Demonstration of full-scale spatio-temporal diagnostics of solid-density plasmas driven by an ultra-short relativistic laser pulse using an X-ray free-electron laser

TL;DR

This paper demonstrates the first full-scale spatio-temporal diagnostics of solid-density plasmas driven by ultra-short relativistic laser pulses using advanced X-ray free-electron laser techniques, revealing detailed plasma dynamics.

Contribution

It introduces a novel experimental approach combining multiple X-ray diagnostics to observe complex plasma behaviors at nanometer and picosecond scales.

Findings

Observation of preplasma generation with nanometer-scale length

Ultrafast heating and ionization at main pulse arrival

Detection of laser-driven shock waves and surface current dynamics

Abstract

Understanding the complex plasma dynamics in ultra-intense relativistic laser-solid interactions is of fundamental importance to the applications of laser plasma-based particle accelerators, creation of high energy-density matter, understanding of planetary science and laser-driven fusion energy. However, experimental efforts in this regime have been limited by the accessibility of over-critical density and spatio-temporal resolution of conventional diagnostics. Over the last decade, the advent of femtosecond brilliant hard X-ray free electron lasers (XFELs) is opening new horizons to break these limitations. Here, for the first time we present full-scale spatio-temporal measurements of solid-density plasma dynamics, including preplasma generation with tens of nanometer-scale length driven by the leading edge of a relativistic laser pulse, ultrafast heating and ionization at the main pulse arrival, laser-driven blast shock waves and transient surface return current-induced compression dynamics up to hundreds of picoseconds after interaction. These observations are enabled by utilizing a novel combination of advanced X-ray diagnostics such as small-angle X-ray scattering (SAXS), resonant X-ray emission spectroscopy (RXES), and propagation-based X-ray phase-contrast imaging (XPCI) simultaneously at the European XFEL-HED beamline station.