Neutron Shielding Effectiveness Of Multifunctional Composite Materials,
2013
Air Force Institute of Technology
Neutron Shielding Effectiveness Of Multifunctional Composite Materials, Anthony D. Marchand
Theses and Dissertations
Composite materials offer a greater degree of flexibility in design and engineering of specialized space vehicle shielding applications compared to aluminum. A new design for shielding materials has been developed by including specific neutron absorbers and conductive materials into the composite structure. In this research, the neutron shielding capability of two types of custom-designed nanocomposite materials are compared to that of T6061 aluminum.
Passive, Low Cost Neutron Detectors For Neutron Diagnostics At The National Ignition Facility,
2013
Air Force Institute of Technology
Passive, Low Cost Neutron Detectors For Neutron Diagnostics At The National Ignition Facility, Nathaniel C. Loyd
Theses and Dissertations
Experimental validation of neutron fluence models of fusion events at the National Ignition Facility is necessary to predict radiation damage to measurement electronics. Due to programmatic and facility limitations, traditional neutron measurement techniques are not well suited for this application. Notably, a low cost and passive measurement technique that provides a permanent record is preferred. A detector was designed using gadolinium oxide contained within an aluminum reservoir. The reservoir is secured by a thin layer of Mylar and x-ray film, and vacuum sealed in a light tight package. In the presence of a thermal neutron flux, the gadolinium atoms absorb …
Analysis Of A Van De Graaff Generator For Emp Direct Current Survivability Testing,
2013
Air Force Institute of Technology
Analysis Of A Van De Graaff Generator For Emp Direct Current Survivability Testing, Robert J. Kress
Theses and Dissertations
The direct current produced from the Van de Graaff (VDG) at the Air Force Research Laboratory (AFRL) has been measured and analyzed. The current pulse produced from the VDG is oscillatory. Experimental data show complete damping occurs after 8 oscillations and within 10-6 seconds. The spark gap distance and circuit resistance were varied to determine if the circuit could convert to an overdamped RLC circuit in order to reduce the oscillations. The data establishes that the VDG produces at least 3 full wave Fourier frequencies of: 3, 7, and 15 MHz ± 2.0 MHz, while the first oscillation had …
Depth-Resolved Cathodoluminescence Of Tho2,
2013
Air Force Institute of Technology
Depth-Resolved Cathodoluminescence Of Tho2, Michael G. Lee
Theses and Dissertations
Single crystal thorium dioxide (ThO2) samples were hydrothermally grown and studied using depth-resolved cathodoluminescence (CL) to characterize the surface and bulk electronic states. X-ray diffraction (XRD) measurements were collected to confirm that these crystals were ThO2 in the fluorite structure. Understanding the chemical and structural quality of ThO2 will aid in the fabrication of better neutron detectors as well as in the power production with thorium breeder reactors. Monte Carlo simulations predicted the expected energy-dependent electron interaction depths in the ThO2 crystals. CL was conducted with electron energy range of 1.5 - 12 keV, a …
Three Dimensional Positron Annihilation Momentum Spectroscopy Of Lithium Tetraborate Crystals,
2013
Air Force Institute of Technology
Three Dimensional Positron Annihilation Momentum Spectroscopy Of Lithium Tetraborate Crystals, Stefan B. Fagan-Kelly
Theses and Dissertations
Previous endeavors in positron annihilation spectroscopy (PAS) at AFIT have resulted in the design and characterization of a second-generation three-dimensional positron annihilation momentum spectroscopy system (3DPAMSS) which combines two-dimensional angular correlation of annihilation radiation (2D ACAR) and coincident Doppler broadening of annihilation radiation (CDBAR) in order to measure electron momentum distributions in samples and thus characterize material defects. The focus of this particular research is to nondestructively measure negative defects in the crystal lattice of copper-doped, silver-doped, and undoped lithium tetraborate by 3DPAMSS spectroscopy using a Na-22 source and two high-purity germanium (HPGe) position-resolvable strip detectors. Lithium tetraborate is a …
Modeling Sodium Iodide Detector Response Using A Parametric Equations,
2013
Air Force Institute of Technology
Modeling Sodium Iodide Detector Response Using A Parametric Equations, Neeraj Sethi
Theses and Dissertations
This research utilizes the relationship between source location, background radiation and detector placement to quantify an expected detector response from a 3x3 Sodium Iodide gamma detector. A parametric equation is developed to calculate the detector response as a function of distance and source photon energy. Using MCNP particle current and pulse height tally functions, backscattering photons are quantified as a function of material thickness and energy distribution. Three configurations of source - detector - scattering medium were modeled in MCNP using the pulse height tally functions, integrated over a 70keV - 360keV energy window and plotted as a function of …
Changes To Tensile Strength And Electromagnetic Shielding Effectiveness In Neutron Irradiated Carbon Nanocomposites,
2013
Air Force Institute of Technology
Changes To Tensile Strength And Electromagnetic Shielding Effectiveness In Neutron Irradiated Carbon Nanocomposites, James F. Shinn
Theses and Dissertations
Electromagnetic interference shielding effectiveness (EMI-SE) and tensile strength of nanocomposites containing multi-walled carbon nanotubes (MWNTs) are investigated following neutron irradiation. This nanocomposite material consists of two plies of MWNTs in an epoxy resin, and 4 plies of an E-glass substrate. EMI-SE measurements over the X-band frequency spectrum and monotonic tension tests to determine Young’s Modulus were performed before and after irradiation on the nanocomposite material. The nanocomposite and the MWNT plies were irradiated to a total fluence of 1.4 × 1014 1 MeV (Si-eq) n/cm2. The nanocomposites showed an average increase of 8 dB in shielding effectiveness …
Solving Point-Reactor Kinetics Equations Using Exponential Moment Methods,
2013
Air Force Institute of Technology
Solving Point-Reactor Kinetics Equations Using Exponential Moment Methods, Paul M. Thelen
Theses and Dissertations
A robust method of solving the reactor point kinetic equations was designed using exponential moment methods. Although the method requires a relatively large number of calculations to complete, the accuracy ensured by each individual step calculation allows larger time steps to be used. The algorithm designed was verified to converge to the correct value as step size was reduced. Additionally, the algorithm can take steps much larger than the average neutron lifetime while maintaining some precision. An error control scheme was designed based on changes observed in the results as a function of time step size. The error control adaptively …
Superfluidity In Neutron Stars,
2013
Washington University in St Louis
Superfluidity In Neutron Stars, Samuel J. Witte
Undergraduate Theses—Unrestricted
Nucleon pairing is studied with specific considerations directed toward the possible influence on neutron star cooling. We present an in-depth analysis of BCS theory using realistic nuclear potentials and consider the impact short-range correlations can have on the gap. Gap calculations are incorporated into neutron star cooling simulations and the significance of the 3P2 −3F2 channel in various hadronic cooling models is closely examined. An analysis of the 1S0 gap in neutron matter suggests short-range correlations can drastically alter the magnitude, density range, and temperature dependence of the gap. While the newly constructed 1S0 gap does not significantly alter the …
Density Functional Theory And The Calculation Of Tcmg2O4 Spinel Lattice Parameters,
2013
California Polytechnic State University - San Luis Obispo
Density Functional Theory And The Calculation Of Tcmg2O4 Spinel Lattice Parameters, Jon Karlo Macias
Physics
The cohesive energy, lattice constant and bulk modulus of two simple HCP crystal structures of magnesium and technetium were calculated using the vienna ab initio simulation package (VASP) which is based on density functional theory (DFT). The same properties were determined for TcMg2O4 spinel. The theoretical results of the lattice constant of the pure crystals were compared to experimental results and found to be in excellent agreement with a difference of less than 2%. The results for the lattice constant of the TcMg2O4 spinel were found to be in excellent agreement as well with …
Second Order And Fluctuating Hydrodynamic Theory Of Two-Particle Transverse Momentum Correlations In Nuclear Collisions,
2013
Wayne State University
Second Order And Fluctuating Hydrodynamic Theory Of Two-Particle Transverse Momentum Correlations In Nuclear Collisions, Rajendra Kumar Pokharel
Wayne State University Dissertations
Relativistic heavy ion collision experiments show clear evidence of creation of a very short-lived phase of nuclear matter consisting of color-deconfined quarks and gluons. This matter is known as the quark-gluon plasma (QGP). Fluctuation and correlation measurements of the detected particles have played a very important role in revealing the properties of QGP. In particular, these measurements have shown that the QGP behaves like a nearly perfect liquid. Relativistic hydrodynamics has been successfully used to study how the QGP evolves before the system hadronizes and ultimately produces the final state particles. Transport properties like shear viscosity constitute an important part …
Exclusive Deeply Virtual Compton And Neutral Pion Cross-Section Measurements In Hall C,
2013
Jefferson Lab
Exclusive Deeply Virtual Compton And Neutral Pion Cross-Section Measurements In Hall C, A. Camsonne, S. Covrig, R. Ent, D. Gaskell, F. X. Girod, M. Jones, C. Keppel, P. Nadel-Turoński, A. J. R. Puckett, B. Sawatzky, P. Solvignon, S. A. Wood, B. Wojtsekhowski, A. Asaturyan, A. Mkrtchyan, H. Mkrtchyan, V. Tadevosyan, S. Zhamkochyan, M. Boer, C. Desnault, R. Dupré, B. Garillon, M. Guidal, M. Hattawy, H. S. Jo, M. Defurne, M. Garçon, F. Sabaié, I. Albayrak, M. Carmignotto, J. Denés-Couto, N. Hlavin, T. Horn, F. Klein, B. Nepal, M. Canan, C. Hyde, M. N. H. Rashad, P. King, J. Roche, M. Ben Ali, L. Ghedira, M. Mazouz, A. Fradi, D. Day, D. Keller, O. Rondon, J.R.M. Annand, D. J. Hamilton, S. Sirca, M. Elaasar, G. Huber, F. Wesselman, P. E. C. Markowitz, A. Ahmidouch, S. Danagoulian, M. H. Shabestari, D. Androic, C. Chen, Y. Han, P. Gueye, L. Tang, V. Sulkosky
Physics Faculty Publications
We propose to use the High Momentum Spectrometer of Hall C combined with a PbWO₄ electromagnetic calorimeter in order to perform high precision measurements of the Deeply Virtual Compton Scattering (DVCS) cross section. A wide range of kinematics accessible with an 11 GeV electron beam off an unpolarized proton target will be covered. The azimuthal, energy and helicity dependences of the cross section will all be exploited in order to separate the interference and DVCS² contributions to each of the Fourier moments of the cross section. For each term, its Q² dependence will be measured independently. At the same time, …
Single Spin Asymmetry An In Polarized Proton–Proton Elastic Scattering At √S = 200 Gev,
2013
Old Dominion University
Single Spin Asymmetry An In Polarized Proton–Proton Elastic Scattering At √S = 200 Gev, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, C. D. Anson, D. Arkhipkin, E. Aschenauer, S. Bültmann, I. Koralt, D. Plyku
Physics Faculty Publications
We report a high precision measurement of the transverse single spin asymmetry AN at the center of mass energy √s = 200 GeV in elastic proton–proton scattering by the STAR experiment at RHIC. The AN was measured in the four-momentum transfer squared t range 0.003 ⩽ | t | ⩽ 0.035 ( GeV / c ) 2 , the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of AN and its t-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the …
Beam Asymmetry Σ For Π+ And Π0 Photoproduction On The Proton For Photon Energies From 1.102 To 1.862 Gev,
2013
Old Dominion University
Beam Asymmetry Σ For Π+ And Π0 Photoproduction On The Proton For Photon Energies From 1.102 To 1.862 Gev, K. P. Adhikari, D. Adikaram, M. J. Amaryan, C. S. Nepali, Y. Prok, Clas Collaboration
Physics Faculty Publications
Beam asymmetries for the reactions ˠp -> pπ0 and ˠp -> nπ+have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged, linearly polarized photon beam with energies from 1.102-1.862 GeV. A Fourier moment technique for extracting beam asymmetries from experimental data is described. The results reported here possess greater precision and finer energy resolution than previous measurements. Our data for both pion reactions appear to favor the SAID and Bonn-Gatchina scattering analyses over the older Mainz MAID predictions. After incorporating the present set of beam asymmetries into the world database, exploratory fits made with …
Cross Sections For The Ɣp → K*+Ʌ And Ɣp → K*+Σº Reactions Measured At Clas,
2013
Old Dominion University
Cross Sections For The Ɣp → K*+Ʌ And Ɣp → K*+Σº Reactions Measured At Clas, K.P. Adhikari, M. J. Amaryan, C. E. Hyde, S. Koirala, M. Mayer, Clas Collaboration
Physics Faculty Publications
The first high-statistics cross sections for the reactions ɣp → K*+Ʌ and ɣp → K*+Σº were measured using the CLAS detector at photon energies between threshold and 3.9 GeV at the Thomas Jefferson National Accelerator Facility. Differential cross sections are presented over the full range of the center-of-mass angles, and then fitted to Legendre polynomials to extract the total cross section. Results for the K*+Ʌ final state are compared with two different calculations in an isobar and a Regge model, respectively. Theoretical calculations significantly underestimate the K*+Ʌ total cross sections between 2.1 and 2.6 GeV, but are in better agreement …
Experimental Studies Of Di-Jets In Au + Au Collisions Using Angular Correlations With Respect To Back-To-Back Leading Hadrons,
2013
Old Dominion University
Experimental Studies Of Di-Jets In Au + Au Collisions Using Angular Correlations With Respect To Back-To-Back Leading Hadrons, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Koralt, Star Collaboration
Physics Faculty Publications
Jet-medium interactions are studied via a multihadron correlation technique ( called "2 + 1"), where a pair of back-to-back hadron triggers with large transverse momentum is used as a proxy for a di-jet. This work extends the previous analysis for nearly symmetric trigger pairs with the highest momentum threshold of trigger hadron of 5 GeV/c with the new calorimeter-based triggers with energy thresholds of up to 10 GeV and above. The distributions of associated hadrons are studied in terms of correlation shapes and per-trigger yields on each trigger side. In contrast with di-hadron correlation results with single triggers, the associated …
Elliptic Flow Of Identified Hadrons In Au + Au Collisions At √ˢᴺᴺ = 7.7- 62.4 Gev,
2013
Old Dominion University
Elliptic Flow Of Identified Hadrons In Au + Au Collisions At √ˢᴺᴺ = 7.7- 62.4 Gev, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, S. Bültmann, Star Collaboration
Physics Faculty Publications
Measurements of the elliptic flow, υ2, of identified hadrons (π±, , K±, , KOs, p, p¯, ɸ, Λ, Λ¯, Ξ-, Ξ¯+, Ω-, Ω¯+ in Au + Au collisions at √ˢᴺᴺ = 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV are presented. The measurements were done at midrapidity using the time-projection chamber and the time-of-flight detectors of the Solenoidal Tracker at RHIC experiment during the beam-energy scan program at Relativistic Heavy Ion Collider. A significant difference in the υ2 values for particles and the corresponding antiparticles was observed at all transverse momenta for …
Deep Exclusive Π+ Electroproduction Off The Proton At Clas,
2013
Old Dominion University
Deep Exclusive Π+ Electroproduction Off The Proton At Clas, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, G. E. Dodge, S. E. Kuhn, M. Mayer, C. S. Nepali, H. Seraydaryan, L. B. Weinstein, J. Zhang
Physics Faculty Publications
The exclusive electroproduction of π + above the resonance region was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory by scattering a 6GeV continuous electron beam off a hydrogen target. The large acceptance and good resolution of CLAS, together with the high luminosity, allowed us to measure the cross section for the γ * p → nπ + process in 140 (Q 2, x B , t) bins: 0.16 < x B < 0.58, 1.6 GeV2 < Q 2 < 4.5 GeV2 and 0.1 GeV2 < −t < 5.3 GeV2. For most bins, the statistical accuracy is on the order of a …
Measurement Of Transparency Ratios For Protons From Short-Range Correlated Pairs,
2013
Old Dominion University
Measurement Of Transparency Ratios For Protons From Short-Range Correlated Pairs, Clas Collaboration, L. B. Weinstein, K. P. Adhikari, M. J. Amaryan, H. Baghdasaryan, G. E. Dodge, C. E. Hyde, S. E. Kuhn, M. Mayer, H. Seradaryan
Physics Faculty Publications
Nuclear transparency, Tp(A), is a measure of the average probability for a struck proton to escape the nucleus without significant re-interaction. Previously, nuclear transparencies were extracted for quasi-elastic A(e,e′p) knockout of protons with momentum below the Fermi momentum, where the spectral functions are well known. In this Letter we extract a novel observable, the transparency ratio, Tp(A)/Tp(12C), for knockout of high-missing-momentum protons from the breakup of short-range correlated pairs (2N-SRC) in Al, Fe and Pb nuclei relative to C. The ratios were measured at momentum transfer Q2 ⩾1.5(GeV/c)2 and x …
Transverse Polarization Of Σ+ (1189) In Photoproduction On A Hydrogen Target In Clas,
2013
Old Dominion University
Transverse Polarization Of Σ+ (1189) In Photoproduction On A Hydrogen Target In Clas, Clas Collaboration, C. S. Nepali, M. Amaryan, K. P. Adhikari, H. Baghdasaryan, S. Bültmann, N. Guler, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, B. Torayev, L. B. Weinstein
Physics Faculty Publications
Experimental results on the Σ+(1189) hyperon transverse polarization in photoproduction on a hydrogen target using the CLAS detector at Jefferson Laboratory are presented. The Σ+(1189) was reconstructed in the exclusive reaction γ+p→K0S+Σ+(1189) via the Σ+→pπ0 decay mode. The K0S was reconstructed in the invariant mass of two oppositely charged pions with the π0 identified in the missing mass of the detected pπ+π− final state. Experimental data were collected in the photon energy range Eγ=1.0 –3.5 GeV (√s range 1.66–2.73 GeV). We observe a large negative polarization …
