Dependence of radiation decay constant of laser produced copper plasma on focal position

Abstract

Laser-induced copper plasma is investigated experimentally and theoretically. Laser-induced plasma on the surface of the copper sample is generated by focusing a nanosecond (∼7 ns) laser pulse. The experiment is performed in the ambient atmosphere at three different focal positions (lens to sample distances). The main objective of this work is to investigate the effect of the focal position on the radiation decay constant of the plasma. Experimental data are used for estimating the plasma temperature, electron density, ablated mass, and radiation decay constant. It is shown that these parameters essentially depend on the focal position with respect to the sample surface. The theory of relaxation of radiation is considered for the kinetic evolution of the plasma. The results of the theory are compared with the obtained experimental data.