[Characterization of Plasma Induced by Laser Effect on Coal Sample]

Area of Science:

• Plasma Physics
• Laser Spectroscopy
• Materials Science

Background:

• Laser-induced plasma spectroscopy (LIPS) is a powerful tool for elemental analysis.
• Understanding plasma characteristics like temperature and electron density is crucial for accurate LIPS analysis.
• Coal plasma diagnostics present unique challenges due to complex composition and potential self-absorption.

Purpose of the Study:

• To investigate the emission spectrum of laser-induced coal plasma.
• To determine the spatial distribution of plasma temperature and electron density.
• To analyze the influence of self-absorption on spectral line profiles and its implications for diagnostics.

Main Methods:

• Utilizing an optical parametric generator/amplifier (OPG/OPA) pumped by a pulsed Nd:YAG laser (355 nm) as the radiation source.
• Analyzing the emission spectrum of laser-induced coal plasma, focusing on spectral line profiles (Lorenz profile) and Stark broadening.
• Measuring spatial distributions of plasma temperature and electron density through spectral line intensity and Stark broadening.

Main Results:

• Stark broadening was identified as the dominant line widening mechanism.
• Plasma temperature and electron density showed symmetrical distribution vertically and asymmetrical distribution horizontally, peaking at the flame center.
• Self-absorption was observed, particularly at wavelengths near the spectral line center, increasing with laser energy and particle density.

Conclusions:

• Collecting emission spectra from the plasma center is recommended for accurate plasma characteristic diagnosis.
• Selecting spectral lines without self-absorption is essential to ensure higher detection accuracy in laser spectroscopy.
• Laser energy influences particle density, emission intensity, and self-absorption, necessitating careful selection of experimental parameters.