Revised, fast, flexible algorithms for determination of electron number densities in plasma discharges

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with two electron number density ( n_e) calculation programs written in Turbo Basic (NNE.EXE) and C language (NE.EXE), data mes ( ^∗.DAT), a text file (NE.WP) with the hard copy paper in WordPerfect 5.1 and a text file (README) for the introduction of the data files and programs. The theoretical aspects and applications of NNE.EXE and NE.EXE are described in the main article for three plasmas having a wide range of electron number density (4 × 10 ¹³ to 1 × 10 ¹⁷ cm ^-3). The descriptions of the procedure, data format, and hardware requirements can be found in the Appendix and the README file. The determination of n_e. is accomplished by least-squares fitting of the entire emission profile or the wing portions of the emission profile of the H _β line (486.13 nm) to the theoretical Stark broadened profiles, compiled at electron temperature 2500, 5000, 10000 and 20000 K. This approach can reduce errors in the determination of n_e owing to the structural dip in the center of the Stark profiles depending on n_e value. The curve-fitting routine employs an interval-halving algorithm to produce new interpolated Stark profiles, reduces number of iterations and time required for calculation, and allows the calculation of n_e to the limits set by instrument spectral resolution and the availability of theoretical spectral data. Additionally, each program provides graphic displays allowing the reader to observe the interpolated Stark profiles, the fitting process, and magnitude of residuals during the course of calculation, and the effects of plasma temperatures and spectral resolution on the estimation of n_e. In addition to H _β, theoretical profiles also are included for H _α and H _γ to illustrate the suitability and drawbacks of these lines for n_e estimation. These programs are extended versions of a program reported earlier in Spectrochimica Acta44B, 175 (1989).