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 HW2: Dusty Plasmas and Negative Ions |
Hide Abstracts |
Chair: Masaru Shiratani, Kyushu University Room: State C |
Wednesday, November 5, 2014 8:00AM - 8:15AM |
HW2.00001: Coulomb Crystals in Cylindrical Dusty Plasmas under Gravity/Microgravity Kazuo Takahashi, Hiroo Totsuji, Satoshi Adachi Coulomb crystals of dusty plasmas have been studied under microgravity with utilities boarding on the International Space Station in a joint Russian/German research project. Dynamics of the Coulomb crystals in cylindrical plasmas is investigated with the apparatus of PK-4 being launched till the end of 2014. A science team in Japan studied the cylindrical dusty plasmas to contribute to the project with the PK-4J modified original for microgravity experiments of parabolic flights in Japan. In the experiments, the dust particles distributed at the off-centered position close to the bottom in balancing of gravity. Under microgravity, they changed the distribution and formed a Coulomb crystal around the center axis in the plasmas. Several particles arranged in a line parallel to the axis, and the lines piled up to a bundle.\footnote{K. Takahashi, M. Tonouchi, S. Adachi and H. Totsuji, Int. J. Microgravity Sci. Appl. {\bf 31}, 62 (2014) 62.} Spatial distribution of the dust particles affects on plasma parameters of ion density and electron temperature. Structures of the Coulomb crystals connected to the parameters are discussed. [Preview Abstract] |
Wednesday, November 5, 2014 8:15AM - 8:30AM |
HW2.00002: Langmuir probe measurements of the electron energy probability function and laser scattering in nanodusty plasmas Narula Bilik, Yunxiang Qin, Eray Aydil, Uwe Kortshagen A Langmuir probe was used to measure real-time electron energy probability distribution function (EEPF) in argon-silane dusty plasma generated by a RF capacitive reactor. The challenge of Langmuir probe measurements in dusty plasma is the coating of the probe surface: A dielectric layer formed by dust particles causes a series resistance and changes the probe work function, leading to inaccuracy in EEPF measurements. We addressed this problem by adding an actuated ceramic shield to the probe. With the actuated shield the probe was exposed to the dusty plasma only when it was measuring and under rapid I-V scan, minimizing the exposure and effectively preventing coating. EEPFs in dusty plasma were captured in 80mtorr and 40W dusty plasma (10sccm argon and 4.7sccm 5\% silane in argon flow). Simultaneous measurements of the ion density with a capacitive probe and real-time laser scattering was performed to further characterize the plasma. As particles form in dusty plasma, the electron density dropped but electron temperature increased. The electron density in the dusty plasma dropped much more compared to the ion density due to the attachment of electrons to the growing particles. [Preview Abstract] |
Wednesday, November 5, 2014 8:30AM - 8:45AM |
HW2.00003: Correlation between nanoparticles formation and plasma parameters evolution in magnetically confined C$_{2}$H$_{2}$/Ar plasma Georges Al Makdessi, Joelle Margot, Richard Clergereaux Dusty plasmas are plasmas containing charged nano-sized or even charged micro-sized particles. Known for decades, dusty plasmas have attracted the interest of the scientific community in the early 80s, especially in astrophysics when dusty particles were discovered in the rings of Saturn [1]. Comets and planetary rings are some examples of natural objects formed by dusty plasmas [2]. Dusty particles are also found in laboratories plasmas such as those used for deposition and etching of thin films. In this presentation, we investigate magnetically confined low pressure dusty plasmas in acetylene. The plasma is created by an electromagnetic surface wave at a frequency of 200 MHz. By performing a parametric study of the influence of the magnetic field on the formation of dust particles and on the plasma properties, we expect to achieve a good understanding of their creation mechanisms, and, ultimately to control their characteristics. \\[4pt] [1] B.A. Smith et al. Science 215 (4532), 504 (1982) \newline [2] C.K. Goeretz, Rev. Geophys. 27, 271 (1989) [Preview Abstract] |
Wednesday, November 5, 2014 8:45AM - 9:00AM |
HW2.00004: Nanoparticle heating at atmospheric pressures Nicolaas Kramer, Eray Aydil, Uwe Kortshagen Plasma growth and crystallization of nanoparticles is an exciting new frontier both for plasma science as well as materials research. To date, the mechanisms of nanoparticle charging and heating in nonthermal plasmas have been studied and understood to some extent for low pressure plasmas. However, particle charging and heating at atmospheric pressures have been little explored. The fundamental processes of nanoparticle charging and heating are significantly different at atmospheric pressure compared to low pressures. Charging is determined through collision enhanced or hydrodynamic, mobility driven collection of ions by the nanoparticles rather than by orbital motion at low pressures. Nanoparticle heating reactions have to compete with nanoparticle cooling through convection/conduction to the neutral gas that is about 100-1000 times faster than at low pressure. Here, we present a Monte Carlo model that stochastically treats nanoparticle heating reactions such as electron-ion recombination and energetic surface reactions. Nanoparticle cooling through conduction/convection is modeled through a continuum model. The model indicates at atmospheric pressure, the nanoparticle temperature on average remains much closer to the gas temperature than at low pressure. [Preview Abstract] |
Wednesday, November 5, 2014 9:00AM - 9:15AM |
HW2.00005: Numerical Modeling of a Pulsed Argon-Silane RF Plasma with Biased Substrate for High-Velocity Deposition of Nanoparticles Steven Girshick, Carlos Larriba-Andaluz It has been hypothesized that deposition of very small silicon nanoparticles during plasma-enhanced chemical vapor deposition of silicon, under conditions where the particle impact velocity is high enough to cause particle melting/amorphization, can lead to epitaxial film growth at low temperature [1]. One way to accomplish this might be by pulsing the RF plasma and applying a positive DC bias during the afterglow of each pulse. The negatively charged particles, trapped in the plasma during the ON phase of each pulse, are accelerated to the substrate during the afterglow. To assess the feasibility of such an approach, we conducted numerical simulations of a pulsed capacitively-coupled RF Ar-silane plasma. We used a modified version of a previously reported 1D model, in which a nanodusty plasma is simulated by self-consistently coupling models for the plasma, chemistry and aerosol [2]. Preliminary results indicate that the approach is feasible, but that parameters such as pulse frequency and duty cycle are important in limiting particle growth and in maximizing fluxes of energetic nanoparticles to the substrate. [1] P. Roca i Cabarrocas, R. Cariou and M. Labrune, J. Non-Cryst. Sol., 358, 2000 (2012). [2] P. Agarwal and S. L. Girshick, Plasma Chem. Plasma Process. 34, 489 (2014). [Preview Abstract] |
Wednesday, November 5, 2014 9:15AM - 9:30AM |
HW2.00006: Hydrogen negative-ion surface production on diamond materials in low-pressure H2 plasmas Gilles Cartry, Kostiantyn Achkasov, C\'edric Pardanaud, Jean-Marc Layet, Alain Simonin, Alix Gicquel Negative-ion sources producing H- current density of $\sim$ 200 A/m2 are required for the heating of the fusion plasma of the international project ITER. The only up-to-date solution to reach such a high H- negative-ion current is the use of cesium (Cs). Deposition of Cs on the negative-ion source walls lowers the material work function and allows for high electron-capture efficiency by incident particles and thus, high negative ion yields. However, severe drawbacks to the use of Cs have been identified and its elimination from the fusion negative-ion sources would be highly valuable. Volume production is not efficient enough at low-pressure to reach the high current required. Therefore, we are working on alternative solutions to produce high yield of H- negative-ions on surfaces in Cs-free H2 plasmas. In this communication, we will detail the methodology employed to study negative-ion surface production. In particular we will describe how the negative-ions are extracted from the plasma, and how we can obtain information on surface production mechanisms from the measurement of the H- energy distribution functions. We will present some results obtained on diamond surfaces and show that diamond is a promising candidate as a negative-ion enhancer material in low-pressure H2 plasmas. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700