Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session BT1: Collision Data For and From Plasma Applications |
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Chair: Natalia Babaeva, University of Michigan Room: Salon E |
Tuesday, October 14, 2008 8:00AM - 8:30AM |
BT1.00001: The role of atomic and molecular collision processes in plasmas - and vice versa Invited Speaker: A broad base of accurate data of atomic and molecular collision processes is essential for reliable modelling, simulation, and diagnostics of plasmas. This is particularly important for plasmas at elevated pressures close to atmosphere. This regime attracts rapidly growing attention due to both - promising innovative technological applications as well as new fundamental scientific phenomena. The collision dominated environment and decreasing dimensions down to microscale plasmas with extremely high surface to volume ratios significantly increase the demand for collisional deactivation and surface interaction processes. Cross sections for collisional deactivation can be determined from the effective lifetime of excited states. Direct excitation using short pulse laser systems are most reliable however limited by optical selection rules and available photon energies. Recently improved understanding of the dynamics of electron impact excitation in radio-frequency discharges allows alternative strategies using space and phase resolved optical emission spectroscopy measurements coupled with careful modelling of the population dynamics of excited states. This method based on electron impact excitation is not limited by optical selection rules and also provides access to high energetic electronic states which are not accessible with common laser systems. Data for surface interactions is inherently delicate since it strongly depends on surface properties such as coverage and temperature. Nevertheless, reliable data for recombination of radicals and metastable states, and coefficients for secondary electron emission are highly desirable for consistent modelling and simulation. An alternative approach is the active implementation of experimentally measured surface sensitive parameters such as atomic radical densities and excitation structures caused by secondary electrons. These experimentally accessible quantities can be used as fixed input parameters in improved self-consistent modelling. [Preview Abstract] |
Tuesday, October 14, 2008 8:30AM - 9:00AM |
BT1.00002: Electron collision calculations for atomic systems and the use of this data in fusion and astrophysics modelling codes Invited Speaker: A brief overview will be given of the main theoretical and experimental methods used to calculate/measure electron impact ionization cross sections for use in fusion and astrophysics spectral modeling. Care must be taken when processing these cross sections into Maxwellian rate coefficients. Examples will be given showing the importance of the near threshold part of the cross section. Comparisons will be shown between data from current databases and illustrations given of how this data is commonly used in spectral modeling codes. Electron impact excitation and recombination data will also be discussed and future data needs will be highlighted. [Preview Abstract] |
Tuesday, October 14, 2008 9:00AM - 9:15AM |
BT1.00003: Time-Resolved Electron Density Measurements of Laser Produced Plasmas using X-Band Microwave Interferometry K. Ellen Keister, Jeffrey L. Putney, Clark J. Wagner, J. Gary Eden Laser produced plasma channels form a unique and significant laboratory tool for exploring the kinetics of plasma formation and decay. Using a sub-picosecond 100 GW ultraviolet laser system and a microwave interferometer operating at 9.2 GHz, time-resolved measurements are made of the electron density of the plasma. By vacuum sealing part of the interferometer, measurements are made at pressures between 10$^ {-2}$ and 10$^{3}$ Torr, and in a variety of gases, including neon, argon, xenon, nitrogen, and oxygen. Rate constants and multiphoton ionization and excitation cross sections can be extracted from the electron density decay rates, using a simple gas kinetic model in neon. The calculated constants are consistent with existing results. [Preview Abstract] |
Tuesday, October 14, 2008 9:15AM - 9:30AM |
BT1.00004: Radiative Losses of Solar Coronal Plasmas James Colgan, Joe Abdallah, Manolo Sherrill, Matt Foster, Christopher Fontes, Uri Feldman A comprehensive set of calculations of the radiative losses of solar coronal plasmas is presented. The Los Alamos suite of atomic structure and collision codes is used to generate collisional data for fifteen coronal elements. These data are used in the Los Alamos plasma kinetics code ATOMIC to compute the radiative power loss as a function of electron temperature. We investigate the sensitivity of the loss curves to the quality of the atomic data, changes in the coronal elemental abundances, and compare our results with previous work. [Preview Abstract] |
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