Investigation of charged particles dynamics along with self-generated electric and magnetic fields in axially resolved laser-induced magnesium plasma

Abstract

Laser ablated Mg plasma was generated by employing Nd-YAG laser (532 nm, 10 ns). Faraday cups with Electric and Magnetic probes have been employedto evaluate axial plasma parameters and Self-Generated Electric and Magnetic Fields (SGEMFs) at various axial distances from target (1 cm to 4 cm) and at various laser irradiances 1.8 GW/cm2 to 4.5 GW/cm2. The evaluated number densities of ions vary from 1.4 × 1013 cm−3 to 6.91 × 1013 cm−3 and electron number densities variation is from 2.38 × 1013 cm−3 to 5.15 × 1013 cm−3. The electron temperature varies from 1.3 eV to 125 eV, whereas, ion kinetic energies vary from 114 eV to 385 eV. Moreover, self-generated electric field variation is from 0.28 V/cm to 20 V/cm and magnetic field is from 978 Gauss to 2628 Gauss. Furthermore, the maxima of ion signal amplitude have been observed at 3 cm distance from target, whereas, electron signals amplitude decreases as Faraday cup to target distance increases. Both evaluated SGEMFs show decreasing trends with increasing target to probe distances and increase with increasing laser irradiance. It is observed that the shape of SGEMFs signals have been significantly affected by increasing laser irradiances and transform from unipolar to dipolar. The charge separation of plasma species, two-electron temperature distribution and bipolar signals of SGEMFs confirm the quadruple distribution of charges in plasma. It uncovers the importance of ion and electron number density gradients in plasma.