Hydrodynamic, Optically-Field-Ionized (HOFI) Plasma Channels

TL;DR

This paper demonstrates the formation of long, low-density plasma channels via hydrodynamic expansion of optically ionized plasma columns, with experiments and simulations showing their potential for high-repetition-rate laser-plasma accelerators.

Contribution

It introduces a method to create long, low-density plasma channels using optical field ionization and hydrodynamic expansion, supported by both simulations and experimental validation.

Findings

Generated 200 mm long plasma channels with low axial density.

Laser energy required is modest, around 1 mJ per cm of channel.

Experimental results confirm simulation predictions of channel properties.

Abstract

We present experiments and numerical simulations which demonstrate that fully-ionized, low-density plasma channels could be formed by hydrodynamic expansion of plasma columns produced by optical field ionization (OFI). Simulations of the hydrodynamic expansion of plasma columns formed in hydrogen by an axicon lens show the generation of \unit[200]{mm} long plasma channels with axial densities of order $n_e(0) = 1 \times 10^{17} cm^{-3}$ and lowest-order modes of spot size $W_M \approx 40 \mu m$. These simulations show that the laser energy required to generate the channels is modest: of order 1 mJ per centimetre of channel. The simulations are confirmed by experiments with a spherical lens which show the formation of short plasma channels with $1.5 \times 10^{17}cm^{-3} \lesssim n_e(0) \lesssim 1 \times 10^{18} cm^{-3}$ and $61 \mu m \gtrsim W_M \gtrsim 33 \mu m$. Low-density plasma channels of this type would appear to be well-suited as multi-GeV laser-plasma accelerator stages capable of long-term operation at high pulse repetition rates.