Bulletin of the American Physical Society
2008 Joint Fall Meeting of the Texas and Four Corners Sections of APS, AAPT, and Zones 13 and 16 of SPS, and the Societies of Hispanic & Black Physicists
Volume 53, Number 11
Friday–Saturday, October 17–18, 2008; El Paso, Texas
Session J4: Plasmas, General Relativity, and Cosmology |
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Chair: Eric Hagedorn, The University of Texas at El Paso Room: Union East, 3rd Floor Smiley |
Saturday, October 18, 2008 1:30PM - 1:42PM |
J4.00001: Modeling the FTICR-MS signal of a $^7$Be ion plasma using a 2D PIC code M. Takeshi Nakata, Grant W. Hart, Bryan G. Peterson, Ross L. Spencer Beryllium-7 ($^7$Be) only decays by electron capture into lithium-7 ($^7$Li) with a half life of 53 days. As a result, its decay rate depends on the electron density around its nucleus. We desire to study the effect of ionization on its decay rate. We will do this by trapping a $^7$Be ion plasma in a Malmberg-Penning Trap and measuring its and $^7$Li's concentration as a function of time by using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). We use this ratio as a function of time to directly measure the decay rate of the confined ion plasma rather than using gamma detection. We have modeled these signals in a 2-dimensional electrostatic particle-in-cell (PIC) code. The two spectrum peaks merge at high densities and at low densities they can be resolved. The merged peak linearly shifts with the relative abundances of the species. We have also modeled $^7$BeH$^+$ and $^7$Li$^+$ at high densities. These two spectrum peaks shift with the relative abundances of the two species. The progress of this investigation will be presented. [Preview Abstract] |
Saturday, October 18, 2008 1:42PM - 1:54PM |
J4.00002: A New Design and Model for Plasma Spraying with an Inductively Coupled RF Plasma Torch Eddie Holik III, Peter McIntyre, Akhdiyor Sattarov Plasma torches are commonly used to coat metal substrates with a refractory outer cap material. This is accomplished by introducing the coating as a powder into the plasma plume as it exits the torch or on the central axis with a carrier gas. These locations are effective at heating the powder but offer little control over powder temperature. This work proposes to take advantage of some of the properties of an inductively coupled RF plasma torch (ICPT) to introduce the powder spray as an aerosol dispersion in an inert carrier gas directly into certain flow streamlines as they enter the plasma torch. Moreover, multiple powders may be introduced onto different streamlines, which are then heated to different temperatures in the torch, to provide control of non-equilibrium-phase reactions. Modeling the fluid dynamics and temperature distribution is critical in designing such a plasma torch. Computer simulation of current and potential ICPT designs and some prospective uses will be presented. [Preview Abstract] |
Saturday, October 18, 2008 1:54PM - 2:06PM |
J4.00003: ICF Hohlraum Energy Loss Through Diagnostic Holes and Apertures T.E. Tierney, R.G. Watt, H.E. Tierney, R.J. Kanzleiter, G.C. Idzorek, R.R. Peterson, M.R. Lopez, M.C. Jones The Z dynamic hohlraum (DH) was used to examine inertial confinement fusion energetics and radiation transport. A 2.4-mm diameter, 4-mm high copper-walled hohlraum is mounted above the DH to capture $\sim $100 kJ of axially-emitted quasi-Planckian radiation (T$_{rad} \quad \sim $ 180-220 eV). A 1-mm diameter hole was placed at the top of the hohlraum, while some targets had an additional 400-micron wide groove cut in the side. A 4-mm diameter cylinder of 60 mg/cc silica aerogel foam surrounds the hohlraum to produce blast waves (BWs) out the top and sides of the hohlraum. The propagated distance and shape of the BWs provides estimates of time-integrated energy delivered to the foam. Single frame soft x-ray imaging recorded the formation of BWs as well as wall ablation and motion.~ This experiment diagnosed energy loss through apertures in hohlraums by use of BW measurements. We discuss the experiment results in comparison to 2-D radiation hydrodynamic simulations. [Preview Abstract] |
Saturday, October 18, 2008 2:06PM - 2:18PM |
J4.00004: Computational Analysis of the Decay Constant of $^{7}$Be$^{+}$ and $^{7}$BeH$^{+}$ Mark Hutchison, Bryan Peterson $^{7}$Be is the lightest element that decays solely by electron capture. $^{7}$Be is therefore a prime candidate for exploring the nature of electron capture. Despite the long history of research done on $^{7}$Be, there is no accepted value for its half-life. All other measurements of the half-life of $^{7}$Be have been performed by inserting it interstitially into other elements. By confining singly ionized $^{7}$Be atoms in a non-neutral plasma, we can obtain a measurement for its decay constant with a known fraction of 2s electrons. Since we will not need to worry about approximations due to interactions with other elements, our measurement may be important in confirming the work done by P. Das and A. Ray [1]. I will be presenting about our current efforts in calculating a predictive value for the change in the decay constant for singly ionized $^{7}$Be by calculating the electron charge density near the nucleus. I will also present how we can use the wave functions for Hydrogenic ions as an important check for our calculations and show some of our preliminary findings. [1] Das, P., and Ray, A., ``Terrestrial $^{7}$Be decay rate and $^{8}$B solar neutrino flux,'' Phys. Rev. C \textbf{71}, 025801 (2005). [Preview Abstract] |
Saturday, October 18, 2008 2:18PM - 2:30PM |
J4.00005: Chaos in General Relativity: Spinning Particles around Black Holes Chris Verhaaren We consider the possibility of chaotic particle orbits in General Relativity. We discuss some of the difficulties in quantifying chaos in General Relativity. In particular, we solve the Papapetrou equations for spinning particles in the background of a black hole and compare our results with the non-spinning case. [Preview Abstract] |
Saturday, October 18, 2008 2:30PM - 2:42PM |
J4.00006: Constraint conserving boundary conditions in general relativistic magnetohydrodynamics Michael Besselman Astrophysically, we observe many compact objects, such as neutron stars, which in addition to being examples of strong field gravity, also carry a magnetic field. We are interested in simulating the evolution of such objects using general relativistic magnetohydrodynamics (GRMHD). An important aspect in these models is ensuring that physical constraints are everywhere satisfied during these computations. We describe our efforts to impose consistent boundary conditions to maintain the vanishing of the divergence of the magnetic field. [Preview Abstract] |
Saturday, October 18, 2008 2:42PM - 2:54PM |
J4.00007: The Contribution of The Cosmological Constant/Dark Energy to The Bending of Light and its Applications. Mustapha Ishak, Wolfgang Rindler, Jason Dossett, Jacob Moldenhauer, Chris Allison We report new results on the effect of the cosmological constant Lambda on the bending of light by a spherically symmetric mass. We show that when the Schwarzschild-de Sitter geometry is taken into account, Lambda does indeed contribute to the bending of light. We use this result to discuss an amended lens equation and new time delay expressions. Although the newly derived Lambda-terms are perhaps small for current observations, they do not cancel out. We apply the result to observations of Einstein radii around several systems where the lens is a cluster of galaxies. We find that the contribution of the Lambda-term to the bending angle can be as large as the second-order term in the Einstein deflection angle for many lens systems and even larger in some cases. We show that our results derive from various methods including the exact matching of solutions to Einstein's equations, approximations used in gravitational lensing, and Fermat's Principle. [Preview Abstract] |
Saturday, October 18, 2008 2:54PM - 3:06PM |
J4.00008: Magnetized Stars in General Relativity Eric Hirschmann, Jared Greenwald While magnetic fields are ubiquitous features of stellar systems, it is only relatively recently that the evolution of compact objects such as neutron stars have been simulated using both general relativity and ideal magnetohydrodynamics. An important aspect of these simulations is beginning with physically reasonable initial data. To this end, we consider the problem of constructing equilibrium configurations of axisymmetric, polytropic stars with strong magnetic fields in general relativity. [Preview Abstract] |
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