Composition Determination at High Temperatures by Laser Produced Plasma Analysis

Abstract

Materials in a high temperature condensed phase require new means of characterization. The method of analysis by laser produced plasmas (LPP) combines interaction of a high power laser pulse with the surface in nanosecond time scales and time-and space-resolved detection of the emission spectrum from the plasma plume. In order to meet the requirement that the plasma plume has the same elemental composition as in the condensed phase, a rule of thumb for operation of the laser has been first established in terms of the relationship between the thermal diffusion speed and the rate at which the surface layer is removed by evaporation. This paper describes the physical processes of the laser - matter interaction and the evolution of the plasma plume in time and space, as revealed by experiment and numerical simulation. An account of a new application of the LPP method to compositional analysis of molten metals is presented.