Energy and flux measurements of laser-induced silver plasma ions by using Faraday cup

Abstract

Silver (Ag) plasma has been generated by employing Nd:YAG laser (532 nm, 6 ns) laser irradiation. The energy and flux of ions have been evaluated by using Faraday cup (FC) using time of flight (TOF) measurements. The dual peak signals of fast and slow Ag plasma ions have been identified. Both energy and flux of fast and slow ions tend to increase with increasing irradiance from 7 GW cm−2 to 17.9 GW cm−2 at all distances of FC from the target surface. Similarly a decreasing trend of energies and flux of ions has been observed with increasing distance of FC from the target. The maximum value of flux of the fast component is 21.2 × 1010 cm−2, whereas for slow ions the maximum energy and flux values are 8.8 keV, 8.2 × 1012 cm−2 respectively. For the analysis of plume expansion dynamics, the angular distribution of ion flux measurement has also been performed. The overall analysis of both spatial and angular distributions of Ag ions revealed that the maximum flux of Ag plasma ions has been observed at an optimal angle of ∼15°. In order to confirm the ion acceleration by ambipolar field, the self-generated electric field (SGEF) measurements have also been performed by electric probe; these SGEF measurements tend to increase by increasing laser irradiance. The maximum value of 232 V m−1 has been obtained at a maximum laser irradiance of 17.9 GW cm−2.