Metastable argon atoms under significant neutral depletion in helicon plasmas by laser-induced fluorescence

• Published in: Current applied physics 2017, 17(10), , pp.1254-1259
• Main Authors: Seo, B.H., Kim, J.H., You, S.J.
• Format: Article
• Language: English
• Subjects: Argon neutral; Helicon plasmas; LIF; Metastable-state; 물리학
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2017.05.010

We study the spatial distribution of the metastable-state argon atoms in high density helicon plasmas by means of laser-induced fluorescence. It is observed that the neutral argon in metastable-state has an anomalous radial distribution in density; it has a caldera-like shape radially, which is rare in typical low-temperature plasmas such as inductively coupled plasmas wherein the density increases toward the discharge center, as previously reported. The formation of the distribution can be explained as it forms by the combined effects of significant neutral depletion in high plasma density, off-axis electron-density distribution, and increasing diffusive loss toward the wall. To establish the assertion with the underlying physics, we calculate a simple global model and obtain the neutral density distribution in metastable-state under various conditions. The calculated results qualitatively agree with the experimental results. •Measurement of neutral Argon in metastable state by means of laser induced fluorescence.•A radial distribution has a ‘caldera-like’ shape due to significant neutral depletion and diffusive loss.•Calculated results of the density using simple global model agree with the physics these are asserted by the authors.