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Eun Ha Choi - One of the best experts on this subject based on the ideXlab platform.

Guangsup Cho - One of the best experts on this subject based on the ideXlab platform.

A Gleizes - One of the best experts on this subject based on the ideXlab platform.

  • Net Emission Coefficient for CO–H2 thermal plasmas with the consideration of molecular systems
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2015
    Co-Authors: T. Billoux, Yann Cressault, A Gleizes
    Abstract:

    This paper deals with the calculation of net Emission Coefficients (NECs) for CO–H2 thermal plasmas. This task required the elaboration of a complete spectroscopic database including atoms and molecules formed by carbon, oxygen and hydrogen elements. We have used a systematic line by line method to calculate all the main radiative contributions which are the atomic and molecular continua, the atomic lines and the molecular (diatomic and polyatomic) lines. The main diatomic electronic systems for CO–H2 plasmas and the triatomic molecular bands were considered. We present some variations of the net Emission Coefficient versus temperature, for various pressures and for two relative proportions of the components. The role of the diatomic molecules is important at temperatures lower than 5000 K whereas the net Emission Coefficient presents an unusual peak at temperature around 1000 K, due to the presence of the CO2 molecule presenting a strong infrared radiation. Finally, the results show that the NEC slightly depends on the relative proportion of CO and H2.

  • net Emission Coefficient of co2 cu thermal plasmas role of copper and molecules
    Journal of Physics: Conference Series, 2012
    Co-Authors: T. Billoux, Yann Cressault, V Boretskij, A Veklich, A Gleizes
    Abstract:

    The present work was conducted to calculate the radiative transfer in CO2–Cu mixtures at atmospheric pressure. The plasma is supposed to be in local thermodynamic equilibrium (LTE) for temperatures between 500 and 30000 K. In the first part of the work, we briefly present the plasma composition. The second part is devoted to the various mechanisms responsible for the radiation (atomic continuum, molecular continuum, atomic lines and molecular bands). A particular attention is paid to the radiation of molecular bands. These radiative properties are then introduced in the net Emission Coefficient (NEC) which is used to estimate the radiation in an isothermal and homogeneous medium. Finally, some results are proposed for various concentrations of copper and different plasma sizes. For optically thin plasmas, the radiation of molecular bands and metallic vapors strongly increase the NEC at low temperature. For higher plasma sizes, the copper lines do not only have high intensities but are also strongly self-absorbed contrarily to the radiation of the molecular bands which becomes the major part, indicating that we must not neglect their contribution in the total radiation.

  • calculation of the net Emission Coefficient of an air thermal plasma at very high pressure
    Journal of Physics: Conference Series, 2012
    Co-Authors: T. Billoux, Yann Cressault, Ph Teulet, A Gleizes
    Abstract:

    The aim of this paper is to present an accurate evaluation of the phenomena appearing for high pressure air plasmas supposed to be in local thermodynamic equilibrium (LTE). In the past, we already calculated the net Emission Coefficient for air mixtures at atmospheric pressure and for temperatures up to 30kK (molecular contribution being restricted to 10kK). Unfortunately, the existence of high pressures does not allow us to use this database due to the non-ideality of the plasma (Viriel and Debye corrections, energy cut-off ...), and due to the significant shifts of molecular reactions towards upper temperatures. Consequently, this paper proposes an improvement of our previous works with a consideration of high pressure corrections in the composition algorithm in order to take into account the pressure effects, and with a new calculation of all the contributions of the plasma radiation (atomic lines and continuum, molecular continuum, and molecular bands) using an updated database. A particular attention is paid to calculate the contribution of all the major molecular band systems to the radiation: O2 (Schumann–Runge), N2 (VUV, 1st and 2nd positive), NO (IR, β, γ, δ, ) and N2+ (1st negative and Meinel). The discrete atomic lines and molecular bands radiation including the overlapping are calculated by a line-by-line method up to 30kK and 100 bar. This updated database is validated in the case of optically thin plasmas and pressure of 1bar by the comparison of our integrated Emission strength with the published results. Finally, this work shows the necessity to extend the molecular radiation database up to 15kK at high pressure (bands and continuum) since their corresponding contributions could not be neglected at high temperature.

  • net Emission Coefficient of air thermal plasmas
    Journal of Physics D, 2002
    Co-Authors: Y Naghizadehkashani, Yann Cressault, A Gleizes
    Abstract:

    We have calculated the net Emission Coefficient of air plasmas at atmospheric pressure in the temperature range between 300 and 40?000?K, in the assumption of local thermodynamic equilibrium and isothermal plasmas. This calculation takes into account the radiation due to the atomic continuum, the molecular continuum, the molecular bands (several systems for O2, N2, NO and N2+) and the atomic lines. Special attention has been devoted in this paper to the description of the molecular bands radiation. The results show that in the high temperature range where molecules are dissociated, the radiation properties of air plasmas are mainly due to those of nitrogen plasmas, the resonance atomic lines playing an important role in spite of their strong self-absorption. At low temperature (T<6000?K) the role of the molecular bands of oxygen (O2) and NO is predominant.

  • Net Emission Coefficient of air thermal plasmas
    Journal of Physics D: Applied Physics, 2002
    Co-Authors: Y Naghizadeh-kashani, Yann Cressault, A Gleizes
    Abstract:

    We have calculated the net Emission Coefficient of air plasmas at atmospheric pressure in the temperature range between 300 and 40?000?K, in the assumption of local thermodynamic equilibrium and isothermal plasmas. This calculation takes into account the radiation due to the atomic continuum, the molecular continuum, the molecular bands (several systems for O2, N2, NO and N2+) and the atomic lines. Special attention has been devoted in this paper to the description of the molecular bands radiation. The results show that in the high temperature range where molecules are dissociated, the radiation properties of air plasmas are mainly due to those of nitrogen plasmas, the resonance atomic lines playing an important role in spite of their strong self-absorption. At low temperature (T

Jae Yong Lim - One of the best experts on this subject based on the ideXlab platform.

  • Work function of MgO single crystals from ion-induced secondary electron Emission Coefficient
    Journal of Applied Physics, 2003
    Co-Authors: Jae Yong Lim, Jae Won Cho, Seung Oun Kang, Guangsup Cho, Han Sup Uhm, Eun Ha Choi
    Abstract:

    The work functions φω of MgO single crystals with its respective orientation (111), (200), and (220) have been investigated from their ion-induced secondary electron Emission Coefficient γ, respectively, using various ions with different ionization energies in a γ-focused ion beam system. The work function φω for MgO single crystal with (111) orientation has the lowest value, 4.22 eV, whereas it is 4.94 eV for (200) and the highest value is 5.07 eV for (220). These work functions of MgO single crystals can explain the nonzero values of the ion-induced secondary electron Emission Coefficient γ for Xe+ ions, whose ionization energy is 12.13 eV.

  • influence of vacuum annealing process on the secondary electron Emission Coefficient γ from a mgo protective layer
    Japanese Journal of Applied Physics, 2001
    Co-Authors: Jinman Jeoung, Jae Yong Lim, Guangsup Cho, Young-guon Kim, Yoonho Seo, Eun Ha Choi
    Abstract:

    The secondary electron Emission Coefficient (γ) of vacuum-annealed MgO films has been investigated using a γ-focused ion beam (γ-FIB) system. The vacuum-annealed MgO films have been found to have higher γ values from 0.05 to 0.12 than those from 0.03 to 0.06 for as-deposited MgO films for operating Ne+ ions whose acceleration voltages ranged from 50 V to 200 V. It is shown that the γ for the as-deposited MgO protective layer is significantly decreased by the influence of holding in air since the hydroxyl OH groups are absorbed onto the MgO surface from the atmospheric air. It is also observed that the secondary electron Emission Coefficient γ for the vacuum-annealed MgO protective layer is less influenced by holding in air than that for the as-deposited MgO protective layer. Based on these findings, it is concluded that the vacuum-annealed MgO protective layer plays an important role in lowering the firing voltage in alternating current-plasma display panel (AC-PDP) compared with the as-deposited MgO protective layer or the as-deposited MgO protective layer held in air.

  • Ion-Induced Secondary Electron Emission Coefficient(γ)of Bulk-MgO Single Crystals
    Japanese Journal of Applied Physics, 2000
    Co-Authors: Daeil Kim, Jae Yong Lim, Guangsup Cho, Young-guon Kim, Choon-woo Lee, Eun Ha Choi
    Abstract:

    The ion induced secondary electron Emission Coefficient ? of bulk-MgO single crystal has been measured by the ?-focused ion beam system. It is found that the bulk-MgO single crystal with (111) orientation has the highest ? from 0.08 up to 0.21, and the ? values are in the order of the crystallinities, (111) > (200) > (220) for operating Ne+ ions ranging from 50 eV to 300 eV in this experiment. These results are consistent with our previous reports for MgO protective layers with respective orientations of (111), (200), and (220).

  • Secondary electron Emission Coefficient of a MgO single crystal
    Journal of Applied Physics, 1999
    Co-Authors: Eun Ha Choi, Jae Yong Lim, Young-guon Kim, Daeil Kim, Choon-woo Lee, Guangsup Cho
    Abstract:

    The secondary electron Emission Coefficient γ of different MgO single crystal has been measured by γ-focused ion beam system. It is found that the MgO single crystal with (111) orientation has the highest γ from 0.08 up to 0.21, while from 0.06 to 0.19 for (200) and from 0.05 to 0.15 for (220) orientation for operating Ne+ ions ranging from 50 to 300 eV throughout this experiment. It is also found that these observations can be explained by work functions, which are dependent on the crystal orientations of MgO.

  • measurement of secondary electron Emission Coefficient γ of mgo protective layer with various crystallinities
    Japanese Journal of Applied Physics, 1998
    Co-Authors: Eun Ha Choi, Jae Yong Lim, Guangsup Cho, Young-guon Kim, Daeil Kim, Jingoo Kim, Seung Oun Kang
    Abstract:

    The secondary electron Emission Coefficient γ of a MgO protective layer with various crystallinities has been successfully measured by the γ-focused ion beam system with complete elimination of the charge accumulation problem by scanning-area adjustment techniques. It is found that the (111) surface has the highest γ from 0.14 to 0.26 in comparison with the other films with (200) and (220) crystallinities for operating Ne+ ions, while ranged from 0.03 to 0.24 for Ar+ ions, under operating ion energies from 50 eV to 500 eV throughout this experiment. These observations explain why the (111) crystallinity of the MgO protective layer plays an important role in lowering the firing voltages in AC plasma display panel compared to the films with other crystallinities.

A Von Keudell - One of the best experts on this subject based on the ideXlab platform.

  • secondary electron Emission Coefficient of c h and si c thin films and some relations to their morphology and composition
    Diamond and Related Materials, 1996
    Co-Authors: S Groudevazotova, W Jacob, A Von Keudell
    Abstract:

    A complex investigation of the secondary electron Emission Coefficient (SEEC) of two types of carbon containing thin film materials, which are among potential candidates for anti-multi-pactoring (AMP) coatings in high frequency devices, such as HF waveguides used for plasma heating in fusion experiments, has been performed. Relations between the dependencies of the SEEC on the energy E and the angle of incidence of the primary electron beam ϑ and other thin film characteristics such as morphology, composition and thermal stability have been established. As a result, the conditions for plasma enhanced chemical vapor deposition of thermally stable C:H films with a SEEC<1 were determined. In addition, it was found that the Si:C films obtained by d.c. magnetron co-sputtering have, for all investigated energies E and angles ϑ, before and after annealing, a SEEC very close to unity and are interesting new candidates for AMP-coatings.