Two-dimensional investigation of characteristics parameters and their gradients for the self-generated electric and magnetic fields of laser-induced zirconium plasma

Abstract

Two-dimensional (2-D) diagnosis of laser-induced zirconium (Zr) plasma has been experimentally performed using the Time-Of-Flight (TOF) method by employing Faraday cups (FCs), and electric and magnetic probes. The characteristic parameters of laser-induced Zr plasma have been evaluated as a function of different laser irradiances ranging from 4.5 to 11.7 GW cm−2 at different axial positions of 1cm–4 cm with a fixed radial distance of 2 cm. A well-supporting correlation between plume parameters and laser-plasma-produced spontaneous electric and magnetic (E and B) fields has been established. The measurements of characteristic parameters and spontaneously induced fields are observed to have an increasing trend with increasing laser irradiance. Whereas, with increasing spatial distances in both axial and radial directions, plasma parameters (electron/ion number density, temperature and kinetic energy) do not show either continuously increasing or decreasing trends due to various kinetic and dynamic processes during spatial evolution of plume. However, the E and B fields are observed to be always diffusing away from the target. The radial component of electron number densities remains higher than the axial number density component, whereas, axial ion number density at all laser irradiances and axial distances remains higher than radial ion number density. The higher axial Self-Generated Electric Field (SGEF) values than radial SGEF are correlated with the effective charge-separation mechanism of electrons and ions. The generation of Self-Generated Magnetic Field (SGMF) is observed dominantly in the radial direction at increasing laser irradiance as compared to the axial one due to the deflection of fast-moving electrons and persistence of Two-Electron Temperature (TET) on the radial axis.