Nuclear Commons^™

An Extension To Particle Polarizability To Predict Coupling Behavior In Periodic Nanoplasmonic Arrays, Drew Dejarnette

Graduate Theses and Dissertations

Plasmonic nanoparticles organized in arrays interact to create spectral patterns which are amplified by individual particle polarizability. It was hypothesized that particle polarizability could be used as a predictor of spectral behavior from far-field interactions within the array. Inter-particle coupling produced an extraordinary peak in extinction efficiency at wavelengths equal to or larger than the single particle plasmon resonance peak. Interactions that produced constructive coupling were found to mimic changes in the particle polarizability model. Testing of the hypothesis was performed using the coupled dipole approximation with parametric characterization of array geometries, giving specific particle size and lattice constant combinations …

Phase Control In Atomic Coherence, Utsab Khadka

Graduate Theses and Dissertations

In this thesis, atomic coherence is used to enhance nonlinear optical processes in multi-level atoms. The multi-photon transitions are driven resonantly, and at the same time without absorptive losses, by using electromagnetically induced transparency (EIT), thereby allowing the study of χ⁽³⁾ and χ⁽⁵⁾ nonlinearities using weak driving fields. The coherently modified probe beam(s) and the atom-radiated signal fields arising from four- and six- wave- mixing (FWM and SWM) processes are measured in the spectral, temporal and spatial domains.

In a three-level ladder-type atomic system, multiple peaks having spectral asymmetries are observed in the EIT window as well as …

Hrc Enews — 2012 Summer, 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.

Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E′Pp)N, H. Baghdasaryan, Gerard P. Gilfoyle, Et. Al.

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 ( …

Calibration Of A Silver Detector Using A Pube Source, Melanie E. Mace

Theses and Dissertations

During the initial design of the Field Reversed Compression and Heating Experiment (FRCHX), magnetohydrodynamic simulations performed by Los Alamos National Laboratory using MACH2 predicted a neutron yield on the order of 10¹² neutrons. However, Air Force Research Laboratory (AFRL) measurements indicate a total of 10⁷-10⁸ neutrons are generated from the FRCHX. A PuBe source was used to create a burst of neutrons to calibrate an AFRL silver detector based on distance to determine if the four order of magnitude discrepancy was cause by an improperly calibrated detector. It was determined that the calibration equation in use …

Measurement Of The Entry-Spin Distribution Imparted To The High Excitation Continuum Region Of Gadolinium Nuclei Via (P,D) And (P,T) Reactions, T. J. Ross, C. W. Beausang, R. O. Hughes, J. M. Allmond, C. Angell, M. S. Basunia, D. L. Bleuel, J. T. Burke, R. J. Casperson, J. Escher, P. Fallon, R. Hatarik, J. Munson, S. Paschalis, M. Petri, L. Phair, J. J. Ressler, N. D. Scielzo, I. Thompson

Physics Faculty Publications

Over the last several years, the surrogate reaction technique has been successfully employed to extract (n,f) and (n,γ) cross sections in the actinide region to a precision of ∼5% and ∼20%, respectively. However, attempts to apply the technique in the rare earth region have shown large (factors of 2–3) discrepancies between the directly measured (n,γ) and extracted surrogate cross sections. One possible origin of this discrepancy lies in differences between the initial spin-parity population distribution in the neutron induced and surrogate reactions. To address this issue, the angular …

Statistical Γ Rays In The Analysis Of Surrogate Nuclear Reactions, N. D. Scielzo, J. Escher, J. M. Allmond, M. S. Basunia, C. W. Beausang, L. A. Bernstein, D. L. Bleuel, J. T. Burke, R. M. Clark, F. S. Dietrich, P. Fallon, J. Gibelin, B. L. Goldblum, S. R. Lesher, M. A. Mcmahan, E. B. Norman, L. Phair, E. Rodriguez-Vieitez, S. A. Sheets, I. Thompson, M. Wiedeking

Physics Faculty Publications

The surrogate nuclear reaction method is being applied in many efforts to indirectly determine neutron-induced reaction cross sections on short-lived isotopes. This technique aims to extract accurate (n,γ) cross sections from measured decay properties of the compound nucleus of interest (created using a different reaction). The advantages and limitations of a method that identifies the γ-ray decay channel by detecting any high-energy (“statistical”) γ ray emitted during the relaxation of the compound nucleus were investigated. Data collected using the Silicon Telescope Array for Reaction Studies and Livermore-Berkeley Array for Collaborative Experiments silicon and germanium detector arrays were used …

Light Vs. Quantum Gravity, Irving Martinez^*

COURI Symposium Abstracts, Spring 2012

No abstract provided.

Measurement Of The Neutron F2 Structure Function Via Spectator Tagging With Clas, N. Baillie, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

We report on the first measurement of the F₂ structure function of the neutron from semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100° MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fⁿ₂ data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q² < 4.52 GeV², with uncertainties from nuclear corrections estimated to be less than …

Hrc Enews — 2012 Spring, 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.

Single And Double Spin Asymmetries For Pion Electro-Production From The Deuteron In The Resonance Region, Sharon L. Careccia

Physics Theses & Dissertations

The single and double spin asymmetries A_t and A_et have been measured in π^- electro-production off the deuteron using a longitudinally polarized electron beam and a polarized ND₃ target. The electron beam was polarized using a strained GaAs cathode and the target was polarized using Dynamic Nuclear Polarization. The data were collected at beam energies of 1.6, 1.7, 2.5 and 4.2 GeV in Hall B at Jefferson Lab in the spring of 2001. The final state particles were detected in the CEBAF Large Acceptance Spectrometer (CLAS). The d(e,e'π-p)p exclusive channel was identified using the missing mass …

Measurement Of The Neutron F2 Structure Function Via Spectator Tagging With Clas, N. Baillie, S. Tkachenko, J. Zhang, P. Bosted, S. Bültmann, M. E. Christy, H. Fenker, K. A. Griffioen, C. E. Keppel, S. E. Kuhn, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, G. Dodge, N. Guler, C. E. Hyde, A. Klein, A. Klimenko, L. B. Weinstein

Physics Faculty Publications

We report on the first measurement of the F₂ structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fⁿ₂ data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q² < 4.52 GeV², with uncertainties from nuclear corrections estimated to be less …

Positron Lifetime Modulation By Electric Field Induced Positronium Formation On A Gold Surface, Daniel J. Higgins

Theses and Dissertations

The purpose of this project is to study the lifetime and annihilation mode of positrons, the antimatter counterpart to electrons, and the formation rate of positronium on a gold surface modified by gold nanoparticles under the influence of radial electric fields measured using two independent systems. The positron annihilation photon pair/triplet spectroscopy system uses a sodium iodide ring detector segmented into six detection regions providing rough position sensitivity to measure the ratio of two to three photon positron annihilation events. An increased rate of three photon annihilation events and a decreased rate of two photon annihilation events are observed when …

Design And Characterization Of A Three-Dimensional Positron Annihilation Spectroscopy System Using A Low-Energy Positron Beam, Stephen M. Jimenez

Theses and Dissertations

Previous forays by AFIT into positron research have resulted in the development of a new positron annihilation spectroscopy (PAS) technique and the procurement of a low-energy positron beam system. The primary purpose of this research was to design and build a state-of-the-art PAS laboratory at AFIT capable to address a myriad of DoD solid-state and surface physics questions. The main objectives were to acquire and assemble utilities to operate a positron beam, assemble and configure an ultra-high vacuum (UHV) system for samples, design and build an interface with a magnetic field to propagate positrons onto samples, and create a new …

Durability Of Mwcnt Composites Under Electron And Neutron Irradiation, Quan-Hai T. Lu

Theses and Dissertations

Electromagnetic interference shielding effectiveness and conductive properties of carbon nanotube containing composites intended for use as satellite surface materials have been investigated following electron and neutron irradiation. The MWCNT composites were irradiated to fluence levels of 10¹⁶ electrons/cm² with 500 keV electrons. Increase in EMI-SE and conductivity was observed following electron irradiation in two of the samples. The sample with alternating layers of MWCNT and glass had a decrease in conductivity and an increase in EMI-SE post irradiation. This would suggest that the different layered configuration does play a role in the durability of the composite. Having multiple …

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 …

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

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