Time-resolved study of holeboring in realistic experimental conditions

J Hornung,V Bagnoud,M Zepf,S Roeder,D Bertini,Y Zobus,A Kleinschmidt

doi:10.1038/s41467-021-27363-9

Abstract

The evolution of dense plasmas prior to the arrival of the peak of the laser irradiation is critical to understanding relativistic laser plasma interactions. The spectral properties of a reflected laser pulse after the interaction with a plasma can be used to gain insights about the interaction itself, whereas the effect of holeboring has a predominant role. Here we developed an analytical model, describing the non-relativistic temporal evolution of the holeboring velocity in the presence of an arbitrary overdense plasma density and laser intensity profile. We verify this using two-dimensional particle-in-cell simulations, showing a major influence on the holeboring dynamic depending on the density profile. The influence on the reflected laser pulse has been verified during an experiment at the PHELIX laser. We show that this enables the possibility to determine the sub-micrometer scale length of the preplasma by measuring the maximum holeboring velocity and acceleration during the laser-plasma interaction.

Highlights

The evolution of dense plasmas prior to the arrival of the peak of the laser irradiation is critical to understanding relativistic laser plasma interactions
To improve our understanding of the holeboring dynamics, we developed an analytical description for the holeboring velocity v(t) in the presence of an arbitrary plasma density profile ne(x, t) at the interaction point, whose position defines the critical surface
The necessity to account for an exponential density profile has been discussed by Kemp et al.[21] and used to calculate the position of the critical surface during the interaction, which has been used by Iwata et al.[20] to calculate the holeboring duration and the plasma density cutoff

Summary

Introduction

The evolution of dense plasmas prior to the arrival of the peak of the laser irradiation is critical to understanding relativistic laser plasma interactions. This requires the initial plasma parameters to be treated as a simulation input This ad-hoc treatment is the response to the temporal contrast of the laser, that causes the light intensity to reach the ionization threshold at the target surface tens of picoseconds to a few nanoseconds ahead of the pulse peak, and to trigger an uncontrolled preplasma expansion. This uncertainty of the input state has long been considered one of the key reasons for the discrepancy between the predictions given by the PIC codes and the experimental observations[8]. This in turns slows down the holeboring velocity and a commensurate hole boring time is analytically derived

Methods

Results

Conclusion