Elongated long-lived jet of dense plasma produced by a hollow laser beam

Abstract

Numerical simulation of the dynamics of plasma jets planned for use for the initiation of vacuum pinch discharges has been carried out. Jets of the "laser-metal-plasma-liner"type are created by laser beams with different spatial intensity distributions, which irradiate targets of various configurations. The three variants of plasma-jets formation are considered: Irradiation of a target by (I) a Gaussian beam from a neodymium laser, (II) the same Gaussian beam incident on a hole in the target, and (III) a beam with the intensity distribution of the Laguerre-Gaussian mode. The dynamics of spatial distributions of the electron density, jet plasma temperatures, and the target mass ablated by laser radiation is calculated. It is shown that for quite moderate laser beam energies and intensities ∼400 mJ and ∼109 W/cm, respectively, in the second and third cases, jets are produced with the lifetime of a few tens of nanoseconds and the maximum density ∼1019 and 101cm-3, respectively. The use of such jets can increase the pinching efficiency and improve plasma parameters in laser-induced discharges.