Calculation of electron density and temperature of plasmas by using new Stark broadening formula of helium lines

• Published in: Physics of plasmas 2019-02, Vol.26 (2)
• Main Authors: Sadeghzadeh Lari, E., Ranjbar Askari, H., Meftah, M. T., Shariat, M.
• Format: Article
• Language: English
• Subjects: Collisions; Electric potential; Electron density; Electron energy; Electrons; Free electrons; Helium; Helium atoms; Mathematical analysis; Neon; Plasma; Plasma jets; Plasma physics; Plasmas (physics)
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.5085050

In this work, three helium lines are considered to find the density and the temperature of the electrons (Ne and Te) in a plasma jet. We have, at first, developed a new formula for Stark broadening through an exact contribution of the weak collisions of the free electrons with helium atoms (He). So, the sum of the weak and strong collision contributions to the spectral broadening is obtained as a function of the electron density Ne and the electron temperature Te: it is called the Stark broadening by the electron collisions with He atoms. By calculating resonance, Doppler, and van der Waals broadenings, measuring instrumental broadening, and using our experimental profiles, we have inferred the value of the full Stark broadening (by ion and electron collisions) for three helium lines (501 nm, 667 nm, and 728 nm). By using a relation between the full Stark broadening and electron collision broadening for each line, we have established a relation between the electron density and the electron temperature of the plasma for each line. The plot of the three corresponding functions Ne(Te) leads to have a good estimation of the electron density Ne and the electron temperature Te. The obtained result for Ne and Te is for a fixed value of the voltage, U, and the frequency, f. Repeated experiments for other values of voltage and frequency give other values of the electron density and the electron temperature.