Electron density characterization of 27.1 and 50 MHz inductively coupled plasmas by means of Abel corrected Stark broadened Hβ line profiles
Stark broadened profiles of the Hβ line were employed to obtain spatially resolved electron number densities in 27.12 and 50 MHz inductively coupled plasmas emission sources. A computerized system was developed for measuring the Hβ line profile with two stepping motors, which together provided a wavelength scan of the Hβ line profile, as well as a lateral displacement of the plasma image across the entrance slit. This system thus enables the spatially integrated Stark broadened Hβ line profile radiances to be converted to radially corrected profiles by using Abel integral equations. The fractional Stark widths (α1 2) calculated by Griem were used to obtain electron density values from the halfwidths of the radially resolved Hβ line profile. Electron number densities were obtained at various heights and gas flows to characterize the electron number density gradients, which ranged between 1 × 1021 and 5 × 1021 m-3 for these investigations and agree very well with values obtained by methods based on continuum measurements and the Saha-Eggert equation. © 1986.