Tracing dynamics of laser-induced fields on ultra-thin foils using complementary imaging with streak deflectometry

TL;DR

This paper investigates the evolution of laser-induced electric and magnetic fields on ultra-thin foils using advanced proton streak deflectometry, combining experimental imaging with analytical and simulation models to understand field dynamics.

Contribution

It introduces a refined proton streak deflectometry technique with complementary imaging configurations and develops models to accurately reproduce experimental field measurements.

Findings

Laser pulse duration affects the dominant force on the proton probe.

Magnetic field polarity at the foil's rear side was unambiguously determined.

Enhanced reproducibility and accuracy due to ultra-high laser contrast.

Abstract

We present a detailed study of the electric and magnetic fields, which are created on plasma vacuum interfaces as a result of highly intense laser-matter-interactions. For the field generation ultra-thin polymer foils were irradiated with high intensity femtosecond and picosecond laser pulses with ultra-high contrast. To determine the temporal evolution and the spatial distribution of these fields the proton streak deflectometry method has been developed further and applied in two different imaging configurations. It enabled us to gather complementary information about the investigated field structure, in particular about the influence of different field components (parallel and normal to the target surface) and the impact of a moving ion front. The applied ultra-high laser contrast significantly increased the reproducibility of the experiment and improved the accuracy of the imaging method. In order to explain the experimental observations, which were obtained by applying ultra-short laser pulses, two different analytical models have been studied in detail. Their ability to reproduce the streak deflectometry measurements was tested on the basis of three-dimensional particle simulations. A modification and combination of the two models allowed for an extensive and accurate reproduction of the experimental results in both imaging configurations. The controlled change of the laser pulse duration from 50 femtoseconds to 2.7 picoseconds led to a transition of the dominating force acting on the probing proton beam at the rear side of the polymer foil. The applied proton deflectometry method allowed for an unambiguous determination of the magnetic field polarity at the rear side of the ultra-thin foil.