Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session Y13: Applications of Nuclear Physics and Beams |
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Sponsoring Units: DNP DPB Chair: L. Waters, Los Alamos National Laboratory Room: Washington 6 |
Tuesday, February 16, 2010 1:30PM - 1:42PM |
Y13.00001: Progress in Nuclear Detection Richard Vojtech The Transformational and Applied Research Directorate (TAR) was established within the Department of Homeland Security's Domestic Nuclear Detection Office (DNDO) to conduct, support, coordinate, and encourage near- and long-term Research and Development (R{\&}D) programs for break-through technologies designed to dramatically improve capabilities to detect and report illicit trafficking of nuclear and radiological materials. These programs cover a wide range of technologies and high-level technical challenges associated with the DNDO mission and the Global Nuclear Detection Architecture (GNDA). They encompass a range of technology levels, ranging from feasibility and proof of concept studies to technology demonstrations of systems. Even though the focus is on high level challenges, the direction of some topic areas can change from year to year. This presentation will provide an overview of the TAR mission and discuss the current status of transformational R{\&}D efforts in three major program areas: Advanced Technology Demonstrations (ATD), Exploratory Research (ER) and Academic Research Initiative (ARI). [Preview Abstract] |
Tuesday, February 16, 2010 1:42PM - 1:54PM |
Y13.00002: Measurement of Proton-Induced Delayed Neutron Cross-Sections at 800 and 4000 MeV Randy Spaulding, Chris Morris, Steven Greene, Greg Canavan, Zhehui Wang, Mark Makela, Laurie Waters, Kiwhan Chung, Fesseha Mariam, Jeffrey Bacon, Matthew Murray, Fred Wysocki, Gary Hogan Energetic proton beams are being used to explore delayed neutron emissions from a variety of materials in support of national security goals. To accomplish these goals it is necessary to have a firm understanding of the time structure of delayed neutrons emitted from the daughter nuclei of spallation, fragmentation, and fission interactions in structural and shielding materials as well as fissionable isotopes. Results of experiments conducted at Los Alamos National Laboratory (LANL) at 800-MeV and Brookhaven National Laboratory (BNL) at 4-GeV are presented. [Preview Abstract] |
Tuesday, February 16, 2010 1:54PM - 2:06PM |
Y13.00003: Directionality of Skyshine Radiation Warnick Kernan, Kenneth Conlin, Richard Kouzes, Emily Mace, Edward Siciliano, Mitchell Woodring Skyshine reflection, or the scattering off of the air above a source, is frequently observed in situations where large sources are incompletely shielded, such as radiography sources in shielding pits that are open to the sky. Originally, concern about skyshine regarded limiting the dose from the source. However, even in situations where dose is minimal, the contribution of skyshine may interfere with sensitive measurement instruments operating near background limits, such as with border security applications. To help determine effective methods for shielding sensitive detection systems from skyshine interference, a series of measurements and model simulations have been conducted using a specially configured, portable collimated detector and an iridium-192 source. This paper will report these results, and also show their similarity when compared to other measurements using different sources. [Preview Abstract] |
Tuesday, February 16, 2010 2:06PM - 2:18PM |
Y13.00004: Active Proton Interrogation for Homeland Security Steven Greene, Christopher Morris, Gregory Canavan, Kiwhan Chung, Jay Elson, Gary Hogan, Mark Makela, Fesseha Mariam, Matthew Murray, Alexander Saunders, Randy Spaulding, Zhehui Wang, Laurie Waters, Frederick Wysocki Energetic proton beams may provide an attractive technology for active interrogation of nuclear threats because: they have large fission cross sections, long mean free paths and high penetration, and proton beams can be manipulated with magnetic optics. We have measured time-dependent cross sections for delayed neutrons and gamma rays using 800 MeV protons from the Los Alamos Neutron Science Center and 4 GeV protons from the Brookhaven Alternating Gradient Synchrotron for a set of bare and shielded targets. The results show significant signals from both unshielded and shielded nuclear materials. Results will be presented. [Preview Abstract] |
Tuesday, February 16, 2010 2:18PM - 2:30PM |
Y13.00005: Novel Neutron Focusing Optics Yelena Bagdasarova Neutron scattering methods are among the most important tools for studying the structure and dynamics of matter. However, a neutron analog of an optical microscope has not been built so far, mostly because weak interactions of neutrons with most materials preclude making effectiveneutron lenses. The purpose of my research is to investigate and demonstrate the effectiveness of a novel neutron optics that might make neutron microscopy practical. This optics is based on an existing x-ray optics design known as Wolter optics. Its design consists of two confocal mirrors (elliptical or parabolic mirror followed by a hyperbolic mirror) that reflect neutron beams at grazing incidence from one focus to the other. The advantage of Wolter optics is that its geometry satisfies the Abbe's sine condition almost exactly, resulting in near-perfect imaging of small, off-axis objects. Effectiveness of the mirrors is explored by simulating the mirror design in a standard neutron ray-tracing software package. The mirror simulation is used to conduct numerical experiments in order to evaluate performance as a function of the geometry and properties of the mirror and source. The simulated results are compared with tests of real Wolter-type neutron mirrors, conducted at the MIT Nuclear Reactor Laboratory. [Preview Abstract] |
Tuesday, February 16, 2010 2:30PM - 2:42PM |
Y13.00006: SURF III: A flexible Synchrotron Radiation Source for Radiometry and Research Uwe Arp, Charles Clark, Lu Deng, Nadir Faradzhev, Alex Farrell, Mitch Furst, Rashi Garg, Steven Grantham, Edward Hagley, Shannon Hill, Thomas Lucatorto, Ping-Shine Shaw, Charles Tarrio, Robert Vest The calculability of synchrotron radiation (SR) makes electron storage rings wonderful light sources for radiometry. The broadband nature of SR allows coverage of the whole spectral region from the x-ray to the far-infrared. Compact low-energy storage rings like the Synchrotron Ultraviolet Radiation Facility SURF III are perfect sources for radiometric applications, because the output spectrum can be custom-tailored to the user's needs: Low current operations can simulate the solar spectrum, changes to the electron energy can deal with higher-order contributions of spectrometers and monochromators, and manipulation of the source size increases the lifetime or change the radiation density. At multi-user facilities these special operational conditions are generally not possible, since many users have to be satisfied simultaneously. NIST maintains at SURF one of the best SR-based calibration programs in the world: Standard lamp calibrations, detector calibrations, and measurements of optical properties are routinely performed at SURF with great reliability and accuracy. More information about SURF can be found at: http://physics.nist.gov/surf [Preview Abstract] |
Tuesday, February 16, 2010 2:42PM - 2:54PM |
Y13.00007: Impact of Radiation in Critical Organs in Radiotherapy Treatment of Breast and Lung Cancers Anil Pyakuryal, Chiu-Hao Chen, Sudarshan Dhungana Various 3D conformal radiotherapy (3DCRT) techniques are commonly used in the treatment of cancerous tumors at appropriate prescription doses (PDs). The purpose of this study was to analyze the impact of radiation in heart and lungs in left breast and left lung cancer patients treated using 3DCRT techniques. Treatment plans for the eight breast cancer patients (n=8), eight lung cancer patients at early stage (m=8), and eight lung cancer patients at stage II and III (k=8) were evaluated. Relative complication probabilities (RCPs) for the irradiated organs were computed from the plans using \textbf{\textit{HART}} [Med. Phys. 36, p.2547 (2009)] program at PD. The RCPs were found to be (i) 2.3{\%} (n=8, PD=56 Gy), 6.4{\%} (m=8, PD=30.7 Gy), and 16.7{\%} (k=8, PD=54.8 Gy) for the heart, (ii) 1{\%} (n=6, PD=58.4 Gy) for the left lung, and (iii) 7{\%} (m=6, PD=31 Gy) and 5.3{\%} (k=8, PD=54.8 Gy) for the whole lung. Homogeneous target coverage and improved dose conformality were the major advantages in the treatment of breast cancer. Therefore, simple 3DCRT based whole-breast irradiation and partial lung treatment techniques can offer promising results while adequately sparing the organs in the treatment of breast and lung cancers. [Preview Abstract] |
Tuesday, February 16, 2010 2:54PM - 3:06PM |
Y13.00008: Standoff Detection of Nitro Compounds Using Ultrashort Laser Induced Breakdown Spectroscopy Tariq Ahmido, Antonio Ting, Prabhakar Misra Ultrashort Laser-Induced Breakdown Spectroscopy (LIBS) is being used for the analysis of contaminants on surfaces. In this technique, emission radiation from the breakdown of surface contaminants is spectrally investigated. An ultra short laser pulse ($\sim $50 fs) produced by a Ti: Sapphire chirped pulse amplification laser at a wavelength of 800 nm is used. The large bandwidth associated with this laser allows it to be propagated and focused transversely and longitudinally at standoff distances to initiate the LIBS. Analysis of the return signatures from remote target locations can indicate the presence of undesirable chemical compounds. The application of this research is to detect surface chemical compounds, such as pollutants and molecules containing the nitro group NOx. The research focuses on the detection of molecular fragments present in the plasma, which are generated when the laser breaks down the surface. Aspects of generation, detection, and analysis of ultrashort pulse LIBS detection of chemical contaminants will be presented. [Preview Abstract] |
Tuesday, February 16, 2010 3:06PM - 3:18PM |
Y13.00009: Radiation Dosimetry of Dental Enamel Using X-Band and Q-Band EPR Spectroscopy Tania De, Alex Romanyukha, Barry Pass, Prabhakar Misra Electron paramagnetic resonance (EPR) dosimetry of tooth enamel can be used for individual dose reconstruction following radiation accidents. The purpose of this study was to develop a rapid, minimally invasive technique for obtaining a sample of dental enamel small enough to not disturb the structure and functionality of a tooth and to improve the sensitivity of the spectral signals using X-band (9.4 GHz) and Q-band (34 GHz) EPR spectroscopy. EPR measurements in X-band were performed on 100 mg isotropic powdered enamel samples and Q-band measurements done on 4 mg (1x1x3 mm) enamel biopsy samples. All samples were obtained from discarded teeth collected during normal dental treatment. In order to study the variation of the Radiation-Induced Signal (RIS) at different orientations in the applied magnetic field samples were placed in the resonance cavity for Q-band EPR. In X-band spectra, the RIS is distinct from the ``native'' radiation-independent signal only for doses $>$ 0.5Gy. Q-band, however, resolves the RIS and ``native'' signals and improves sensitivity by a factor of 20 enabling measurements in 2-4 mg tooth enamel samples. [Preview Abstract] |
Tuesday, February 16, 2010 3:18PM - 3:30PM |
Y13.00010: Electron-Beam Noise and spontaneous emission Suppression and the Fundamental Coherence Limits of Free Electron Radiators Avraham Gover It is shown that the electron beam current noise can be reduced at optical frequencies below the classical shot-noise limit. This self-ordering phenomenon takes place due to longitudinal collective Coulomb interaction when the beam parameters are set to excite Langmuir plasma-wave single mode oscillation [1]. Full 3-D particle dynamics simulations confirm the theoretical model. Based on this result, it is shown that it is possible to obtain sub-radiance (in the sense of Dicke [2]) of spontaneous emission from electron-beam radiators. This results in fundamental limit expressions for the coherence of FELs and other e-beam radiators, analogously to the Schawlow-Towns limit [3]. Surpassing the shot-noise limit, the coherence of free electron laser radiation is limited by the e-beam energy spread at frequencies below the IR, and fundamentally limited by quantum noise at higher frequencies. [Preview Abstract] |
Tuesday, February 16, 2010 3:30PM - 3:42PM |
Y13.00011: The Orbital Gyromagnetic Factor of Relativistic Electrons Ayodeji Awobode An analog of the Bargmann-Michel-Telegdi (BMT) equation which describes the motion of the spin four-vector S is derived for the orbital magnetic moment L. It is shown that in addition to the term in dL/dt describing the precession of the orbital angular momentum in a magnetic field, there appears a term which may imply the possibility of an anomalous contribution to the orbital g-factor g$_{L}$. Experiments to measure the anomaly are discussed. [Preview Abstract] |
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