Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 62, Number 17
Friday–Saturday, October 20–21, 2017; Fort Collins, CO
Session C7: Plasma Physics I: Low Density and Cold Plasmas |
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Chair: Mark Siemans, University of Denver Room: Lory Student Center 386 |
Friday, October 20, 2017 10:30AM - 10:42AM |
C7.00001: A 4D Model of the Io Plasma Torus using Diffusive Equilibrium Parker Hinton, Fran Bagenal, Kaleb Bodisch Jupiter's moon Io volcanically outgasses roughly 1000kg/s of neutral atoms that, through various physical mechanisms, end up as plasma in Jupiter's magnetosphere. This plasma then becomes distributed along magnetic field lines according to diffusive equilibrium and assumes an overall toroidal structure with a few distinct sections. These sections include the cold inner torus (disk), a portion between the disk and the orbit of Io (duct or sometimes called the ribbon), and the remaining warmer outer torus (donut). The disk exists from approximately 4-5.6 RJ, the duct exists from 5.6-6 RJ, and the donut portion extends from 6-10 RJ, where RJ is the radius of Jupiter (1 RJ $=$ 71,492 km). We seek to reproduce these three features in our 4D model, adding time (duration) as the last dimension. Current modeling efforts involve using a simple tilted dipole magnetic field model. This simple model effectively reproduces the bulk of the toroid -- the warmer outer donut. We experiment with other magnetic field models such as VIP4 in order to best match observations and improve the accuracy of our model. We further apply techniques of physical chemistry and ground based observations to develop understanding of the cold inner torus and to aid our modeling efforts. Our model includes various parameters that can be adjusted in order to gain further insight into the plasma torus. Such parameters include ion and electron temperatures, densities, and distributions, as well as the magnetic field model. [Preview Abstract] |
Friday, October 20, 2017 10:42AM - 10:54AM |
C7.00002: Finite element modeling of electrostatic discharge using a collisional plasma spark conductivity model John Rose, Mark Coffey, Philip Flammer, Michael LaCount, Liam Pocher, Claudia Schrama, Dan Borovina, Jonathan Mace, Charles Durfee Electrostatic discharge (ESD) is an important safety concern for many industrial operations, in particular those that involve risk for fire or explosion. A key aim for our work is to develop a physical model that can place limits on the current and energy of an ESD pulse that can be used for safety measures. We consider ESD pulses from charged, insulating materials to low-resistance victim loads. After implementing the full set of Maxwell equations in potential form using a finite element solver (COMSOL Multiphysics), we developed a framework for calculating the collisional processes in the spark channel plasma. We find that the energy that can be transferred to a low-resistance victim load is strongly limited by the surface resistance of the charged object and by the spark resistance, which is in turn fundamentally tied to the ionization of the gas. We have also analyzed simpler nonlinear spark resistance models that result from the thermodynamic energy balance for a cylindrically-uniform spark channel. We compared these simpler spark models alongside our more general plasma model and established which ESD regimes are valid for the simpler models. [Preview Abstract] |
Friday, October 20, 2017 10:54AM - 11:06AM |
C7.00003: Rydberg atom formation rate versus the three-body recombination rate in ultracold plasmas John Guthrie, Wei-Ting Chen, Jacob Roberts One of the main limitations to the lowest achievable electron temperatures in ultracold plasmas is the formation of Rydberg atoms through three-body recombination collisions. Such recombination collisions are predicted to obey a well-known electron temperature ($T$) scaling of $T^{-\frac{9}{2}}$ in plasmas. Such a predicted scaling, however, is true only given a careful definition of what a recombination rate is versus the what the overall Rydberg atom formation rate is. We present such considerations that are relevant for low-density ultracold plasmas and compare theory predictions to experimental measurements. The $T^{-\frac{9}{2}}$ scaling is not observed, but this is in line with expectations. While we have good agreement between theory and experiment for what should be steady-state populations of Rydberg atoms in ultracold plasmas, the predicted dynamics at earlier times are not in agreement between theory and experiment. [Preview Abstract] |
Friday, October 20, 2017 11:06AM - 11:18AM |
C7.00004: Trajectory Measurements on the Colorado Dust Accelerator Using a Dual Dust Coordinate Sensor William Goode, Tobin Munsat The Dust Coordinate Sensor (DCS) is a dual detector instrument located on the beamline of the 3 MV hypervelocity Dust Accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado, Boulder. This instrument measures the three-dimensional trajectories of charged, hypervelocity (3-8 km/s), micron-sized dust particles while in flight by utilizing the image charge on grids of wire electrodes. The position measurements are matched by timestamp with separate measurements of charge and velocity for each launched dust particle. By measuring the trajectories, the points of impact coordinates on a target can be pinpointed to within a fraction of a millimeter. This new capability also provides opportunities for profiling the particle beam. [Preview Abstract] |
Friday, October 20, 2017 11:18AM - 11:30AM |
C7.00005: Optimizing design of a VASIMR at UVU using single particle trajectories Sam Otero, Phil Matheson Magnetoplasma thrusters are likely to increase in importance for interplanetary missions. Of particular interest is the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR). A group of undergraduate students at Utah Valley University has initiated an exploration of the VASIMR with the intent to eventually build a model device. To optimize the configuration of device components we have developed a computational model using ion cyclotron resonant heating (ICRH) of singly-ionized argon atoms to explore particular device configures. We assume that the behaviors of single-particle motions may give insight to the response of the general plasma, and the analysis of the resulting data allows for optimization of device configurations. We present the results of our preliminary investigations. [Preview Abstract] |
Friday, October 20, 2017 11:30AM - 11:42AM |
C7.00006: Ion Sheath Formation in an Inductively-Coupled Plasma Mass Spectrometer Joseph Chandler Between the skimmer cone and the mass analyzer of an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) lies an electrostatic ion lens. The lens uses a large negative potential to remove the electrons from the plasma and to collimate the ions of the weakly ionized plasma, forming a plasma sheath. By using Boltzmann electrons and collisionless ions to computationally model this interaction, we can calculate the electrostatic potential and ion density near the skimmer cone. Doing this calculation on a cylindrically symmetric grid gives a version of Poisson's equation which is a second order nonlinear differential equation that can be solved using SOR. In this plasma sheath calculation, no pre-sheath is required due to the supersonic velocities of the ions. By calculating the position of the plasma sheath based on different initial conditions we are developing an understanding of how and where this sheath forms. [Preview Abstract] |
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