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Title: Normal and abnormal evolution of argon metastable density in high-density plasmas

Abstract

A controversial problem on the evolution of Ar metastable density as a function of electron density (increasing trend versus decreasing trend) was resolved by discovering the anomalous evolution of the argon metastable density with increasing electron density (discharge power), including both trends of the metastable density [Daltrini et al., Appl. Phys. Lett. 92, 061504 (2008)]. Later, by virtue of an adequate physical explanation based on a simple global model, both evolutions of the metastable density were comprehensively understood as part of the abnormal evolution occurring at low- and high-density regimes, respectively, and thus the physics behind the metastable evolution has seemed to be clearly disclosed. In this study, however, a remarkable result for the metastable density behavior with increasing electron density was observed: even in the same electron density regime, there are both normal and abnormal evolutions of metastable-state density with electron density depending on the measurement position: The metastable density increases with increasing electron density at a position far from the inductively coupled plasma antenna but decreases at a position close to the antenna. The effect of electron temperature, which is spatially nonuniform in the plasma, on the electron population and depopulation processes of Argon metastable atoms with increasingmore » electron density is a clue to understanding the results. The calculated results of the global model, including multistep ionization for the argon metastable state and measured electron temperature, are in a good agreement with the experimental results.« less

Authors:
;  [1];  [2]
  1. Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of)
  2. Department of Physics, Chungnam National University, Daejeon 305-764 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22410354
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANTENNAS; ARGON; ELECTRON DENSITY; ELECTRON TEMPERATURE; METASTABLE STATES; PLASMA DENSITY

Citation Formats

Seo, B. H., Kim, J. H., E-mail: jhkim86@kriss.re.kr, and You, S. J., E-mail: sjyou@cnu.ac.kr. Normal and abnormal evolution of argon metastable density in high-density plasmas. United States: N. p., 2015. Web. doi:10.1063/1.4921213.
Seo, B. H., Kim, J. H., E-mail: jhkim86@kriss.re.kr, & You, S. J., E-mail: sjyou@cnu.ac.kr. Normal and abnormal evolution of argon metastable density in high-density plasmas. United States. doi:10.1063/1.4921213.
Seo, B. H., Kim, J. H., E-mail: jhkim86@kriss.re.kr, and You, S. J., E-mail: sjyou@cnu.ac.kr. Fri . "Normal and abnormal evolution of argon metastable density in high-density plasmas". United States. doi:10.1063/1.4921213.
@article{osti_22410354,
title = {Normal and abnormal evolution of argon metastable density in high-density plasmas},
author = {Seo, B. H. and Kim, J. H., E-mail: jhkim86@kriss.re.kr and You, S. J., E-mail: sjyou@cnu.ac.kr},
abstractNote = {A controversial problem on the evolution of Ar metastable density as a function of electron density (increasing trend versus decreasing trend) was resolved by discovering the anomalous evolution of the argon metastable density with increasing electron density (discharge power), including both trends of the metastable density [Daltrini et al., Appl. Phys. Lett. 92, 061504 (2008)]. Later, by virtue of an adequate physical explanation based on a simple global model, both evolutions of the metastable density were comprehensively understood as part of the abnormal evolution occurring at low- and high-density regimes, respectively, and thus the physics behind the metastable evolution has seemed to be clearly disclosed. In this study, however, a remarkable result for the metastable density behavior with increasing electron density was observed: even in the same electron density regime, there are both normal and abnormal evolutions of metastable-state density with electron density depending on the measurement position: The metastable density increases with increasing electron density at a position far from the inductively coupled plasma antenna but decreases at a position close to the antenna. The effect of electron temperature, which is spatially nonuniform in the plasma, on the electron population and depopulation processes of Argon metastable atoms with increasing electron density is a clue to understanding the results. The calculated results of the global model, including multistep ionization for the argon metastable state and measured electron temperature, are in a good agreement with the experimental results.},
doi = {10.1063/1.4921213},
journal = {Physics of Plasmas},
number = 5,
volume = 22,
place = {United States},
year = {Fri May 15 00:00:00 EDT 2015},
month = {Fri May 15 00:00:00 EDT 2015}
}
  • The effect of argon gas pressure on its metastable density in inductively coupled plasmas (ICPs) is investigated by using the laser-induced fluorescence method. Our results show that the metastable-state density of argon varies with the gas pressure depending on the measurement position; the density decreases with the pressure at a position far from the ICP antenna, whereas it increases with the pressure at a position near the antenna. This contrast in the metastable-state density trend with the pressure is explained by considering the electron temperature variations at the two measurement positions. The theoretical interpretation and calculation using a global modelmore » are also addressed in detail in this paper.« less
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  • The densities of metastable and resonant atom were measured in atmospheric pressure Ar-He surface-wave plasmas. Measurements were performed using an absorption spectroscopy method taking into account the Voigt profiles of the plasma lines. The density values of the argon {sup 3}P{sub 2}, {sup 3}P{sub 0} (metastable atoms) and {sup 3}P{sub 1} (resonant atoms) levels measured in pure argon discharges are in good agreement with those reported in the literature. A drastic decrease of metastable and resonant densities is observed when introducing helium in amounts as low as 2%. The influence of electron density and gas temperature on the population mechanismsmore » (direct electron excitation from the ground state and dissociative recombination) of metastable and resonant atoms is discussed using a simplified theoretical model.« less
  • Recently, an anomalous evolution of argon metastable density with plasma discharge power (electron density) was reported [A. M. Daltrini, S. A. Moshkalev, T. J. Morgan, R. B. Piejak, and W. G. Graham, Appl. Phys. Lett. 92, 061504 (2008)]. Although the importance of the metastable atom and its density has been reported in a lot of literature, however, a basic physics behind the anomalous evolution of metastable density has not been clearly understood yet. In this study, we investigated a simple global model to elucidate the underlying physics of the anomalous evolution of argon metastable density with the electron density. Onmore » the basis of the proposed simple model, we reproduced the anomalous evolution of the metastable density and disclosed the detailed physics for the anomalous result. Drastic changes of dominant mechanisms for the population and depopulation processes of Ar metastable atoms with electron density, which take place even in relatively low electron density regime, is the clue to understand the result.« less
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