Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session KW4: Negative Ion and Dust-Particle-Containing Plasmas |
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Chair: Hyo-Chang Lee, Korean Institute for Standards and Science Room: Oregon Convention Center A107-A109 |
Wednesday, November 7, 2018 2:00PM - 2:15PM |
KW4.00001: Modeling the dynamics of nanoparticle charging in pulsed plasmas Uwe Kortshagen, Toshisato Ono Studies focusing on the influence of dust particles on a discharge afterglow are scarce. In general, after the power source is removed, the electron temperature decreases rapidly on a time scale of the energy relaxation time, typically on the scale of microseconds. The electron density is also expected to decrease rapidly via recombination and/or diffusion losses to the boundaries. However, if electron detachment from the particles is a significant process, it can contribute to electron generation in the afterglow. In this study, the evolution of the electron desorption and electron-ion recombination on particle surfaces during the afterglow was investigated through modeling. The electron binding energy to the charged particle surface and the electron desorption rate were evaluated using quantum mechanical calculations by Bronold et al. [Contrib. Plasm. Phys., 49, 4-5, 303-315 (2009)]. The model suggests that electron detachment from particles can lead to a momentary increase of the electron density in the afterglow of pulsed dusty plasmas. [Preview Abstract] |
Wednesday, November 7, 2018 2:15PM - 2:30PM |
KW4.00002: Dust particle dynamics in the afterglow of pulsed RF dusty plasmas Toshisato Ono, Yunxiang Qin, Zhili Zuo, Changgong Wang, Song-Moon Suh, Chris Hogan, Uwe Kortshagen The spatiotemporal evolution of dust particles in plasmas is of interest for applications in the particle synthesis in plasmas and the mitigation of contamination issues in semiconductor processing. In this work, particle visualization by laser light scattering (LLS) measurements has been conducted in dusty argon plasmas generated in an RF capacitive reactor. We particularly focus on the particle dynamics in the afterglow of a pulsed plasma. In this regime, the predominant forces acting on particles rapidly change from the electrostatic and ion drag forces to the neutral drag and thermophoretic forces. Particle size effects are of particular interest. We utilized a combination of an ultrasonic nebulizer and a drying column to deliver dry highly monodisperse particles into the reactor. The LLS results suggest that particle trapping locations in steady-state and settling velocity in the afterglow plasma strongly depend on particle size. [Preview Abstract] |
Wednesday, November 7, 2018 2:30PM - 2:45PM |
KW4.00003: Coagulation growth kinetics of nanoparticles in non-stationary plasma. Vladislav Vekselman, Mikhail Shneider, Yevgeny Raitses Coagulation growth kinetics of nanoparticles in plasma is affected by inter-particle electrostatic forces due to charging phenomenon. In stationary plasmas, flux of plasma electrons reaching nanoparticles usually dominates over other charge carriers and particles acquire the so-called floating potential. Unipolar charging of particles results in retardation of nanoparticles growth and may result in limitation on a particle size. In current work we demonstrate opposite effect that is an enhancement of the particles growth in atmospheric pressure non-stationary arc discharge. Modeling of the growth kinetics revealed the formation of bipolar charge distribution of nanoparticles. As a result, Coulomb forces reversal from repulsive to attractive between nanoparticles promotes enhanced growth rates. This mechanism may explain an experimental observation of the grow of large micron size particles in the carbon arc. [Preview Abstract] |
Wednesday, November 7, 2018 2:45PM - 3:00PM |
KW4.00004: A Study on the Plasma Condition for Design of Neutralizer with High Neutralization Efficiency Jang-Jae Lee, SiJun Kim, YoungSeon Lee, SeungWan Yoo, ChulHee Cho, ShinJae You Plasma neutralization is used for high-energy neutral beam injection into fusion plasma. It is necessary to optimize the plasma source used for the neutralizer in order to improve the neutralization efficiency. In this study, plasma condition for improving the neutralization efficiency of negative ion beam (H-) in hydrogen plasma were investigated. The plasma neutralization efficiency was calculated using differential equations of beam fraction. To calculate the differential equations, density of target species in plasma which are derived from a global model, and cross sections which are dependent on the relative speed between colliding particles, such as beam particle and electron, were used. The dependence of neutralization efficiency of negative ion beam in the hydrogen plasma on electron density, electron temperature, and pressure were investigated. [Preview Abstract] |
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