Low-Density Hydrodynamic Plasma Waveguides: Cladding Generation and Gas Jet Development

Meter-scale, low plasma density (∼10¹⁷ cm⁻³) hydrodynamic plasma waveguides generated by Bessel beams have forged a path for development of all-optical laser wakefield acceleration (LWFA) to tens of GeV. At low density, the mechanism and appropriate conditions for development of a well-confining waveguide cladding are of particular interest. Here, we apply a simple scaling model to estimate these conditions and use them to contextualize recent plasma waveguide generation experiments from several groups. We show that plasma waveguide generation initiated in low density gases using a single Bessel beam pulse typically requires an auxiliary laser pulse to generate a well-confining cladding. We present simulations and measurements of low-density optical field ionized plasma channel evolution that confirm the need for such an auxiliary pulse. We also discuss meter-scale supersonic gas jet targets in which waveguides are formed, a key development leading to the recent progress in multi-GeV LWFA.A