Theoretical Investigation of Z-Pinch Ar-Plasma Waveguide in a Millimeter-Scale Cross Section Capillary

Abstract

Theoretical investigation of the transient Z-pinch Ar-plasma waveguide was conducted on CO2-laser pulse with a central wavelength of $10.6~\mu \text{m}$ and an input peak intensity of $1.3\times 10^{15}$ W/cm2. The main plasma variables of the fast Z-pinch discharge were obtained from a 1-D magnetohydrodynamic model. Simulation showed that the guiding channel exists for only a few nanoseconds and occurs far from capillary wall, which makes possible pure plasma guiding. In terms of laser-driven plasma wakefield accelerators, the Z-pinch waveguide is able to extend the acceleration length over the whole capillary, assuming that a single-mode transmission takes place. In order to quantify such ability of the channel, a correlation coefficient was introduced and computed at different input beam spot sizes. As a result, an optimal beam spot size was determined by taking maximum of time average of correlation coefficient over the channel lifetime. At the end of the channel existence, a repetitive focusing and defocusing pattern was observed with significant intensity increase at the focal points. This property offers an alternative regime of waveguiding.