Continuum-based diagnostics of weakly nonideal laser-produced plasmas

Abstract

We have developed a novel diagnostic technique for weakly nonideal laser-produced plasma (LPP) plumes, based entirely on the continuum, and present the result for aluminum plasma. Due to significant self-absorption, the analysis is carried out in close coupling with plasma equilibrium calculations. We first invoke scaling relations linking the time- and position-resolved specific continuum intensity I, integrated over the spectral range of a streak camera, to the local temperature T and pressure p: T=STIα and p=SpIα+β. Inversion of the two-dimensional luminosity profile into the specific continuum intensity profile (three-dimensional) is carried out self-consistently, subject to the 16 independent measurements: target mass loss, energy deposited into the LPP plume and laser beam attenuation at fundamental and its harmonic frequencies, all at four different laser energies. An agreement to within 6.1% of the measurements overall has been achieved with α=0.45±0.03, β=1.0±0.03, ST=0.190±0.003 and Sp=340±5.