Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session PR2: Computational Methods and Modeling for Plasmas |
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Chair: Jong Won Shon, Jusang Engineering Room: Holiday Inn Salon B |
Thursday, October 12, 2006 8:00AM - 8:15AM |
PR2.00001: Revisiting the anomalous skin layer Igor Kaganovich Radio frequency waves do not penetrate into a plasma and are damped within it. The electric field of the wave and plasma current are concentrated near the plasma boundary in a skin layer. Electrons can transport the plasma current away from the skin layer due to their thermal motion. As a result, the width of the skin layer increases when electron thermal velocity is taken into account. This phenomenon is called the anomalous skin effect. The anomalous penetration of the rf electromagnetic field occurs not only for the electric field parallel to the plasma boundary (inductively coupled plasmas) but also for the electric field normal to the plasma boundary (capacitively coupled plasmas) [1]. Recent advances in the nonlinear, nonlocal theory of the anomalous skin layer are reported. It is shown that separating the electric field profile into exponential and non-exponential parts yields an efficient qualitative and quantitative description of the anomalous rf field penetration in inductively coupled plasmas. \newline \newline [1] I. D. Kaganovich, O. V. Polomarov, and C. E. Theodosiou, ``Revisiting the anomalous rf field penetration into a warm plasma,'' to be published in IEEE Trans. Plasma Sci. (2006). [Preview Abstract] |
Thursday, October 12, 2006 8:15AM - 8:30AM |
PR2.00002: Neutral gas depletion through high electron pressures in dense plasmas Deborah O'Connell, Timo Gans, Dragos Crintea, Uwe Czarnetzki, Nader Sadeghi An inductively coupled radio-frequency (rf) magnetic neutral loop discharge (NLD) allows plasma operation at extremely low pressures, down to $10^{-2}$ Pa. In this pressure regime ohmic heating is inefficient and collisionless heating mechanisms become dominant. Temporal signatures in the electron energy distribution function (EEDF) are investigated using phase resolved optical emission spectroscopy (PROES) and Thomson scattering. As expected from global model predictions, both the degree of ionisation and the `electron pressure' strongly increase with decreasing pressure. An interesting feature arises where the electron pressure can exceed the neutral gas pressure resulting in localised depletion of the neutral gas, in particular in the plasma production region around the neutral loop (NL). This depletion of neutral particles is investigated using spatially resolved LIF measurements on argon metastables and TALIF experiments on ground state krypton atoms. Diode laser absorption spectroscopy on metastable argon atoms is used to measure metastable densities and gas temperatures. The ratio of the metastables densities and ground state densities has been found to reflect the electron temperature. [Preview Abstract] |
Thursday, October 12, 2006 8:30AM - 8:45AM |
PR2.00003: A benchmark study of the global model approximation D.D. Monahan, M.M. Turner Global, or volume-averaged, plasma chemistry models have been widely used in low temperature plasma physics. The assumptions and simplifications typically associated with these models severely limits the parameter domain over which they may be applied. Well defined boundaries to these domains, however, do not appear to have been established. Often only minimal model validation is offered in the literature. The aim of this project is to critically evaluate the performance of an elementary global model over a range of parameters and gas compositions by comparing such a model to a set of benchmark particle-in-cell simulations in Ar/O$_2$ mixtures. These simulations cover a wide range of conditions in terms of collisionality, electronegativeity, and negative ion destruction mechanism. It is found, as expected, that the most significant limitation of the model appears to be the oft-used assumption of a Maxwellian electron energy distribution. Adopting the modifications proposed in [1] is shown to be a significant improvement upon this assumption. It is also found that acceptable model-simulation agreement can be obtained without accounting for the complex spatial structures observed in these discharges. \newline \newline [1] Gudmundsson, J.~T., {\it On the effect of the electron energy distribution on the plasma parameters of an argon discharge: a global (volume-averaged) model study}, Plas. Sourc. Sci. Technol., {\bf 10} (2001), 76-81 [Preview Abstract] |
Thursday, October 12, 2006 8:45AM - 9:00AM |
PR2.00004: Simulation of Plasma Spectra Using PrismSPECT Nicolas Pereyra, Joseph MacFarlane, Pamela Woodruff, Igor Golovkin, Ping Wang PrismSPECT is a collisional-radiative spectral analysis code designed to simulate the atomic and radiative properties of LTE and non-LTE plasmas spanning a wide range of conditions. For a grid of user-specified plasma conditions, PrismSPECT computes spectral properties (emission and absorption), ionization fractions, atomic level populations, atomic transition rates, and line intensities and ratios. In designing PrismSPECT, a strong emphasis has been placed on ease of use for setting up problems, monitoring the progress of simulations, and viewing results. The collisional-radiative modeling in PrismSPECT includes: collisional ionization, recombination, excitation, deexcitation, photoionization, stimulated recombination, photoexcitation, stimulated emission, spontaneous decay, radiative recombination, dielectronic recombination, autoionization, and electron capture. Line profiles include Doppler, natural (incl. autoionization contributions), and Stark broadening. Energy levels, cross sections and rate coefficients are based on the ATBASE suite of codes, which incorporates NIST atomic level energies and oscillator strengths when available. [Preview Abstract] |
Thursday, October 12, 2006 9:00AM - 9:15AM |
PR2.00005: Cross-platform, multi-language libraries for ionization and surface interaction effects in plasmas Peter Stoltz, Scott Sides, Nate Sizemore, Seth Veitzer, Miguel Furman, Jean-Luc Vay We are developing a library of numerical algorithms for modeling plasma effects such as ionization, secondary electron production, and ion-surface interaction. The goal is to make this library accessible to a large number of researchers by making it available on multiple computing platforms (Linux, Windows, Mac OS X) and available in multiple computing languages (Fortran, C, Python, Java). We discuss our use of the GNU autotools and the Babel utility to accomplish this cross-platform, multi-language interface. We then discuss application of this library within the WARP particle-in-cell code for modeling effects of ion-induced electrons in the High Current Experiment and within the VORPAL particle-in-cell code for modeling kinetic effects in hollow cathode discharges. [Preview Abstract] |
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