, a strong azimuthal magnetic field and moving vortices. An application of this is the generation of energetic and collimated ion beams via Magnetic Vortex Acceleration. The optimized regime of Magnetic Vortex Acceleration is becoming experimentally accessible with new high intensity laser beamlines coming online and advances made in near critical density target fabrication. The robustness of the acceleration mechanism with realistic experimental conditions is examined with three-dimensional simulations. Of particular interest is the acceleration performance with different laser temporal contrast conditions, in some cases leading to pre-expanded target profiles prior to the arrival of the main pulse. Preplasma effects on the structure of the accelerating fields is explored, including a detailed analysis of the ion beam properties and the efficiency of the process. Improved scaling laws for the MVA mechanism, including the laser focal spot size effects, are presented.