# Low-Density Hydrodynamic Optical-Field-Ionized Plasma Channels Generated With An Axicon Lens

## TL;DR

This paper demonstrates the creation and control of low-density hydrodynamic plasma channels using an axicon lens, enabling effective guiding of high-intensity laser pulses for potential applications in multi-GeV laser wakefield accelerators.

## Contribution

It introduces a novel method to generate and control low-density HOFI plasma channels with an axicon lens, achieving high-quality laser guiding over multiple Rayleigh ranges.

## Key findings

- Achieved on-axis electron densities as low as 1.5×10^{17} cm^{-3}.
- Demonstrated reproducible guiding over more than 14 Rayleigh ranges.
- Controlled channel parameters via initial pressure and delay adjustments.

## Abstract

We demonstrate optical guiding of high-intensity laser pulses in long, low density hydrodynamic optical-field-ionized (HOFI) plasma channels. An axicon lens is used to generate HOFI plasma channels with on-axis electron densities as low as $n_e(0) = 1.5\times 10^{17}\, \mathrm{cm}^{-3}$ and matched spot sizes in the range $ 20 \mu \mathrm{m} \lesssim W_M \lesssim 40 \mu \mathrm{m}$. Control of these channel parameters via adjustment of the initial cell pressure and the delay after the arrival of the channel-forming pulse is demonstrated. For laser pulses with a peak axial intensity of $4 \times 10^{17}\, \mathrm{W\,cm}^{-2}$, highly reproducible, high-quality guiding over more than 14 Rayleigh ranges is achieved at a pulse repetition rate of 5 Hz, limited by the available channel-forming laser and vacuum pumping system. Plasma channels of this type would seem to be well suited to multi-GeV laser wakefield accelerators operating in the quasi-linear regime.