Radiation Pressure-Driven Plasma Surface Dynamics in Ultra-Intense Laser Pulse Interactions with Ultra-Thin Foils

Bruno Gonzalez-Izquierdo,Remi Capdessus,Steve Hawkes,John Mccreadie,Nicola Booth,Paul Mckenna,Martin King,Rachel Dance,David Neely,Nicholas Butler,Robbie Wilson,Marco Borghesi,James Green,Ross Gray

doi:10.3390/app8030336

Bruno Gonzalez-Izquierdo, Remi Capdessus + Show 12 more

Open Access

https://doi.org/10.3390/app8030336

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Abstract

The dynamics of the plasma critical density surface in an ultra-thin foil target irradiated by an ultra-intense (∼6 × 10 20 Wcm − 2 ) laser pulse is investigated experimentally and via 2D particle-in-cell simulations. Changes to the surface motion are diagnosed as a function of foil thickness. The experimental and numerical results are compared with hole-boring and light-sail models of radiation pressure acceleration, to identify the foil thickness range for which each model accounts for the measured surface motion. Both the experimental and numerical results show that the onset of relativistic self-induced transparency, in the thinnest targets investigated, limits the velocity of the critical surface, and thus the effectiveness of radiation pressure acceleration.

Highlights

Significant progress has been made over the past decade in elucidating the physics of ultra-intense laser pulse interactions with solid targets
We present an experimental characterization of the movement of the plasma critical density surface (PCDS) in response to ultra-intense laser radiation, in target foils ranging in thickness from tens to hundreds of nanometres
Simulations were performed using the fully relativistic 2D EPOCH PIC code [29] to investigate how the PCDS dynamics differ over a range of target thicknesses

Summary

Introduction

Significant progress has been made over the past decade in elucidating the physics of ultra-intense laser pulse interactions with solid targets. The recession velocity of the plasma critical density surface (PCDS) in this mechanism is recognized conventionally as the hole-boring velocity This velocity is well described analytically in 1D (spatial) interactions, for relativistic laser intensities, as [21,22]: vhb. The mode of RPA for which the laser pressure is able to push all of the plasma electrons from across the target thickness (in the region of the most intense part of the laser focus) is known as light sail (LS) [23,24]. We present an experimental characterization of the movement of the PCDS in response to ultra-intense laser radiation, in target foils ranging in thickness from tens to hundreds of nanometres This is based on measurements of the degree of red-shift in back-reflected second harmonic radiation produced at the laser focus. The thickness ranges for which distinct laser-plasma interaction regimes, corresponding to HB-dominant, LS-dominant and the onset of RSIT, occur are determined

Experimental Results

PIC Simulation Results

Comparison of Results

Discussion