Volumetric heating of nanowire arrays to keV temperatures using kilojoule-scale petawatt laser interactions

TL;DR

This study demonstrates the generation of high energy density plasma in nanowire arrays using petawatt laser pulses, revealing keV temperatures sustained for tens of picoseconds through combined experimental and simulation analysis.

Contribution

It introduces a novel combination of experimental streaked spectra and simulations to analyze nanowire array heating and plasma evolution under ultra-high-intensity laser irradiation.

Findings

Three-fold increase in helium-like emission compared to flat foil

Achieved keV temperatures in near-solid-density plasma

Wires explode and collide due to strong electric currents

Abstract

We present picosecond-resolution streaked K-shell spectra from 400 nm-diameter nickel nanowire arrays, demonstrating the ability to generate large volumes of high energy density plasma when combined with the longer pulses typical of the largest short pulse lasers. After irradiating the wire array with 100 J, 600 fs ultra-high-contrast laser pulses focussed to $>10^{20}$ W/cm$^{2}$ at the Orion laser facility, we combine atomic kinetics modeling of the streaked spectra with 2D collisional particle-in-cell simulations to describe the evolution of material conditions within these samples for the first time. We observe a three-fold enhancement of helium-like emission compared to a flat foil in a near-solid-density plasma sustaining keV temperatures for tens of picoseconds, the result of strong electric return currents heating the wires and causing them to explode and collide.