Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session QR1: Plasma Modeling and Simulations II |
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Chair: Timo Gans, University of York, Department of Physics Room: State EF |
Thursday, November 6, 2014 3:30PM - 3:45PM |
QR1.00001: RF plasma conductivity in the CERN Linac4 H$^{-}$ ion source, comparison of simulations and measurements Stefano Mattei, Shintaro Mochizuki, Kenjiro Nishida, Takanori Shibata, Jacques Lettry, Akiyoshi Hatayama, Minh Quang Tran CERN Linac4 H$^{-}$ ion source is a Radio Frequency Inductively Coupled Plasma (RF-ICP) ion source. A solenoid antenna of 4 to 6 turns heats the plasma at a frequency of 2 MHz, in pulses of 0.5 ms and with a repetition rate of 0.8 to 2 Hz. In order to investigate the underlying plasma physics we have developed a Particle-In-Cell Monte Carlo Collision (PIC-MCC) code with the long-term goal to optimize the ion source operational parameters and geometry. This paper presents the determination of the complex plasma conductivity based on the PIC-MCC simulations. The resistive and reactive components of the plasma conductivity are computed as the proportionality factor between the RF electric field and the resulting plasma current. We present a parametric investigation as a function of the antenna current, gas pressure and antenna geometry. The simulation results, corresponding to the Linac4 ion source, are compared to the time-resolved optical emission photometry measurements of the Balmer lines obtained on a dedicated ion source test stand. [Preview Abstract] |
Thursday, November 6, 2014 3:45PM - 4:00PM |
QR1.00002: A Fast Four Fluid Model of Electronegative Plasmas Including Non-Isothermal Neutrals Andrew Hurlbatt, Timo Gans, Deborah O'Connell A novel semi-analytical fluid model has been developed of a four component plasma consisting of positive ions, negative ions, non-maxwellian electrons and non-isothermal neutrals. The four dominant interspecies reactions are considered, as well as elastic collisions between charged and neutral species. The model is based on an idealised RF discharge with an infinite planar geometry, and provides time averaged spatial profiles of species densities and fluxes, as well as neutral gas temperature, within the plasma bulk and presheath. Due to the combination of boundary conditions and normalisations, only the mean electron energy and the relative electron density are required as input parameters. The pressure length product of the system is given as an output, meaning the model can be scaled to any plasma discharge sharing geometrical characteristics. Despite the increased complexity and reduced assumptions compared with other similar electronegative models, analyticity is maintained until the point of spatial integration. This means the computation time is on the order of seconds, allowing the detailed investigation of discharge properties on phenomena such as Neutral Gas Depletion and electronegative to electropositive transitions over large regions of parameter space. [Preview Abstract] |
Thursday, November 6, 2014 4:00PM - 4:15PM |
QR1.00003: Uncertainty and error in complex plasma chemistry models Miles Turner Plasma chemistry models commonly contain hundreds if not thousands of parameters, in the way of rate constants and other related coefficients. None of these parameters is exactly known. Moreover, in modern models, the parameters have often been transmitted from the primary data sources by complex and error prone routes. Consequently, typical plasma chemistry models embody unavoidable uncertainty, because of inexact knowledge of the parameters, and some margin of avoidable error, because of faulty transmission. This paper discusses a model for helium/oxygen mixtures (a moderately complex model with some 350 reactions), in which all the the rate constants have been traced to primary sources, with the initial aim of determining the uncertainty associated with each parameter. This data is then used in a Monte Carlo procedure to investigate the resulting uncertainty in the model predictions. Uncertainty is found to be unequally distributed across the model outputs, but for some results it is a factor of several or more. This certainly needs to be considered when comparing model calculations with experiments, or deciding whether conclusions drawn from the model predictions are robust. The process of tracing the sources for the rate constants shows that some of them have been polluted by various types of error. Some examples will be discussed. [Preview Abstract] |
Thursday, November 6, 2014 4:15PM - 4:30PM |
QR1.00004: Development, Verification and Validation of VizArc: a General-Purpose Thermal Plasma Simulation Tool Shankar Mahadevan, Doug Breden, Laxminarayan Raja This work describes a recently developed general-purpose simulation tool (VizArc) for computational modeling of thermal (arc) plasmas. These plasmas typically exist in systems where the pressures range from 0.1-10 atm and with temperatures ranging from about 1000 K to $\sim$10,000's K. VizArc solves a coupled set of non-linear governing equations that describe physical and chemical phenomena in multi-species, single-temperature, quasi-neutral plasma. Governing equations for the flow and electromagnetic quantities in the gas and heat transfer in solids are included. Applications include the modeling of spark discharges, HID lamps, circuit breakers and welding/spray coating. Verification and validation, which are essential aspects of computational code development, are discussed. The steps involved in verification and validation of the new model are described, including component-wise verification, a grid convergence study, parallel implementation verification, and comparison of model results with experimental results from the literature. [Preview Abstract] |
Thursday, November 6, 2014 4:30PM - 4:45PM |
QR1.00005: An Analytical Study of the Mode Propagation along the Plasmaline Daniel Szeremley, Ralf Peter Brinkmann, Thomas Mussenbrock, Denis Eremin The market shows in recent years a growing demand for bottles made of polyethylene terephthalate (PET). Therefore, fast and efficient sterilization processes as well as barrier coatings to decrease gas permeation are required. A specialized microwave plasma source -- referred to as the plasmaline -- has been developed to allow for treatment of the inner surface of such PET bottles The plasmaline is a coaxial waveguide combined with a gas-inlet which is inserted into the empty bottle and initiates a reactive plasma. To optimize and control the different surface processes, it is essential to fully understand the microwave power coupling to the plasma inside the bottle and thus the electromagnetic wave propagation along the plasmaline. In this contribution, we present a detailed dispersion analysis based on an analytical approach. We study how modes of guided waves are propagating under different conditions (if at all). The analytical results are supported by a series of self-consistent numerical simulations of the plasmaline and the plasma. [Preview Abstract] |
Thursday, November 6, 2014 4:45PM - 5:00PM |
QR1.00006: Self-consistent simulation of a microwave coaxial plasma waveguide Rochan Upadhyay, Laxminarayan Raja Microwave discharges are typically useful for generating high density, non-equilibrium plasmas at relatively low electron temperature. Recently there has been much interest in Coaxial Plasma Waveguides (CPW) for large area deposition and etching. In a CPW, microwave propagates between a metallic or dielectric surface and a plasma that acts as an outer conductor. The plasma is sustained by surface wave heating due to the microwave propagating in the waveguide. Most studies of this phenomenon have focused on understanding of the electromagnetic surface wave, its dispersion characteristics and power deposition. The plasma is typically modelled as quasi-neutral and sheath effects are either neglected or represented using simplified analytical models. This approach usually precludes the analysis of important effects like self-bias, imposed DC or RF bias on the electrodes, electrostatic waves and the influence of sheath voltage on charged species transport and/or reaction rates. In this study we simulate a CPW using a fully self-consistent model. The model uses the electrostatic and magnetic vector potential equations that are fully coupled with the plasma governing equations to model the electromagnetic effects. This allows us to study sheath effects in conjunction with the surface wave phenomena at microwave frequencies. We compare results with a simplified model that assumes a quasi-neutral plasma that neglects the sheath. We also discuss the range of applicability of simplified models. [Preview Abstract] |
Thursday, November 6, 2014 5:00PM - 5:15PM |
QR1.00007: Electron acceleration due to the two-stream instability of ion and electron beams propagating in background plasma Igor Kaganovich, Dmytro Sydorenko Intense electron or ion beams propagating in plasmas are subject to the two-stream instability, which leads to a slowing down of the beam particles, acceleration of the plasma particles, and transfer of the beam energy to the plasma particles and wave excitations. Making use of the particle-in-cell codes EDIPIC and LSP, we have simulated two-stream instability interactions over a wide range of beam and plasma parameters. Typically, the instability saturates due to nonlinear wave-trapping effects of either the beam particles or plasma electrons. The saturation due to nonlinear wave-trapping effects limits the ``mixing'' in phase-space and may produce coherent structures in the electron velocity distribution function. For the case of an electron beam, simulations show that the two-stream instability is intermittent, with quiet and active periods. During the active periods of the two-stream instability, the beam interacts with the plasma most intensively at locations where the global frequency of the instability matches the local electron plasma frequency. These intense localized plasma oscillations produce peaks in the velocity distribution function similar to the ones measured in the experiment [1]. \\[4pt] [1] L. Xu et al., Appl. Phys. Lett. 93, 261502 (2008). [Preview Abstract] |
Thursday, November 6, 2014 5:15PM - 5:30PM |
QR1.00008: Transport and radiation in complex LTE mixtures Jesper Janssen, Kim Peerenboom, Jos Suijker, Mykhailo Gnybida, Jan van Dijk Complex LTE mixtures are for example encountered in re-entry, welding, spraying and lighting. These mixtures typically contain a rich chemistry in combination with large temperature gradients. LTE conditions are also interesting because they can aid in the validation of NLTE algorithms. An example is the calculation of transport properties. In this work a mercury free high intensity discharge lamp is considered. The investigation focusses on using salts like InI or SnI as a buffer species. By using these species a dominant background gas like mercury is no longer present. As a consequence the diffusion algorithms based on Fick's law are no longer applicable and the Stefan-Maxwell equations must be solved. This system of equations is modified with conservation rules to set a coldspot pressure for saturated species and enforce the mass dosage for unsaturated species. The radiative energy transport is taken into account by raytracing. Quantum mechanical simulations have been used to calculate the potential curves and the transition dipole moments for indium with iodine and tin with iodine. The results of these calculations have been used to predict the quasistatic broadening by iodine. [Preview Abstract] |
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