Nuclear Commons^™

Neutron Detection Using Amorphous Boron-Carbide Hetero-Junction Diodes, Thomas P. Mcquary

Theses and Dissertations

The high energy products of the ¹⁰B(n,α)⁷Li neutron capture reaction were explored as a means of thermal neutron detection in thin film amorphous boron carbide (a--B₅C:H_x) on n-type silicon hetero-junction diodes. Pulse height spectroscopy was conducted on the diodes while they were subjected to a moderated plutonium-beryllium (PuBe) source. Neutron capture could not be confirmed experimentally in any of the devices tested. Device modeling was performed to investigate the cause for the diode detector's negative response. A 1.47 MeV α particle produced transient current of 10^-7 A and the induced was 4.7 …

Measurement Of The Generalized Form Factors Near Threshold Via Γ*P→Nπ+ At High Q2, K. Park, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We report the first extraction of the pion-nucleon multipoles near the production threshold for the nπ⁺ channel at relatively high momentum transfer (Q² up to 4.2 GeV²). The dominance of the s-wave transverse multipole (E₀₊), expected in this region, allowed us to access the generalized form factor G₁ within the light-cone sum-rule (LCSR) framework as well as the axial form factor G_A. The data analyzed in this work were collected by the nearly 4π CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754-GeV electron beam on a proton …

National Center For Nuclear Security, Veraun Chipman, Amanda Klingensmith, Cathy Snelson

NSTec UNLV Symposium

National Center for Nuclear Security (NCNS) Mission

•Chartered mission is to enhance the Nation’s verification and detection capabilities in support of nuclear arms control and nonproliferation through R&D activities at the NNSS
•Three focus areas
–Treaty Verification Technologies
–Nonproliferation Technologies
–Technical Nuclear Forensics

Development Of Ion Beam Nuclear Transmutation Doping (Ibntd) For Novel Electronics In Extreme Conditions, Michael G. Pravica, Noel A. Guardala, Jack L. Price

NSTec UNLV Symposium

Development of IBNTD for electronics under extreme conditions.

•We hope to create novel wide bandgap devices using Ion Beam Nuclear Transmutation Doping (IBNTD). These devices may be used as rugged high power switches, and high current/low noise amplifiers. Diamond in itself represents a “Holy Grail” for electrical applications due to its very high thermal conductivity and excellent electrical characteristics.
•We also hope to develop devices that can convert the enormous energy from high-energy nuclear particles (α2+,β-,β+, γparticles) into useful electricity and thus harness the enormous energy still contained in “spent” nuclear fuel. Developing these direct energy conversion (DEC) devices would …

Overview Of Nstec Plasma Focus Tubes And Magnetohydrodynamic Modeling Capabilities, Tim Meehan

NSTec UNLV Symposium

•Brief Description of how DPFs work, in general what they are useful for.
•DPF devices that we have at NSTec
•Using MHD modeling software to optimize designs and predict performance
•Neutron Resonance Spectroscopy

Utilizing (P,D) And (P,T) Reactions To Obtain (N,F) Cross Sections In Uranium Nuclei Via The Surrogate-Ratio Method, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Escher, J. Munson, L. Phair, J. J. Ressler

Physics Faculty Publications

The surrogate ratio method has been tested for (p,d) and (p,t) reactions on uranium nuclei. ²³⁶U and ²³⁸U targets were bombarded with 28-MeV protons and the light ion recoils and fission fragments were detected using the Silicon Telescope Array for Reaction Studies detector array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The (p,df) reaction channels on ²³⁶U and ²³⁸U targets were used as a surrogate to determine the σ[²³⁶U(n,f)]/σ[²³⁴U(n, …

Upper Limits For The Photoproduction Cross Section For The Φ−−(1860) Pentaquark State Off The Deuteron, H. Egiyan, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We searched for the Φ^--(1860) pentaquark in the photoproduction process off the deuteron in the Ξ^-π^--decay channel using CLAS. The invariant-mass spectrum of the Ξ^-π^- system does not indicate any statistically significant enhancement near the reported mass M = 1.860 GeV. The statistical analysis of the sideband-subtracted mass spectrum yields a 90%-confidence-level upper limit of 0.7 nb for the photoproduction cross section of Φ^--(1860) with a consecutive decay into Ξ^-π^- in the photon-energy range 4.5 GeV < E_γ < 5.5 GeV.

Boost-Invariant (2+1)-Dimensional Anisotropic Hydrodynamics, Mauricio Martinez, Radoslaw Ryblewski, Michael T. Strickland

Physics and Astronomy Faculty Publications

We present results of the application of the anisotropic hydrodynamics (aHydro) framework to (2+1)-dimensional boost-invariant systems. The necessary aHydro dynamical equations are derived by taking moments of the Boltzmann equation using a momentum-space anisotropic one-particle distribution function. We present a derivation of the necessary equations and then proceed to numerical solutions of the resulting partial differential equations using both realistic smooth Glauber initial conditions and fluctuating Monte Carlo Glauber initial conditions. For this purpose we have developed two numerical implementations: one that is based on straightforward integration of the resulting partial differential equations supplemented by a two-dimensional weighted Lax-Friedrichs smoothing …

A Shell Model Study Of The High Spin States Of 88Y, M. Bunce, P. H. Regan, V. Werner, A. Anagnostatou, C. W. Beausang, M. Bowry, R. J. Casperson, D. Chen, N. Cooper, P. Goddard, R. O. Hughes, G. Ilie, P.J.R. Mason, B. Pauerstein, M. W. Reed

Physics Faculty Publications

Experiments were carried out at the Wright Nuclear Structure Laboratory at Yale University using the 21MV ESTU Tandem Van de Graaff accelerator with the purpose of studying ⁸⁸Y. A beam of ¹⁸O impinged at laboratory energies of 60, 65 and 70 MeV on a 600 μg/cm ^{2 74}Ge target with a thick (10mg/cm ²) ¹⁹⁷Au backing. This experiment was performed with the specific aim of accessing medium spin states of the nucleus of interest. A second experiment was undertaken to populate the nucleus of interest in higher spin states by impinging the same ^{18 …}

To The Continuum And Beyond: Structure Of U Nuclei, R. O. Hughes, C. W. Beausang, T. J. Ross, J. T. Burke, N. D. Scielzo, M. S. Basunia, C. M. Campbell, R. J. Casperson, H. L. Crawford, J. Munson, L. Phair, J. J. Ressler

Physics Faculty Publications

An experiment was performed at the 88-inch cyclotron at LBNL to investigate the structure of uranium isotopes and concurrently test the so-called surrogate ratio method. A 28 MeV proton beam was used to bombard ²³⁶U and ²³⁸U targets and the outgoing light ions were detected using the STARS silicon telescope allowing isotopic assignments and the excitation energy of the compound nucleus to be measured. A fission detector was placed at backward angles to give particle-fission coincidences, while the six clover germanium detectors of the LIBERACE array were used for particle-γ coincidences. The (p,d) reaction channels on ²³⁶U …

Observation Of A Narrow Structure In 1H(Ykso)X Via Interference With Φ-Meson Production, M. J. Amaryan, G. Gavalian, C. Nepali, M. V. Polyakov, W. J. Briscoe, G. E. Dodge, C. E. Hyde, F. Klein, V. Kuznetsov, I. Strakovsky, J. Zhang

Physics Faculty Publications

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width σ = 6 MeV in the missing mass of K_S in the reaction γ+p → pK_SK_L. The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pK_L system and the φ(K_SK_L) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the φ-production-based background-only hypothesis …

Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E'Pp)N, H. Baghdasaryan, L. B. Weinstein, J. M. Laget, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, J. Ball, M. Battaglieri, A. S. Biselli, G. Dodge, C. E. Hyde, S. E. Kuhn, H. Seraydaryan

Physics Faculty Publications

Measuring nucleon-nucleon short range correlations (SRCs) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wave function, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the ³He(e,e'pp)n reaction, looking at events with high-momentum protons (p_p > 0.35 GeV/c) and a low-momentum neutron (p …

Evidence For The Onset Of Color Transparency In Ρ0 Electroproduction Off Nuclei, L. El Fassi, L. Zana, H. Hafidi, M. Holtrop, B. Mustapha, W. K. Brooks, H. Hakobyan, Z. Zheng, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein

Physics Faculty Publications

We have measured the nuclear transparency of the incoherent diffractive A( e , e ′ ρ⁰ ) process in ¹²C and ⁵⁶Fe targets relative to ²H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ⁰ ʼs on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (lc), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q²). While the transparency for both ¹²C and ⁵⁶Fe …

Anomalous Centrality Evolution Of Two-Particle Angular Correlations From Au-Au Collisions At √ˢᴺᴺ = 62 And 200 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration

Physics Faculty Publications

We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity η and ϕ for charged particles from Au-Au collisions at √ˢᴺᴺ = 62 and 200 GeV with transverse momentum p_t ≥ 0.15 GeV/c, │η│ ≤ 1, and 2 π in azimuth. Observed correlations include a same-side (relative azimuth <π/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the η width of the same-side 2D peak also increases rapidly (η elongation), and the ϕ width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here.

Energy And System Size Dependence Of Two- And Four-Particle Ν2 Measurements In Heavy-Ion Collisions At √ˢᴺᴺ = 62.4 And 200 Gev And Their Implications On Flow Fluctuations And Nonflow, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, M. Bueltmann, Star Collaboration

Physics Faculty Publications

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants ν₂ ν₂{2} and ν₂{4}) for Au + Au and Cu + Cu collisions at center-of-mass energies √ˢᴺᴺ = 62.4 and 200 GeV. The difference between ν₂{2}² and ν₂{4}² is related to ν₂fluctuations (σ_ν2) and nonflow (δ₂). We present an upper limit to σ_ν2/ν₂. Following the assumption that eccentricity fluctuations σ_ε dominate ν₂ fluctuations σ_ν2/ν_{2 ≈ σε/ε} we …

Directed And Elliptic Flow Of Charged Particles In Cu + Cu Collisions At √ˢᶰᶰ =22.4 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, X. Zhu, Star Collaboration

Physics Faculty Publications

This paper reports results for directed flow v₁ and elliptic flow v₂ of charged particles in Cu + Cu collisions at √ˢᶰᶰ = 22.4 GeV at the Relativistic Heavy Ion Collider. The measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4-GeV Cu + Cu collisions the prior observation that v₁ is independent of the system size at 62.4 and 200 GeV and also extend the scaling of v₁ with η/y_beam to this system. The measured v₂p_T in Cu + Cu …

Di-Electron Spectrum At Mid-Rapidity In P+P Collisions At √S=200 Gev, L. Adamczyk, S. Bueltmann, I. Koralt, D. Plyku, Y. Zoulkarneeva, Star Collaboration

Physics Faculty Publications

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e⁺e^- decays, from √s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω → e⁺e^- invariant yields are consistent with previous measurements. The mid-rapidity …

Virtual Compton Scattering And The Generalized Polarizabilities Of The Proton At Q2 = 0.92 And 1.76 Gev2, H. Fonvielle, G. Laveissiere, N. Degrande, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein

Physics Faculty Publications

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep → epγ. This paper gives a detailed account of the analysis which has led to the determination of the structure functions P_LL − P_TT/ε and P_LT and the electric and magnetic generalized polarizabilities (GPs) α_E(Q²)and β_M(Q²) at values of the four-momentum transfer squared Q² = 0.92 and 1.76 GeV². These data, together with the results of VCS experiments at lower momenta, help building a …

System Size And Energy Dependence Of Near-Side Dihadron Correlations, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, S. Bueltmann, I. Koralt, D. Plyku

Physics Faculty Publications

Two-particle azimuthal (Δφ) and pseudorapidity (Δη) correlations using a trigger particle with large transverse momentum (PT)in d+Au, Cu+Cu, and Au+Au collisions at √ sNN = 62.4 GeV and 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider are presented. The near-side correlation is separated into a jet-like component, narrow in both Δφ and Δη, and the ridge, narrow in Δφ but broad in Δη. Both components are studied as a function of collision centrality, and the jet-like correlation is studied as a function of the trigger and associated PT. The behavior of the …

Measurement Of Exclusive Πº Electroproduction Structure Functions And Their Relationship To Transverse Generalized Parton Distributions, Clas Collaboration, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, S. Koirala, S. E. Kuhn, M. Mayer, L. B. Weinstein, I. Bedlinsky, V. Kubarovsky

Physics Faculty Publications

Exclusive π⁰ electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q², x_B , t , and ϕπ , in the Q² range from 1.0 to 4.6  GeV² , −t up to 2  GeV² , and x_B from 0.1 to 0.58. Structure functions σ_T+ϵσ_L , σ_TT , and σ_LT were extracted as functions of t for each of 17 combinations of Q² and x_B . …

Comment On “Observation Of A Narrow Structure In 1H(Γ,KS0)X Via Interference With Φ-Meson Production”, M. Anghinolfi, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

In Ref. [1], the authors claim to observe a narrow structure in the mass spectrum constructed from the (pKL) system using data from the CLAS detector. The interpretation of this narrow structure given in Ref. [1] is as follows: “It may be due to the photoproduction of the Θ⁺pentaquark or some unknown Σ* resonance.” The authors go on to say that “it is unlikely for the observed structure to be due to a Σ* resonance.”

Hrc Enews — 2012 Winter, Megan M. Iudice

Publications (HRC)

This issue contains staff accomplishments and announcements, event listings, and a "new faces" listing for new staff, affiliates, and researchers.

Inclusive Charged Hadron Elliptic Flow In Au + Au Collisions At √ˢᴺᴺ = 7.7-39 Gev, L. Adamczyk, G. Agakishiev, S. Bültmann, I Koralt, D. Plyku, Star Collaboration

Physics Faculty Publications

A systematic study is presented for centrality, transverse momentum p_T, and pseudorapidity (η) dependence of the inclusive charged hadron elliptic flow v₂ at midrapidity (|η| < 1.0) in Au + Au collisions at √ˢᴺᴺ = 7.7, 11.5, 19.6, 27, and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and four-particle cumulants (v₂{4}), are presented to investigate nonflow correlations and v₂ fluctuations. We observe that the difference between v₂{2} and v₂{4} is smaller at the lower collision energies. Values of v₂, scaled by the initial coordinate space eccentricity, v₂/ϵ, as a function of p_T are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results …

Ρ0 Photoproduction In Auau Collisions At √ Snn = 62.4 Gev Measured With The Star Detector, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, S. Bueltmann, I. Koralt, D. Plyku

Physics Faculty Publications

Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent ρ⁰ photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent ρ0 photoproduction with nuclear breakup is 10.5 ± 1.5 ± 1.6mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is 4.4 ± 0.6, …

Spectroscopic Methods Of Process Monitoring For Safeguards Of Used Nuclear Fuel Separations, Jamie Lee Warburton

UNLV Theses, Dissertations, Professional Papers, and Capstones

To support the demonstration of a more proliferation-resistant nuclear fuel processing plant, techniques and instrumentation to allow the real-time, online determination of special nuclear material concentrations in-process must be developed. An ideal materials accountability technique for proliferation resistance should provide nondestructive, realtime, on-line information of metal and ligand concentrations in separations streams without perturbing the process. UV-Visible spectroscopy can be adapted for this precise purpose in solvent extraction-based separations.

The primary goal of this project is to understand fundamental URanium EXtraction (UREX) and Plutonium-URanium EXtraction (PUREX) reprocessing chemistry and corresponding UV-Visible spectroscopy for application in process monitoring for safeguards. By …

Lunar Occultation Observer: A Nuclear Astrophysics All-Sky Survey Mission Concept, Riley Freelove

Von Braun Symposium Student Posters

No abstract provided.

Source Normalization Constants For Ground Distributed Fallout Fields, Justin M. Smith

Theses and Dissertations

Five assumptions regarding a first order model developed to calculate dose rate at a detector above a fallout field are analyzed. The omission of scattering is relaxed by the method of successive scatters resulting in a build up factor of 1.1. The use of a single average photon energy to represent a fallout distribution is analyzed using the Oak Ridge National Laboratory Isotope Generator (ORIGEN) Fallout Analysis Tool. An average photon energy of 0.81MeV is calculated and shown to be an accurate approximation of the fallout field energy distribution. A Gaussian distribution is used to calculate the minimal impact of …

Development Of Dose Conversion Coefficients For Radionuclides Produced In Spallation Neutron Sources, Phillip W. Patton

Transmutation Sciences Physics (TRP)

A research consortium comprised of representatives from several universities and national laboratories will be established as part of this project to generate internal and external dose conversion coefficients for radionuclides produced in spallation neutron sources. Information obtained from this multi-year study will be used to support the siting and licensing of future accelerator-driven nuclear initiatives within the U.S. Department of Energy complex, including the Spallation Neutron Source (SNS) and Accelerator Production of Tritium (APT) projects. Determination of these coefficients will also fill data gaps for several hundred radionuclides that exist in Federal Guidance Report (FGR) No. 11 and in Publications …

Symposium Participants' Bios, Bern Porter

Bern Porter Occasional Symposium Series

Biographical information about presenters and participants of the Bern Porter Occasional Symposium Series: The Bomb, the National Security State and the Advanced Thinking of Bern Porter.

Symposium Program, Bern Porter

Bern Porter Occasional Symposium Series

Printed program of the Bern Porter Occasional Symposium Series: The Bomb, the National Security State and the Advanced Thinking of Bern Porter.