Spectroscopic Study of a Helium Plasma Jet with Hydrocarbon Additives

• Published in: High temperature Vol. 58; no. 3; pp. 309 - 316
• Main Authors: Shavelkina, M. B., Amirov, R. Kh, Kavyrshin, D. I., Chinnov, V. F.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.05.2020; Springer Nature B.V
• Subjects: Acetylene; Additives; Atoms and Molecules in Strong Fields; Balmer series; Carbon; Classical and Continuum Physics; Direct current; Electron density; Electron energy; Emission analysis; Emission spectra; Helium plasma; Heterogeneity; Industrial Chemistry/Chemical Engineering; Laser Matter Interaction; Line spectra; Materials Science; Mathematical analysis; Physical Chemistry; Physics; Physics and Astronomy; Plasma; Plasma Investigations; Plasma jets; Spectroscopic analysis; Swan bands; Temperature
• ISSN: 0018-151X; 1608-3156
• DOI: 10.1134/S0018151X20030165

The results of a spectroscopic study of the conversion of acetylene and methane in a helium plasma jet produced by a direct current plasma torch are presented. The operating mode of the plasma torch corresponds to conditions that provide a high yield of carbon nanostructures. In the emission spectra recorded during the transverse observation of a 20-mm jet section following the outlet of the anode channel of the plasma torch, high-intensity Swan bands of the С 2 molecule are the dominant component in the visible wavelength range. The spectra show atomic hydrogen lines of the HI Balmer series from H α to H ε , numerous CI carbon lines from ultraviolet 247.9 nm to infrared 962–966 nm, and a number of HeI helium lines. The axial temperature values of the plasma jet were spectrally determined by the observed ionized carbon CII lines 283.7 nm, 392.0 and 426.7 nm. A joint analysis of the emission spectra and the mixture composition calculated in the Saha–Boltzmann approximation revealed the nature of the spatial heterogeneity of the studied He : C : H plasma jet. It is manifested by the difference in the electron temperature of the axial region of the jet, which is measured with ionized carbon lines CII ( T e (0) = 12 000–14 000 K) from the vibrational and rotational temperatures of C 2 molecules ( T V = T R ≅ 5000 K) that emit intensely at the jet periphery. The electron density measured along the H β and H γ line widths, which varies in the range of the observed jet region of n e  = (4–2) × 10 16 cm –3 , corresponds to the ionization equilibrium in a plasma He : C : H mixture with an electron temperature close to T e measured by carbon-ion lines.