Degree Level

Acceleration of electrons using an inverse free electron laser auto- accelerator (open access)

Acceleration of electrons using an inverse free electron laser auto- accelerator

We present data from our study of a device known as the inverse free electron laser. First, numerical simulations were performed to optimize the design parameters for an experiment that accelerates electrons in the presence of an undulator by stimulated absorption of radiation. The Columbia free electron laser (FEL) was configured as an auto-accelerator (IFELA) system; high power (MW`s) FEL radiation at {approximately}1.65 mm is developed along the first section of an undulator inside a quasi-optical resonator. The electron beam then traverses a second section of undulator where a fraction of the electrons is accelerated by stimulated absorption of the 1.65 mm wavelength power developed in the first undulator section. The second undulator section has very low gain and does not generate power on its own. We have found that as much as 60% of the power generated in the first section can be absorbed in the second section, providing that the initial electron energy is chosen correctly with respect to the parameters chosen for the first and second undulators. An electron momentum spectrometer is used to monitor the distribution of electron energies as the electrons exit the IFELA. We have found; using our experimental parameters, that roughly 10% of …
Date: July 1, 1992
Creator: Wernick, I. K. & Marshall, T. C.
System: The UNT Digital Library
Actinide Production in the Reaction of Heavy Ions withCurium-248 (open access)

Actinide Production in the Reaction of Heavy Ions withCurium-248

Chemical experiments were performed to examine the usefulness of heavy ion transfer reactions in producing new, neutron-rich actinide nuclides. A general quasi-elastic to deep-inelastic mechanism is proposed, and the utility of this method as opposed to other methods (e.g. complete fusion) is discussed. The relative merits of various techniques of actinide target synthesis are discussed. A description is given of a target system designed to remove the large amounts of heat generated by the passage of a heavy ion beam through matter, thereby maximizing the beam intensity which can be safely used in an experiment. Also described is a general separation scheme for the actinide elements from protactinium (Z = 91) to mendelevium (Z = 101), and fast specific procedures for plutonium, americium and berkelium. The cross sections for the production of several nuclides from the bombardment of {sup 248}Cm with {sup 18}O, {sup 86}Kr and {sup 136}Xe projectiles at several energies near and below the Coulomb barrier were determined. The results are compared with yields from {sup 48}Ca and {sup 238}U bombardments of {sup 248}Cm. Simple extrapolation of the product yields into unknown regions of charge and mass indicates that the use of heavy ion transfer reactions to produce …
Date: July 1, 1983
Creator: Moody, K. J.
System: The UNT Digital Library
Alpha-Decay Studies in the Heavy Element Region (open access)

Alpha-Decay Studies in the Heavy Element Region

Thesis describing a research conducted to extend observations on nuclear energy levels and how they effect the nucleus itself, and an investigation on the gamma rays associated for the even-even isotopes and to obtain additional data for the oddmass neclei in the hope that more regularities will become apparent for that class of nuclides.
Date: July 3, 1956
Creator: Hummel, John Philip
System: The UNT Digital Library
Alpha-Decay Studies in the Heavy-Element Region (open access)

Alpha-Decay Studies in the Heavy-Element Region

Using primarily a 75-cm radius of curvature 60 deg symmetrical electromagnetic analyzer, a study of the complexity of the following alpha spectra was made: Es/sup 253/, Cf/sup 246/, Cm/sup 244/, Am/sup 243/, Pu/sup 236,242/, Pa/sup 231/ , Th/sup 227,230/, Ac/sup 225/, At/sup 209/ and Po/sup 206/. An investigation of the gamma rays associated with the following isotopes was also madei /sup 236/, and Pa/sup 231/. Decay schemes have been suggested for most of the isotopes included in this study. Those for the even-even isotopes were found to conform well with the previously existing systematics for that group of nuclides. Many of the decay features of the odd-mass isotopes seemed to conform well with presently expanding theories. (auth)
Date: July 1, 1956
Creator: Hummel, J. P.
System: The UNT Digital Library
Analysis of Current Distribution in Electrolytic Cells With Flowing Mercury Cathodes (open access)

Analysis of Current Distribution in Electrolytic Cells With Flowing Mercury Cathodes

An idealized model is postulated embodying the essential features of industrial caustic-chlorine cells with horizontal flowing-mercury cathodes. This model is examined in detail, and relations expressing the local anode potential, cathode potential, and ohmic potential drop in the electrolyte in terms of local current density and other parameters are established. These relations are combined to give a system of equations relating current density at any location along the cell to applied total potential and to operating conditions in the cell upstream of the point in question. Numerical solutions of these equations for several cases of cell operating conditions are carried out on a digital computing machine. The effects of changes in operating parameters upon average current density, individual electrode potentials, and current distribution are evaluated. (auth)
Date: July 19, 1960
Creator: Grens, E. A., II
System: The UNT Digital Library
Angular Distribution of Photopions From Hydrogen (open access)

Angular Distribution of Photopions From Hydrogen

ABS>An accurate measurement of the differential cross section for the photoproduction of positive pions was made at the Berkeley synchrotron, for photon energies of 280 and 290 Mev. The mesons were produced in a thin-walled liquid hydrogen target, and the meson detection apparatus utilized the characteristic pi -- mu decay of the meson. The measurements were done in two steps, from 0 to 50 deg with equipment specifically designed to reduce a very high positron background, and from 30 to 160 deg with equipment whose efficiency and solid angle could be accurately determined. The experimental results in the small-angle region definitely show the effects of ''photoelectric'' production of pions from the cloud surrounding the nucleon, which are characterized by an abrupt flattening of the cross section in the region forward of 40 deg (c. m.). The results are compared to the theory of photoproduction derived from the dispersion relations, and the sgreement is satisfactory within the limitations of the theory. (auth)
Date: July 1, 1958
Creator: Knapp, E. A.
System: The UNT Digital Library
Antiproton Structure Function in P-Pbar Diffractive Interactions at Sqrt(s) = 1.96 Tev (open access)

Antiproton Structure Function in P-Pbar Diffractive Interactions at Sqrt(s) = 1.96 Tev

None
Date: July 1, 2007
Creator: Malbouisson, Helena & U., /Rio de Janeiro State
System: The UNT Digital Library
Baryon stopping and charged particle production from lead-lead collisions at 158 GeV per nucleon (open access)

Baryon stopping and charged particle production from lead-lead collisions at 158 GeV per nucleon

Net proton (proton minus antiproton) and negative charge hadron spectra (h-) from central Pb+Pb collisions at 158 GeV per nucleon at the CERN Super Proton Synchrotron were measured and compared to spectra from central collisions of the lighter S+S system. Net baryon distributions were derived from those of net protons and net lambdas. Stopping, or rapidity shift with respect to the beam, of net protons and net baryons increase with system size. The mean transverse momentum &60;pT&62; of net protons also increase with system size. The h- rapidity density scales with the number of participant nucleons for nuclear collisions, where their &60;pT&62; is independent of system size. The &60;pT&62; dependence upon particle mass and system size is consistent with larger transverse flow velocity at midrapidity for central collisions of Pb+Pb compared to that of S+S.
Date: July 1, 1999
Creator: Toy, Milton Y.
System: The UNT Digital Library
BioAerosol Mass Spectrometry: Reagentless Detection of Individual Airborne Spores and Other Bioagent Particles Based on Laser Desorption/Ionization Mass Spectrometry (open access)

BioAerosol Mass Spectrometry: Reagentless Detection of Individual Airborne Spores and Other Bioagent Particles Based on Laser Desorption/Ionization Mass Spectrometry

Better devices are needed for the detection of aerosolized biological warfare agents. Advances in the ongoing development of one such device, the BioAerosol Mass Spectrometry (BAMS) system, are described here in detail. The system samples individual, micrometer-sized particles directly from the air and analyzes them in real-time without sample preparation or use of reagents. At the core of the BAMS system is a dual-polarity, single-particle mass spectrometer with a laser based desorption and ionization (DI) system. The mass spectra produced by early proof-of-concept instruments were highly variable and contained limited information to differentiate certain types of similar biological particles. The investigation of this variability and subsequent changes to the DI laser system are described. The modifications have reduced the observed variability and thereby increased the usable information content in the spectra. These improvements would have little value without software to analyze and identify the mass spectra. Important improvements have been made to the algorithms that initially processed and analyzed the data. Single particles can be identified with an impressive level of accuracy, but to obtain significant reductions in the overall false alarm rate of the BAMS instrument, alarm decisions must be made dynamically on the basis of multiple analyzed particles. …
Date: July 20, 2004
Creator: Steele, P T
System: The UNT Digital Library
Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy (open access)

Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy

NMR spectroscopy is ideal for studying weak interactions (formation enthalpy {le}20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*{sub 2}Yb, is ideal for this purpose. cis-P{sub 2}PtH{sub 2}complexes (P = phosphine) were used to produce slow-exchange Cp*{sub 2}YbL adducts for NMR study. Reversible formation of (P{sub 2}PtH){sub 2} complexes from cis-P{sub 2}PtH{sub 2} complexes were also studied, followed by interactions of Cp*{sub 2}Yb with phosphines, R{sub 3}PX complexes. A NMR study was done on the interactions of Cp*{sub 2}Yb with H{sub 2}, CH{sub 4}, Xe, CO, silanes, stannanes, C{sub 6}H{sub 6}, and toluene.
Date: July 1, 1995
Creator: Schwartz, D.J.
System: The UNT Digital Library
Calculations of the ground state energy and exchange integrals of crystalline $sup 3$He (open access)

Calculations of the ground state energy and exchange integrals of crystalline $sup 3$He

Thesis. The variational equation is derived and discussed using Jastrowtype wave functions, which are a product of pair wave functions, as the trail wave function. The various approximations used in simplifying the variational equations so as to obtain a form that is possible to solve numerically are discussed also. A Monte Carlo calculation is described using the wave function obtained. Exchange in /sup 3/He is discussed. (MHR)
Date: July 1, 1973
Creator: Lim, W L
System: The UNT Digital Library
Calibration of new flavor tagging algorithms using Bs oscillations (open access)

Calibration of new flavor tagging algorithms using Bs oscillations

Over the past decades the current theoretical description, the Standard Model of elementary particle physics, was solidified by many measurements as the basic theory describing fundamental particles and their interactions. It is extremely successful in explaining the high-precision data collected by experiments so far. The Standard Model includes several intrinsic parameters which have to be measured in experiments. Independent analyses of different physical processes can constrain those parameters. By combining those measurements physicists might be sensitive to physics beyond the Standard Model. If they are inconsistent it allows to get a hint on the theory that might supersede the Standard Model. The goal of the analysis presented in this thesis is to measure some of these parameters in the B{sub s} meson system. The B{sub s} meson, consisting of an anti-b and s quark, is not a pure mass eigenstate, thus allowing a B{sub s} meson to oscillate into its antiparticle via weak interacting processes. This is a general feature of any neutral meson. The history of meson mixing measurements is more then 50 years old. It was first observed in the kaon system. The oscillation in the B{sub d} system was measured very precisely by the B factories, whereas …
Date: July 1, 2007
Creator: Mack, Philipp
System: The UNT Digital Library
CARBON AND DEUTERIUM NUCLEAR MAGNETIC RESONANCE IN SOLIDS (open access)

CARBON AND DEUTERIUM NUCLEAR MAGNETIC RESONANCE IN SOLIDS

In Chapter I we present the results on a study of cross polarization dynamics, between protons and carbon-13 in adamantane, by the direct observation of the dilute, carbon-13, spins. These dynamics are an important consideration in the efficiency of proton enhancement double-resonance techniques and they also provide good experimental models for statistical theories of cross relaxation. In order to test these theories we present a comparison of the experimental and theoretical proton dipolar fluctuation correlation time {tau}{sub c}, which is experimentally 110 {+-} 15 {micro}sec and theoretically 122 {micro}sec for adamantane. These double resonance considerations provide the background for extensions to deuterium and double quantum effects discussed in Chapter II. In Chapter II an approach to high resolution nmr of deuterium in solids is described. The m = 1 {yields} -1 transition is excited by a double quantum process and the decay of coherence Q({tau}) is monitored. Fourier transformation yields a deuterium spectrum devoid of quadrupole splittings and broadening. If the deuterium nuclei are dilute and the protons are spin decoupled, the double-quantum spectrum is a high resolution one and yields information on the deuterium chemical shifts {Delta}{omega}. The relationship Q({tau}) {approx} cos 2{Delta}{omega}{tau} is checked and the technique is …
Date: July 1, 1976
Creator: Shattuck, Thomas Wayne
System: The UNT Digital Library
The Charge asymmetry in W bosons produced in p anti-p collisions at center of mass energy - 1.96 TeV (open access)

The Charge asymmetry in W bosons produced in p anti-p collisions at center of mass energy - 1.96 TeV

The primary mode of production of W{sup +} bosons in a p{bar p} collider is u + {bar d} {yields} W{sup +}. The u quark generally carries more momentum than the {bar d} and the resultant W{sup +} tends to be boosted in the proton direction. Similarly, W bosons are boosted in the anti-proton direction. This is observed as an asymmetry in the rapidity distributions of positive and negative W bosons. Measurement of this asymmetry serves as a probe of the momentum distribution of partons within the proton. These distributions are required as input to the calculation of every p{bar p} production cross section. This thesis presents the first measurement at D0 of the charge asymmetry of the W boson production cross section as measured in W {yields} ev decays in 0.3 fb{sup -1} of p{bar p} collisions collected with the D0 Detector. Theoretical predictions made using the CTEQ6.1M and MRST(2004) parton distribution functions are compared with the measurement.
Date: July 1, 2005
Creator: Torborg, Julie M. & U., /Notre Dame
System: The UNT Digital Library
Chemically modified polymeric resins for separation of cations, organic acids, and small polar moleculea by high performance liquid chromatography (open access)

Chemically modified polymeric resins for separation of cations, organic acids, and small polar moleculea by high performance liquid chromatography

This thesis is divided into 4 parts: a review, ion chromatography of metal cations on carboxylic resins, separation of hydrophilic organic acids and small polar compounds on macroporous resin columns, and use of eluent modifiers for liquid chromatographic separation of carboxylic acids using conductivity detection.
Date: July 1, 1993
Creator: Morris, J. B.
System: The UNT Digital Library
Chemically modified polymeric resins for solid-phase extraction and group separation prior to analysis by liquid or gas chromatography (open access)

Chemically modified polymeric resins for solid-phase extraction and group separation prior to analysis by liquid or gas chromatography

Polystyrene divinylbenzene was modified by acetyl, sulfonic acid, and quaternary ammonium groups. A resin functionalized with an acetyl group was impregnated in a PTFE membrane and used to extract and concentrate phenolic compounds from aqueous samples. The acetyl group created a surface easily wetted, making it an efficient adsorbent for polar compounds in water. The membrane stabilized the resin bed. Partially sulfonated high surface area resins are used to extract and group separate an aqueous mixture of neutral and basic organics; the bases are adsorbed electrostatically to the sulfonic acid groups, while the neutraons are adsorbed hydrophobically. A two-step elution is then used to separate the two fractions. A partially functionalized anion exchange resin is used to separate organic acids and phenols from neutrals in a similar way. Carboxylic acids are analyzed by HPLC and phenols by GC.
Date: July 1, 1993
Creator: Schmidt, L. W.
System: The UNT Digital Library
Coherence in multilevel systems (open access)

Coherence in multilevel systems

Mathematical descriptions of an excited state multilevel system are developed to include progressively the effects of coherent coupling, feeding, decay and relaxation, and the expressions are illustrated with several pulse coherence experiments utilizing zero field optically detected magnetic resonance of excited triplet states. A new method is described in which the time development of the coherent components in a multilevel system is monitored by using an observable that can measure only relative populations between the levels. The method is illustrated. By treating a coherently driven excited state system as two levels in contact with a population reservoir, exact expressions are obtained for both transient and steady-state behavior in the presence of transverse and spin lattice relaxation, constant incoherent pumping, spontaneous emission between the two levels, and also decay back into the reservoir. The general mathematical development is applied specifically to zero field microwave phosphorescence double resonance. Experimental methods and apparatus are discussed in detail and results of optically detected transient mutations, spin echoes, and Fourier transform spectroscopy are presented. (26 figs, 220 refs) (auth)
Date: July 1, 1975
Creator: Breiland, W.G.
System: The UNT Digital Library
Cold Fusion Production and Decay of Neutron-Deficient Isotopes of Dubnium and Development of Extraction Systems for Group V Elements (open access)

Cold Fusion Production and Decay of Neutron-Deficient Isotopes of Dubnium and Development of Extraction Systems for Group V Elements

Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1730/1370 pb at an excitation energy of 16.0 +- 1.6 MeV. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier. The extraction of niobium (Nb) and tantalum (Ta) from hydrochloric acid and mixed hydrochloric acid/lithium chloride media by bis(2-ethylhexyl) hydrogen phosphate (HDEHP) and bis(2-ethylhexyl) hydrogen phosphite (BEHP) was studied. The goal of the experiments was to find a system that demonstrates selectivity among the members of group five of the Periodic Table and is also suitable for the study of dubnium (Db, Z = 105). Experiments with niobium and tantalum were performed with carrier (10-6 M), carrier free (10-10 M) and trace (10-16 M) concentrations of metal using hydrochloric acid solution with concentrations ranging from 1 - 11 …
Date: July 31, 2008
Creator: Gates, Jacklyn M.
System: The UNT Digital Library
A combined muon-neutrino and electron-neutrino oscillation search at MiniBooNE (open access)

A combined muon-neutrino and electron-neutrino oscillation search at MiniBooNE

MiniBooNE seeks to corroborate or refute the unconfirmed oscillation result from the LSND experiment. If correct, the result implies that a new kind of massive neutrino, with no weak interactions, participates in neutrino oscillations. MiniBooNE searches for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations with the Fermi National Accelerator Laboratory 8 GeV beam line, which produces a {nu}{sub {mu}} beam with an average energy of {approx} 0.8 GeV and an intrinsic {nu}{sub e} content of 0.4%. The neutrino detector is a 6.1 m radius sphere filled with CH{sub 2}, viewed by 1540 photo-multiplier tubes, and located 541 m downstream from the source. This work focuses on the estimation of systematic errors associated with the neutrino flux and neutrino interaction cross section predictions, and in particular, on constraining these uncertainties using in-situ MiniBooNE {nu}{sub {mu}} charged current quasielastic (CCQE) scattering data. A data set with {approx} 100,000 events is identified, with 91% CCQE purity. This data set is used to measure several parameters of the CCQE cross section: the axial mass, the Fermi momentum, the binding energy, and the functional dependence of the axial form factor on four-momentum transfer squared. Constraints on the {nu}{sub {mu}} and {nu}{sub e} fluxes are derived using …
Date: July 1, 2006
Creator: Monroe, Jocelyn R.
System: The UNT Digital Library
Computer modeling on neutron radiography (open access)

Computer modeling on neutron radiography

This report neutron radiography measuring methods and the neutron radiography model.
Date: July 1993
Creator: Groth, Troy
System: The UNT Digital Library
The Concept of Sets Enchained by a Stochastic Process and Its Use in Cascade Shower Theory (open access)

The Concept of Sets Enchained by a Stochastic Process and Its Use in Cascade Shower Theory

From abstract: "In the present paper, the above methodology is investigated stochastic processes in general and it is shown how certain choices of sets can be made which preserve the linearity properties, though not necessarily the Markovian principles"
Date: July 1954
Creator: Rankin, Bayard, 1924-
System: The UNT Digital Library
Current-potential characteristics of electrochemical systems (open access)

Current-potential characteristics of electrochemical systems

This dissertation contains investigations in three distinct areas. Chapters 1 and 2 provide an analysis of the effects of electromagnetic phenomena during the initial stages of cell discharge. Chapter 1 includes the solution to Maxwell`s equations for the penetration of the axial component of an electric field into an infinitely long cylindrical conductor. Chapter 2 contains the analysis of the conductor included in a radial circuit. Chapter 3 provides a complete description of the equations that describe the growth of an oxide film. A finite difference program was written to solve the equations. The system investigated is the iron/iron oxide in a basic, aqueous solution. Chapters 4 and 5 include the experimental attempts for replacing formaldehyde with an innocuous reducing agent for electroless deposition. In chapter 4, current-versus-voltage curves are provided for a sodium thiosulfate bath in the presence of a copper disk electrode. Also provided are the cathodic polarization curves of a copper/EDTA bath in the presence of a copper electrode. Chapter 5 contains the experimental results of work done with sodium hypophosphite as a reducing agent. Mixed-potential-versus-time curves for solutions containing various combinations of copper sulfate, nickel chloride, and hypophosphite in the presence of a palladium disk electrode …
Date: July 1, 1993
Creator: Battaglia, V. S.
System: The UNT Digital Library
Dalitz Analysis of D0 to K0(S) Pi+ Pi- and Measurement of the CKM Angle Gamma in Charged B+- Decays to D(*) K+- Decays (open access)

Dalitz Analysis of D0 to K0(S) Pi+ Pi- and Measurement of the CKM Angle Gamma in Charged B+- Decays to D(*) K+- Decays

Despite more than thirty years having elapsed since the discovery of CP violation, our understanding about the source and the nature of this phenomenon is still very limited. In the standard model of particle physics, CP violation is due to the presence of an non-irreducible weak phase in the Cabibbo-Kabayashi-Maskawa(CKM) matrix. Up to now, all the experimental results are in good agreement with the standard model. However, it is important for us to over-constrain the CKM quark-mixing matrix and explore the possibility of new physics beyond the standard model. The B meson provides an ideal place to measure CP violation due to its heavy mass and potentially large CP-violating effects. In particular, the angle {gamma} of the Unitary Triangle relating the elements of the CKM matrix is extremely crucial in terms of CP violation and constraints on the new physics models. Various methods using B{sup -} {yields} D{sup 0}K{sup -} decays have been proposed to measure based on the interference between the V{sub cb} and V{sub ub} amplitudes. Despite the simple concept, the measurement turns out to be experimentally challenging due to the small branching fraction and the small value of {tau}{sub B}, the amplitude ratio between the two contributing …
Date: July 10, 2007
Creator: Lau, Yan-Pan
System: The UNT Digital Library
Decay Schemes of Odd-Odd Einsteinium Isotopes (open access)

Decay Schemes of Odd-Odd Einsteinium Isotopes

None
Date: July 1, 1965
Creator: McHarris, W. C.
System: The UNT Digital Library