Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session A3: Plasma Physics- Low Temperature and Space Plasma Physics |
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Chair: Umair Siddiqui, West Virginia University Room: Waterfront Hotel Salon C |
Saturday, October 24, 2015 10:30AM - 10:42AM |
A3.00001: Atomic Layer Etching of SiO2 and Other Materials Using Decoupled Plasma Process Sequences Gottlieb Oehrlein An approach that uses steady-state Ar plasma in conjunction with periodic injection of a defined number of C$_{\mathrm{4}}$F$_{\mathrm{8}}$ molecules and synchronized plasma-based Ar$^{\mathrm{+}}$ ion bombardment, Angstrom-level precision in etching of SiO$_{\mathrm{2}}$ is possible.$^{\mathrm{1}}$ The physical sputter rate of SiO$_{\mathrm{2}}$ vanishes for low energy Ar$^{\mathrm{+}}$ ion bombardment conditions giving a maximum ion energy of about 20eV. On the other hand, for an FC-coated SiO$_{\mathrm{2}}$ surface, chemical modifications of the SiO$_{\mathrm{2}}$ surface are induced by low energy ion bombardment and SiO$_{\mathrm{2}}$ etching is initiated. We will discuss the temporal variation of the chemically enhanced etch rate of SiO$_{\mathrm{2}}$ for Ar$^{\mathrm{+}}$ ion energies below 30 eV as a function of fluorocarbon surface coverage which enables controlled removal of {\AA}ngstrom-thick SiO$_{\mathrm{2}}$ layers per process cycle. We will also review results on the extension of this approach to etching of silicon and overview challenges connected with controlling low pressure plasma surface interactions for the achievement of atomic scale precision in etching materials for pattern transfer. $^{\mathrm{1}}$ D. Metzler, R. Bruce, S. Engelmann, E. A. Joseph, and G. S. Oehrlein, J Vac Sci Technol A \textbf{32}, 020603 (2014) * Based on collaborations with D. Metzler, C. Li, S. Engelmann, R. Bruce, E. Joseph, E. Godyak, and M. Kushner. We gratefully acknowledge funding from National Science Foundation (CBET-1134273) and US Department of Energy (DE-SC0001939). [Preview Abstract] |
Saturday, October 24, 2015 10:42AM - 10:54AM |
A3.00002: The mechanisms of electron acceleration during magnetic reconnection James Drake, Joel Dahlin, Marc Swisdak Magnetic reconnection is the dominant mechanism for dissipating magnetic energy in space and astrophysical systems and is an efficient driver of energetic particles. Models of flares with a single reconnection site fail to explain the large number of energetic electrons seen in flares. Reconnection in large systems spontaneously develops at multiple sites, producing large numbers of magnetic islands that dominate magnetic energy release. There are three basic mechanisms for particle energy gain in reconnecting systems: motion along parallel electric fields; and the magnetic curvature and gradient B drifts along perpendicular electric fields. The latter two produce the classical Fermi and betatron acceleration, respectively. In situ satellite observations in the magnetosphere suggest that Fermi reflection drives most ion heating. The observational evidence on electron heating is not as clear. Particle-in-cell simulations suggest Fermi reflection dominates the energy gain of the most energetic electrons. The production of energetic electrons in 3D simulations, where magnetic fields become stochastic, dramatically increases compared with 2D. An extension of the Parker transport model to describe reconnection-driven particle acceleration in macroscale systems has been developed. [Preview Abstract] |
(Author Not Attending)
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A3.00003: The Common-origin of Kinetic Turbulence and Electron-Halo of Velocity Distribution Function in the Solar Wind Haihong Che Observations of solar wind show that the power spectra of magnetic fluctuations break from Kolmogorov scaling law at ion inertial length. Moreover, the electron velocity distribution function of solar wind exhibits an isotropic halo. What causes the spectral break and electron halo are two puzzles in heliophysics. I present a new model (Che et al., PRL and ApJL 2014) that accounts for both puzzles---the kinetic turbulence and electron halo of solar wind originate from the nanoflare-accelerated keV electron beams in the inner corona. With PIC simulations, we found that the electron beams drive strong two-stream instabilities. The nonlinear evolution of the two-stream instability gives rise to an isotropic electron halo, kinetic Alfvenic wave and whistler wave turbulence through forward and inverse energy cascades.The most important predictions of this model include: 1) the energy injection plateau in the magnetic power spectra; 2) the enhanced parallel electrostatic fluctuation in the solar wind; 3) the core-halo relative drift, a relic of saturated two-stream instability; 4) the temperature ratio of core-halo is determined by the beam instability heating property. The generation of Langmuir waves can produce type III micro-radio bursts that resemble the well-studied type III bursts observed in solar flares. [Preview Abstract] |
Saturday, October 24, 2015 11:06AM - 11:18AM |
A3.00004: Designed and early testing results of a microscale plasma spectrometer, for use in swarming multi-spacecraft measurements Drew Elliott, Amy Keeseee, Earl Scime, Matt Dugas, Steve Ellison, Joe Tersteeg, Alexander Barrie, Craig Pollock, Amy Rager Advanced lithographic techniques are used to design and build a plasma spectrometer which requires lower voltages and has a much smaller volume than typical retarding field energy analyzers. The total volume of the completed device is slightly larger than 1 cm$^{3}$. The designed measurement range is 2-20 eV/e. 100 V will be the maximum voltage supply needed for the device which is 1-3 orders of magnitude below that of traditional top hat retarding field energy analyzers. The required power for the energy analyzer itself is designed to be in the microwatt range, making it 6-7 orders of magnitude below that of similar state of the art devices, although detector and signal processing power requirements will likely be on the order of milliwatts. Early results from electron beam tests on the collimator and the energy analyzer are presented, and both are shown to behave very similar to predictive values simulated through SIMION$^{TM}$. [Preview Abstract] |
Saturday, October 24, 2015 11:18AM - 11:54AM |
A3.00005: TBD Invited Speaker: Weichao Tu |
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