Understanding space plasma through diagnostics and modelling

Abstract

The fourth fundamental state of matter, plasma, is a highly ionized gas composed of neutral atoms, free electrons, and ions. A comprehensive understanding of plasma behavior necessitates accurate measurement of key plasma parameters such as plasma potential, electron and ion densities, and electron temperature. This thesis presents the development of a plasma diagnostics toolkit combining Optical Emission Spectroscopy, often abbreviated as OES, and the Langmuir probe, designed to operate within a custom-fabricated plasma chamber. Air and argon plasmas were generated at varying discharge conditions and characterized using an OES spectrometer. Spectral data were acquired via the software interface integrated with the spectrometer, followed by baseline correction and smoothing to identify peak wavelengths and intensities. These refined spectra enabled the construction of Boltzmann plots, from which the electron temperature (Te) was derived. Electron density (ne) was subsequently calculated using the FWHM and the Stark broadening parameter (ω) of selected emission lines. Furthermore, additional key plasma parameters were computed for a range of pressures and applied voltages. Trends and correlations between these parameters and discharge conditions were analyzed and presented graphically, offering deeper insight into the influence of pressure and voltage on plasma behavior.