Spectroscopic Line Ratio Determination of Electron Density, Electron Temperature, and H$_2$ Dissociation Fraction in PFRC-2 Pulsed Hydrogen Plasmas

The degree of H$_2$ dissociation in a hydrogen plasma affects the relative intensities of H I spectral lines and is therefore an important parameter in the interpretation of H I spectra. Line ratio spectroscopy using an iCCD spectrometer and a high time resolution monochromator is used to determine the electron temperature, electron density, and degree of H$_2$ dissociation in PFRC-II pulsed hydrogen plasmas. Ratios of impurity helium I spectral line intensities yield measurements of the electron temperature and density via a collisional-radiative (CR) model.\footnote{S. Sasaki, S. Takamura, S. Watanabe, S. Masuzaki, T. Kato, and K. Kadota, Review of Scientific Instruments \textbf{67}, 3521 (1996).} Similar CR calculations for hydrogen then relate the observed Balmer line ratio H-$\beta$/H-$\alpha$ to the degree of H$_2$ dissociation.\footnote{T. Fujimoto, K. Sawada, and K. Takahata, Journal of Applied Physics 66, 2315 (1989).} Results are presented at various axial and radial positions in the plasma as parameters such as RF input power, axial magnetic field, and initial gas pressure are varied.