Linear discriminant analysis as an alternative method to investigate the interaction of a 1064 nm CW laser light with a cold inductively-coupled plasma

TL;DR

This study investigates the interaction of 1064 nm laser light with inductively-coupled plasma using experimental, theoretical, and linear discriminant analysis methods, revealing how laser power influences plasma properties and spectral features.

Contribution

It introduces the application of linear discriminant analysis to plasma spectra to analyze plasma oscillations and structures under laser interaction, providing new insights into plasma behavior.

Findings

Absorption coefficients decrease with increasing laser power.

Laser interaction induces Whistler mode plasma structures.

Electron temperature increases slightly with laser power.

Abstract

In this paper, the interaction of a 1064 nm continuum-wave laser with inductively-coupled plasma generated in a fluorescent light bulb has been studied both experimentally and theoretically. The absorption coefficients pertaining to the plasma medium were obtained for different power measurements. The results indicate that absorption coefficients decrease with the increase in laser power. The UV-Vis spectra of mercury plasma were recorded by the charge-coupled spectrometer device at different power levels of laser. The linear discriminant analysis (LDA) of plasma spectra reveals the plasma ion and electron oscillations. Fourier series modeling of electron oscillation results the Whistler mode frequency of wpe= 0.16 kHz with a density of ne=3.9x1013 cm^(-3). 3D representation of LDA coefficients shows that the increase of laser power leads the plasma species to form in Whistler mode structures. Plasma electron temperatures ( e T ) was inferred from the SPARTAN non-local thermal equilibrium (non-LTE) spectral code, and they were about 0.6 eV in the absence of laser light. However, there was a 0.05 eV increase in electron temperature when the laser power was absorbed by the plasma. Electron temperatures slightly increased with the increase in the power levels, which in turn resulted in smaller absorption coefficients since the absorption coefficients scales with Te^(-3/2).