The formation of a plasma channel in the optical breakdown of a gas by tubular Bessel beams

The plasma formed by the breakdown of gases (argon was used in the experiments, whereas argon and helium were considered in the calculations) at atmospheric pressure in light beams was studied experimentally and modelled numerically. The field amplitude in these beams was virtually constant in the direction of propagation and described by a high-order Bessel function in the radial direction. The initial stage in the evolution of a spark, when the tubular configuration of the heating-radiation caustic exerts the greatest influence on the characteristics of the plasma channel, was investigated.