Role of spectroscopic diagnostics in studying nanosecond laser-plasma interaction

Abstract

We studied the impact of varying the intensity of Nd:YAG nanosecond 1.06 μm laser radiation on the morphology and internal structure of copper plasma plumes were examined. Standard diagnostic techniques used to deduce axial distributions of electron density and temperature revealed effects of a pronounced plasma screening regime. Methods of fast imaging spectroscopy are used to examine the transition from weak- to high-screening plasma, applying irradiance on the order of 109 W cm-2 in helium atmosphere. Behavior of both ionized and neutral species was observed up to 1 μs after the laser pulse. Showing significant differences with an increase of laser irradiance, the change in plasma propagation mechanisms is attributed to internal shockwave dynamics within the plasma plume. Implications of observed behavior to plasma uniformity can affect diagnostics, and are relevant to both modeling and applications. Graphical abstract: [Figure not available: see fulltext].