Bulletin of the American Physical Society
2007 APS Four Corners Section/SPS Zone 16 Joint Fall Meeting
Volume 52, Number 14
Friday–Saturday, October 19–20, 2007; Flagstaff, Arizona
Session E1: Poster Session |
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Chair: Gary Bowman, Northern Arizona University Room: Science Lab Facility (Bldg. 17) Lobby |
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E1.00001: Vortex formation during the creation of Bose-Einstein condensates Tyler Neely, Chad Weiler, David Scherer, Brian Anderson We experimentally study the growth of Bose-Einstein condensates in harmonic trapping potential and potentials shaped by light. We find that vortices naturally form in the condensates during the evaporative cooling process with the probability influenced by the trap geometry. In all cases angular momentum in not deliberately added to the system. We will discuss past and on-going experimental results. [Preview Abstract] |
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E1.00002: Error-correction in distributed computational networks using self-organized collective dynamics Brian Myers, David Peak Dynamical processes on networks often exhibit self-organized collective behavior in which the activities of large numbers of nodes spontaneously synchronize without the intervention of a central processing unit (CPU). Sometimes such a synchronized state can be interpreted as ``performing a useful task.'' For concreteness, suppose the nodes of the network can take on state values 0 or 1. Initially, the network has some heterogeneous distribution of states, in which the majority state is assumed to be ``correct'' and the minority state is an ``error.'' The task is to identify which state is in the majority and to change all of the minority states to the correct value---without the assistance of a CPU. We show how the nodes can be wired together in a locally-connected architecture to produce a spatio-temporal dynamical system whose attracting state is all 0s or all 1s, depending on which was initially in the majority. We discuss a specific application for such a network that could potentially be of use aboard spacecraft in hostile radiation environments. [Preview Abstract] |
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E1.00003: Using Fluctuation Microscopy to Detect The Medium Range Order in Disordered Materials D. Kumar, M. Treacy, I. McNulty, M. DeJonge, L. Fan, D. Paterson, M. Gibson In this poster we present some results from our X-ray and optical fluctuation microscopy studies of disordered materials. Fluctuation microscopy is sensitive to any medium range order present in amorphous and disordered materials, and obtains this sensitivity by examining the spatial fluctuations in coherent diffraction scattering. The method derives this sensitivity because the normalized variance depends on pair-pair correlation functions and hence can be used to detect the subtle structural correlations. We are exploring two variations of the fluctuation microscopy idea. One promising approach, for varying the resolution function within the same scan, is to use an elliptical (or rectangular) probe-forming aperture. The idea is that diffraction data along the narrow slit direction corresponds to low-resolution ($i.e.$ large sample volumes), whereas diffraction data along the wide slit direction corresponds to high-resolution data ($i.e.$ small sample volumes). The (admittedly simplistic) idea is that all sampling resolutions between these two extrema can be found by tracing the diffraction data along the azimuthal angle corresponding to the desired aperture width. This approach may eliminate the need for taking a series of scans at different probe. [Preview Abstract] |
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E1.00004: Computer Modeling of Solar Ion Radiation Processing of Planetary Surface Materials Sydney Chamberlin, Roy Christoffersen Airless bodies in the interstellar environment are constantly bombarded with ions from stellar winds. Resulting ion-atom interactions gradually cause chemical and structural changes to occur on their surfaces. One of the more significant changes is the formation of amorphous rims on regolith grains. Ion transport physics gives some description of the dynamics underlying such radiation damage, but gives little insight into other factors such as the width of the damaged layer and the degree of amorphization over time. Monte Carlo simulation programs for modeling ion-atom interactions exist, but have never been fully exploited for use in space radiation processing and fail to accommodate the range of parameters present in plasmas such as the solar wind. In this study we have utilized an existing Monte Carlo program, Transport and Range of Ions in Matter (TRIM), to model radiation in the space environment. A series of input data files and calculation protocols were created to investigate a range of typical solar wind parameters. The new outputs of the model consist of damage profiles for the amount of deposited ion collision energy as a function of ion angle, solar wind energy distribution, and sputtering rate. Results obtained with this model are found to be in reasonable agreement with experimental measured results from irradiated mineral grains. [Preview Abstract] |
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E1.00005: Explorations in conformal symmetry for quantum relativity Lucas Earl, Jean-Francois Van Huele The conformal group is a supergroup of the Poincare group that leaves Maxwell's equations invariant. Conformal symmetry has many applications in physics. Can conformal symmetry be applied to bring together special relativity, which treats space and time on the same level, and quantum theory, which does not? Quantum relativity, as developed by Jaekel and Reynaud [1], introduces operators X$^{\mu}$ for space-time localization from the generators of the conformal group in an Einsteinian operational way. We explore how this approach can help describe elementary space-time processes like pair creation and pair annihilation. [1] M.T. Jaekel and S. Reynaud, Found.Phys.\textbf{28}, 439-456 (1998). [Preview Abstract] |
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E1.00006: Cerenkov Water-based Anti-neutrino Detection William Farmer A group of researchers at Lawrence Livermore National Laboratory have designed and constructed a water-based anti-neutrino detector to be used in monitoring plutonium content of reactor cores. This detector has the advantages over previous detectors in that it has a reduced foot print near the reactor core and it will be neither toxic nor flammable as previous detectors have been. In order to reduce backgrounds, a muon-veto was constructed to increase the signal to noise ratio. In this experiment, the researcher characterized the Photo-multiplier tubes to be used in the muon-veto and the central detector. From these results, researchers are confident that the new detector will be able to resolve the anti-neutrino signal. The detector is currently deployed at San Onofre Nuclear Generating Station and is collecting data. [Preview Abstract] |
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E1.00007: Structure and stability of a dipolar condensate with a singly quantized vortex Ryan Wilson, John Bohn, Shai Ronen In this work, we investigate the structure and stability of singly quantized vortices in Bose-Einstein condensates with long-range dipolar interactions. Using an efficient numerical algorithm based on Hankel transforms, we solve the Gross-Pitaevskii equation by minimization of the GP Energy functional and compute the excitation spectrum by solving the Bogoliubov-De Gennes (BdG) equations. The BdG modes define a stability region for the dipolar condensates and reveal the nature of their instability. We find that condensates with singly quantized vortices in pancake traps with polarization along the trap axis become unstable due to an angular roton. The number of radial and angular nodes in this roton is found to be proportional to the condensate size. Additionally, we confirm the presence of radial ripples on the ground state structures of these condensates and indicate a well defined region in which they are stable. [Preview Abstract] |
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E1.00008: Searching for Unresolved Binary Brown Dwarfs Jacob Albretsen, Denise Stephens There are currently L and T brown dwarfs (BDs) with errors in their classification of +/- 1 to 2 spectra types. Metallicity and gravitational differences have accounted for some of these discrepancies, and recent studies have shown unresolved binary BDs may offer some explanation as well. However limitations in technology and resources often make it difficult to clearly resolve an object that may be binary in nature. Stephens and Noll (2006) identified statistically strong binary source candidates from Hubble Space Telescope (HST) images of Trans-Neptunian Objects (TNOs) that were apparently unresolved using model point-spread functions for single and binary sources. The HST archive contains numerous observations of BDs using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) that have never been rigorously analyzed for binary properties. Using methods developed by Stephens and Noll (2006), BD observations from the HST data archive are being analyzed for possible unresolved binaries. Preliminary results will be presented. This technique will identify potential candidates for future observations to determine orbital information. [Preview Abstract] |
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E1.00009: Purity Measurements in Liquid Xenon Julio Cesar Benitez Medina, Kendy Hall, William Fairbank Detection of fluorescence from single Ba$^{+}$ daughter ions in liquid xenon is a potential key method of background discrimination in the Enriched Xenon Observatory (EXO) double beta decay experiment. An important requirement is to have ultrapure liquid in order to ensure Ba$^{+}$ ion survival for many seconds. To measure the purity of liquid Xenon we produce photoelectrons using a 355 nm Nd-YAG pulsed laser. As the electrons travel in the liquid some may be lost by attachment to impurities. By measuring the fraction of photoelectrons that survive, we can determine the purity of the liquid. The purity of the liquid is monitored before and after Ba$^{+}$ ions are deposited in the liquid by laser ablation. In some cases, ablation causes a purity decrease, but in other cases, it does not. We are gaining an understanding of what conditions allow Ba$^{+}$ ion deposition without purity degredation. [Preview Abstract] |
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E1.00010: Type Ia Supernovae: Standard Candles Used to Calculate Galactic Distance Joanna Gordon The light curve of a type Ia supernova is used to produce an estimate of the host galaxy's distance. Type Ia supernovae are good candidates to be used as standard candles. Because of the physical processes by which they are created, type Ia supernovae emit a standard, known luminosity during their peak energy output. By employing the difference between the supernova's apparent magnitude and its known, absolute magnitude, the distance of the explosion, and hence the distance of the host galaxy, is calculated. A light curve is constructed for a specific supernova by collecting a group of data over the period of several weeks and determining the apparent magnitude for the supernova corresponding to each data point. Each data point represents one night of observation. The distance of the selected type 1a supernova is then calculated. [Preview Abstract] |
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E1.00011: Resistivity of Kapton E at Intermediate Time Scales Following High-Energy Electron Irradiation Steven Hart, J.R. Dennison, Jeri Brunson, Jodie Gillespie Kapton E, a highly-insulating polymer, exhibits a characteristic DC resistivity. The resistivity of Kapton E is altered due to the effects of high energy electron irradiation. Measurements of resistivity were made several days following the electron bombardment. These values are discussed in terms of hopping conductivity theory and traps with intermediate-scale lifetimes. Additional anomalous behavior is also considered. [Preview Abstract] |
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E1.00012: A Versatile Hollow Cathode Discharge Tube for Si Spectroscopy Adam H. Marshall, William M. Fairbank, Jr., Siu Au Lee A simple stainless steel hollow cathode discharge tube has been constructed and utilized for the generation of silicon atoms, allowing for observation of Si spectra down to the deep UV range. The cathode plates may be easily replaced, allowing the user freedom to choose many different atomic sources. The discharge may be utilized for Doppler-free saturated-absorption spectroscopy and optogalvanic spectroscopy in the deep UV, to determine the hyperfine structure of Si29. This will be important for the laser cooling and trapping of Si, which is the first step towards making a Si quantum computer. [Preview Abstract] |
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E1.00013: A planet orbiting inside of a star. Alexander Panin Most of stars pass via the state of red giant during their evolution partially engulfing their planetary systems. We investigate theoretically and computationally how a planet moves inside of such star and how quickly it heats up. Surprisingly, our modeling shows that a planet does not quickly disintegrate inside of a red giant star nor does it even change its orbit quickly -- in some cases a planet continues to orbit below a photosphere of a red giant star for thousands of years, and in some other cases - for millions of years (!). [Preview Abstract] |
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E1.00014: Complex conductivity studies in UTX compounds Sourav Adak, Karunakar Kothapalli, Abdel Alsmadi, Heinz Nakotte, Ross McDonald, Ekkehard Bruck We have performed RF skin depth measurements of selected uranium compounds in applied magnetic fields up to 50 T. This technique is relatively new, as applied to metallic samples but is a useful probe of magnetotransport since the skin depth can be simply related to the magnetoresistance. [Preview Abstract] |
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E1.00015: Photocurrent Measurements on Novel Group IV Semiconductor Alloys Jay Mathews, Radek Roucka, Shui-Qing Yu, John Tolle, John Kouvetakis, Jose Menendez A system was developed for measuring photocurrent as a function of incident power and wavelength in new Ge$_{1-y}$Sn$_{y}$ semiconductor alloys. Detectors based on this material are expected to operate at wavelengths longer than possible in Ge-detectors due to the lowering of the band gap induced by Sn. Photocurrent measurements were taken on several alloys with incident light at 1.55 $\mu$m for a large range of intensities. Additionally, the absorption coefficient of these samples was determined as a function of wavelength. [Preview Abstract] |
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E1.00016: A rapid, objective method for detection of non-uniform steps in noisy signals. Bennett Kalafut, Koen Visscher Biophysical techniques, such as single molecule FRET, fluorescence microscopy, single ion-channel patch clamping, and optical tweezers often yield data that are noisy time series containing discrete steps. Here we present a method, based on the Schwarz Information Criterion, enabling objective identification of nonuniform steps present in such noisy data. Our method requires no assumption of underlying kinetic or state models and is hence particularly useful in the analysis of novel or poorly understood systems. [Preview Abstract] |
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E1.00017: Quantum Mechanics as Biconformal Measurement Thomas Williams, James Wheeler Biconformal space has been shown to contain all necessary properties of quantum Mechanics. Using three postulates to define motion and measurement in biconformal space, the standard formulation of quantum mechanics has been derived. Using any of a certain class of complex representations of the conformal group, it has been shown that quantum probabilities naturally arise from the use of a standard of measurement on biconformal space. We investigate the nature of this class of representations in detail to determine what, if anything, makes them the preferred way to think of quantum mechanics on biconformal space. [Preview Abstract] |
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E1.00018: High Altitude Experiments Shane Mayer-Gawlik, Joanna Gordon Carried by a weather balloon to 95,000 ft and back, our instruments recorded temperature, pressure, and acceleration. The acceleration data was collected to demonstrate the deviation from 9.8 m/s2 in Earth's gravity at high altitude. The change in acceleration due to gravity is expected to be about 0.02 m/s2. The Equivalence Principle of general relativity presents a challenge in measuring this quantity. There is no way to tell whether the accelerometer is measuring change in velocity or a gravitational field. Temperature and barometric pressure data were collected in order to study the thermodynamic properties of air. In addition, we calculated sound speed as a function of altitude based on this thermodynamic data, under the assumption of ideal gas behavior. [Preview Abstract] |
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E1.00019: Yb-doped chirped pulse amplification system Federico Furch, Brendan Reagan, Bradley Luther, Jorge Rocca A very compact, all diode pumped chirped pulse amplification system was developed based on Yb-doped gain materials. A passively mode-locked Yb:KYW oscillator in combination with a photonic crystal fiber was used to seed two different regenerative amplifiers. Energies up to 10mJ at 20Hz were obtained for cryo-cooled Yb:YLF and 6.5mJ between 10Hz and 30Hz for Yb:YAG at cryogenic temperatures also. For Yb:YAG it was possible to blue shift the spectrum of the oscillator to match the wavelength of the amplifier and the seed beam without using the non-linear fiber. The entire system (oscillator-stretcher-amplifier) has a footprint of less than 2m$^{2}$. After compression it should be possible to obtain amplified pulse duration of $<$8ps. [Preview Abstract] |
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E1.00020: Size Determination of Nanoscopic Droplet Beams by Transverse Impact of a Supersonic Free-Jet Expansion. R.K. Juday, R.B. Doak Droplet beams are developing into important tools for injection of hydrated macromolecules into vacuum for examination by x-ray and electron beams. Smaller is better in this pursuit and droplets are approaching nanoscale size, for which characterization by optical microscopy is precluded. Mie scattering offers size determination down to about $\lambda $/2, but is not trivial. New techniques for droplet size measurement are therefore of interest. We propose herein a method based on passing the droplet beam in vacuum through a gaseous free-jet expansion oriented transversely to the droplet beam. Directed impact of the gas against the droplets supplies transverse momentum, deflecting the droplets in a manner similar to the molecule-molecule scattering scheme of Buck, et al. [Phys. Rev. Lett. \textbf{52}, 109 (9184)] but with much larger total momentum transfer and in a quasi-continuum scattering regime that removes the ambiguities of molecule-molecule scattering dynamics. The deflection depends on the size of the droplet and so offers a means of determining droplet size and/or sorting droplets according to size and/or steering a droplet beam. This work presents an initial feasibility study to estimate the droplet deflection that is possible with existing supersonic free-jet expansions. The results indicate that this technique is eminently viable. [Preview Abstract] |
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E1.00021: Laboratory Nuclear Astrophysics Research, the Universe Viewed from Underground Samuel Olson The field of Laboratory Nuclear Astrophysics, in the words of Rolfs, ``{\ldots} is often a frustrating science. The desired cross sections are among the smallest measured{\ldots} often requiring long data collection times with painstaking attention to background. {\ldots}from a purely nuclear point of view, the reactions studied are often of comparatively little interest.~{\ldots} [It] requires specialized equipment and environments.'' In our efforts to study nuclear astrophysics, we have realized the truth of all of these statements. In the past, nuclear astrophysics was studied by accelerating high energy ions into gas targets, using beam energies ranging down to about 10 keV. Below this energy, reaction rates are so low that they are nearly impossible to detect. We report here our efforts to study fusion rates from low-energy reactants. [Preview Abstract] |
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E1.00022: Investigating the Photoyield of Spacecraft Materials Jennifer Albretsen, Ryan Hoffmann, John R. Dennison Understanding the photon-induced charging of spacecraft materials is necessary in modeling the overall charging of a spacecraft. Measuring the photoyields of insulators requires sophistication, since insulators' electrons must overcome a greater potential energy barrier, than electrons in a metal, to move within a solid. In order to determine the photoyields of insulating and semiconducting materials for NASA's Solar Probe Mission (PBN, Alumina) and James Webb Space Telescope project (SixPI-ExVDA), a chopper and lock-in amplifier were added to a photoyield measurement system. A standard (Au) photoemission spectrum was compared with Au spectrum taken before addition of the lock-in to verify the validity of the modified system. Two insulators (polyboron nitride and Alumina) under investigation for the NASA/APL Solar Probe Mission and materials for the JWST project (vapor deposited aluminum and silicon on substrate Kapton E) were then studied using the modified photoemission measurement system. The resulting spectra were used to calculate the solar photoelectron yield and work function of each of the materials. [Preview Abstract] |
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