Fall and winter movements and activity of muskrats in east-central Minnesota (open access)

Fall and winter movements and activity of muskrats in east-central Minnesota

None
Date: August 1, 1974
Creator: Stolen, Paul Dean
System: The UNT Digital Library
The Specific Heat of Dysprosium Metal Between 0.4 and 4 K (open access)

The Specific Heat of Dysprosium Metal Between 0.4 and 4 K

Submitted to Illinois Inst. of Tech., Chicago. A He/sup 3/ cryostat was built to measure the specific heat of rare earth metals which have a component, at low temperatures, attributable to the electrons in the incomplete 4f shell. The specific heat of dysprosium from 0.4 to 4.2 deg K was measured. Pertinent theories about specific heats are outlined. The apparatus included the cryostat, vacuum and He/sup 3/ systems, calorimeter, carbon thermometer, heater, and magnetic thermometer. The experimental procedure is described and results are presented in graphic and tabular form. The specific heat rose sharply below 1 deg K. An anomalous hump was centered about 2.35 deg K. (M.C.G.)
Date: August 1, 1962
Creator: Guenther, R. A.
System: The UNT Digital Library
Response of Shortgrass Plains Vegetation to Chronic and Seasonally Administered Gamma Radiation (open access)

Response of Shortgrass Plains Vegetation to Chronic and Seasonally Administered Gamma Radiation

In order to determine the effect of radiation on the structure of native shortgrass plains vegetation, an 8750 Ci 137Cs source was installed on the Central Plains Experimental Range near Nunn, Colorado; The experimental area was divided into 6 treatment sectors, a control, 2 sectors for chronic exposure (irradiation initiated April 1969 and continuing as of August 1971), and one each for spring, summer and late fall seasonal semi-acute (30 day), exposures which were administered during April, July and December, 1969, respectively. Community structure was measured by coefficient of community and diversity index. Yield was determined by clipping plots in September 1970 and visual estimates in September 1969 and 1970 for the grass-sedge component of the vegetation. Individual species sensitivity was determined by density data recorded in April, June and September of 1969 and 1970 and by a phenological index recorded at weekly intervals during the 1969 and 1970 growing seasons. The response of the vegetation was similar whether determined by coefficient of community or diversity with diversity being a more sensitive measure of effects. In the chronically exposed sectors, the exposure rate which resulted in a 50 per cent reduction in these 2 parameters (CC50 or D50) was still …
Date: August 1, 1971
Creator: Fraley, L. Jr.
System: The UNT Digital Library
A Method for Estimating the Heat of Formation and Free Energy of Formation of Inorganic Compounds (open access)

A Method for Estimating the Heat of Formation and Free Energy of Formation of Inorganic Compounds

None
Date: August 1, 1962
Creator: Wilcox, D. E.
System: The UNT Digital Library
Search for new physics in the Compact Muon Solenoid (CMS) experiment and the response of the CMS calorimeters to particles and jets (open access)

Search for new physics in the Compact Muon Solenoid (CMS) experiment and the response of the CMS calorimeters to particles and jets

A Monte Carlo study of a generic search for new resonances beyond the Standard Model (SM) in the CMS experiment is presented. The resonances are axigluon, coloron, E{sub 6} diquark, excited quark, W{prime}, Z{prime}, and the Randall-Sundrum graviton which decay to dijets. The dijet resonance cross section that the CMS can expect to discover at a 5{sigma} significance or to exclude at 95% confidence level for integrated luminosities of 100 pb{sup -1}, 1 fb{sup -1}, and 10 fb{sup -1} is evaluated. It is shown that a 5{sigma} discovery of a multi-TeV dijet resonance is possible for an axigluon, excited quark, and E{sub 6} diquark. However, a 5{sigma} discovery can not be projected with confidence for a W{prime}, Z{prime} and the Randall-Sundrum graviton. On the other hand, 95% CL exclusion mass regions can be measured for all resonances at high luminosities. In the second part of this dissertation, the analyses of the 2006 test beam data from the combined electromagnetic and hadronic barrel calorimeters are presented. The CMS barrel calorimeters response to a variety of beam particles in a wide momenta range (1 to 350 GeV/c) is measured. Furthermore, using these beam data, the expected performance of the barrel calorimeters to …
Date: August 1, 2008
Creator: Gumus, Kazim Ziya & Tech., /Texas
System: The UNT Digital Library
Type Ia supernova rate studies from the SDSS-II Supernova Study (open access)

Type Ia supernova rate studies from the SDSS-II Supernova Study

The author presents new measurements of the type Ia SN rate from the SDSS-II Supernova Survey. The SDSS-II Supernova Survey was carried out during the Fall months (Sept.-Nov.) of 2005-2007 and discovered {approx} 500 spectroscopically confirmed SNe Ia with densely sampled (once every {approx} 4 days), multi-color light curves. Additionally, the SDSS-II Supernova Survey has discovered several hundred SNe Ia candidates with well-measured light curves, but without spectroscopic confirmation of type. This total, achieved in 9 months of observing, represents {approx} 15-20% of the total SNe Ia discovered worldwide since 1885. The author describes some technical details of the SN Survey observations and SN search algorithms that contributed to the extremely high-yield of discovered SNe and that are important as context for the SDSS-II Supernova Survey SN Ia rate measurements.
Date: August 1, 2008
Creator: Dilday, Benjamin
System: The UNT Digital Library
QCD fits to neutrino-iron structure functions at NuTeV (open access)

QCD fits to neutrino-iron structure functions at NuTeV

This thesis presents a new determination of {Lambda}{sub QCD} from Next-to-Leading Order QCD fits to the Q{sup 2} dependence of neutrino-iron structure functions. This is the first measurement of {Lambda}{sub QCD} which uses a theoretical model that fully accounts for heavy quark production. Compared with previous neutrino measurements, the result has improved understanding of the largest systematic uncertainties on the muon and hadron energy scales. These improvements lead to one of the most precise determination of {alpha}{sub S} at moderate Q{sup 2}. NuTeV is a neutrino-iron deep inelastic scattering (DIS) experiment that collected data during 1996-97 at Fermilab. The key features of NuTeV include its sign-selected beam which produced separate high purity neutrino and antineutrino beams, and its continuous calibration beam which enabled NuTeV to considerably improve the knowledge of energy scales which have dominated uncertainties in the previous measurements.
Date: August 1, 2006
Creator: Radescu, Voica A. & U., /Pittsburgh
System: The UNT Digital Library
Error-Induced Beam Degradation in Fermilab's Accelerators (open access)

Error-Induced Beam Degradation in Fermilab's Accelerators

In Part I, three independent models of Fermilab's Booster synchrotron are presented. All three models are constructed to investigate and explore the effects of unavoidable machine errors on a proton beam under the influence of space-charge effects. The first is a stochastic noise model. Electric current fluctuations arising from power supplies are ubiquitous and unavoidable and are a source of instabilities in accelerators of all types. A new noise module for generating the Ornstein-Uhlenbeck (O-U) stochastic noise is first created and incorporated into the existing Object-oriented Ring Beam Injection and Tracking (ORBIT-FNAL) package. After being convinced with a preliminary model that the noise, particularly non-white noise, does matter to beam quality, we proceeded to measure directly current ripples and common-mode voltages from all four Gradient Magnet Power Supplies (GMPS). Then, the current signals are Fourier-analyzed. Based upon the power spectra of current signals, we tune up the Ornstein-Uhlnbeck noise model. As a result, we are able to closely match the frequency spectra between current measurements and the modeled O-U stochastic noise. The stochastic noise modeled upon measurements is applied to the Booster beam in the presence of the full space-charge effects. This noise model, accompanied by a suite of beam …
Date: August 1, 2007
Creator: Yoon, Phil S.
System: The UNT Digital Library
Measurement of the W boson helicity in top quark decays (open access)

Measurement of the W boson helicity in top quark decays

A measurement of the fraction, f{sup +}, of right-handed W bosons produced in top quark decays is presented. This analysis is based on a sample corresponding to an integrated luminosity of 370 pb{sup -1}, collected by the D0 detector at the Fermilab Tevatron p{bar p} Collider at {radical}s = 1.96 TeV. The helicity angle, {theta}*, is reconstructed for each lepton. f{sup +} is determined by comparing the cos {theta}* distribution from the data with that for the expected background and signal for various values of f{sup +}. The fraction of longitudinal W bosons, f{sup 0}, is assumed to be 0.7 as predicted by the standard model. This yields f{sup +} = 0.109 {+-} 0.094 (stat) {+-} 0.063 (syst), consistent with the standard model prediction of f{sup +} = 3.6x 10{sup -4}. The possibility that both f{sup +} and f{sup 0} stray from standard model values is also investigated. In this case cos {theta}* distributions for each possible W helicity state, along with the backgrounds, are fit to the cos {theta}* distribution for the data. The best fit values are f{sup +} = 0.82 {+-} 0.30(stat) and f{sup 0} = -0.58 {+-} 0.50(stat).
Date: August 1, 2007
Creator: Gmyrek, Bryan David
System: The UNT Digital Library
Search for Higgs bosons decaying into tau pairs in ppbar collisions at D0 (open access)

Search for Higgs bosons decaying into tau pairs in ppbar collisions at D0

A search for neutral Higgs bosons decaying into tau pairs is presented using data in p{bar p} collisions at {radical}s = 1.96 TeV. One of the tau leptons is identified via its decay into an electron or muon and the other via its decay into a hadronic final state. The data, corresponding to an integrated luminosity of around 1.0 fb{sup -1}, were collected with the D0 detector at the Fermilab Tevatron collider between April 2002 and February 2006. No significant excess of events above the background expectation is observed and limits on the cross section times branching ratio for neutral Higgs bosons decaying into tau pairs, p{bar p} {yields} {phi} {yields} {tau}{sup +}{tau}{sup -}, are set. The cross section limits are interpreted as exclusions in the parameter space of the minimal supersymmetric Standard Model, resulting in exclusions in the range 40 < tan{beta} < 70 for M{sub A} < 200 GeV. Finally, the effect of Higgs bosons with a large total width is considered and the first model independent correction to the cross section limits for the width effect is presented.
Date: August 1, 2008
Creator: Owen, Mark A.
System: The UNT Digital Library
Evidence for single top quark production using Bayesian neural networks (open access)

Evidence for single top quark production using Bayesian neural networks

We present results of a search for single top quark production in p{bar p} collisions using a dataset of approximately 1 fb{sup -1} collected with the D0 detector. This analysis considers the muon+jets and electron+jets final states and makes use of Bayesian neural networks to separate the expected signals from backgrounds. The observed excess is associated with a p-value of 0.081%, assuming the background-only hypothesis, which corresponds to an excess over background of 3.2 standard deviations for a Gaussian density. The p-value computed using the SM signal cross section of 2.9 pb is 1.6%, corresponding to an expected significance of 2.2 standard deviations. Assuming the observed excess is due to single top production, we measure a single top quark production cross section of {sigma}(p{bar p} {yields} tb + X, tqb + X) = 4.4 {+-} 1.5 pb.
Date: August 1, 2007
Creator: Kau, Daekwang
System: The UNT Digital Library
Design of a boron neutron capture enhanced fast neutron therapy assembly (open access)

Design of a boron neutron capture enhanced fast neutron therapy assembly

The use of boron neutron capture to boost tumor dose in fast neutron therapy has been investigated at several fast neutron therapy centers worldwide. This treatment is termed boron neutron capture enhanced fast neutron therapy (BNCEFNT). It is a combination of boron neutron capture therapy (BNCT) and fast neutron therapy (FNT). It is believed that BNCEFNT may be useful in the treatment of some radioresistant brain tumors, such as glioblastoma multiform (GBM). A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses a tungsten filter and collimator near the patient's head, with a graphite reflector surrounding the head to significantly increase the dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code MCNP version 5 for a standard 20x20 cm{sup 2} treatment beam. The calculated boron dose enhancement at 5.7-cm depth in a water-filled head phantom in the assembly with a 5x5 cm{sup 2} collimation was 21.9% per 100-ppm {sup 10}B for a 5.0-cm tungsten filter and 29.8% for a 8.5-cm tungsten filter. The corresponding dose rate for the 5.0-cm and 8.5-cm thick filters were 0.221 and 0.127 Gy/min, respectively; about …
Date: August 1, 2006
Creator: Wang, Zhonglu & Tech, /Georgia
System: The UNT Digital Library
A Measurement of the Top Quark Mass in the Dilepton Decay Channel at CDF II (open access)

A Measurement of the Top Quark Mass in the Dilepton Decay Channel at CDF II

The top quark, the most recently discovered quark, is the most massive known fundamental fermion. Precision measurements of its mass, a free parameter in the Standard Model of particle physics, can be used to constrain the mass of the Higgs Boson. In addition, deviations in the mass as measured in different channels can provide possible evidence for new physics. We describe a measurement of the top quark mass in the decay channel with two charged leptons, known as the dilepton channel, using data collected by the CDF II detector from p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convolving the leading order matrix element describing q{bar q} {yields} t{bar t} {yields} b{ell}{nu}{sub {ell}}{bar b}{ell}'{nu}{sub {ell}'} with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 1.0 fb{sup -1}, we observe 78 candidate events and measure M{sub t} = 164.5 {+-} 3.9(stat.) {+-} 3.9(syst.) GeV/c{sup 2}, the most precise measurement of the top quark mass in this channel to date.
Date: August 1, 2006
Creator: Jayatilaka, Bodhitha A.
System: The UNT Digital Library
Study of the Rare Decay K(L) ---> pi0 gamma gamma at KTeV (open access)

Study of the Rare Decay K(L) ---> pi0 gamma gamma at KTeV

The authors study on the rare decay K{sub L} {yields} {pi}{sup 0}{gamma}{gamma}, measure a{sub V}, and branching ratio by analyzing 96, 97 and 99 data. The measurements were taken by KTeV at Fermi National Accelerator Laboratory. After all cuts, they have 1982 K{sub L} {yields} {pi}{sup 0}{gamma}{gamma} candidate. The background level is estimated as 30%. K{sub L} {yields} {pi}{sup 0}{gamma}{gamma} branching ratio is measured as (1.29 {+-} 0.03(stat) {+-} 0.04(sys)) x 10{sup -6}. By using D'Ambrosio's theory to fit a{sub V}, a{sub V} = -(-0.31 {+-} 0.05(stat) {+-} 0.07(sys)).
Date: August 1, 2007
Creator: Wang, Jianbo
System: The UNT Digital Library
Diagnostics of the Fermilab Tevatron using an AC dipole (open access)

Diagnostics of the Fermilab Tevatron using an AC dipole

The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f {approx} 20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of the beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of …
Date: August 1, 2008
Creator: Miyamoto, Ryoichi
System: The UNT Digital Library
Search for Single Top Quark Production with the CDF Run II Detector Using a Multivariate Likelihood Method (open access)

Search for Single Top Quark Production with the CDF Run II Detector Using a Multivariate Likelihood Method

None
Date: August 1, 2008
Creator: Budd, Sarah Rebecca
System: The UNT Digital Library
A Measurement of the Branching Ratio of the pi0 Dalitz Decay using K(L) ---> 3 pi0 Decays from KTeV (open access)

A Measurement of the Branching Ratio of the pi0 Dalitz Decay using K(L) ---> 3 pi0 Decays from KTeV

The authors present a measurement of B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma})/B({pi}{sup 0} {yields} {gamma}{gamma}) using data taken in 1999 by the E832 KTeV experiment at Fermilab. The {pi}{sup 0}s were produced by K{sub L} decays in flight that are fully reconstructed. They find 63,693 K{sub L} {yields} 3{pi}{sup 0} {yields} {gamma}{gamma} {gamma}{gamma} e{sup +}e{sup -}{gamma} decays in KTeV data (an increase of a factor of {approx} 20 in event statistics over previous experiments), and normalize to K{sub L} {yields} 3{pi}{sup 0} {yields} 6{gamma}, to extract B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma}, m{sub e{sup +}e{sup -}} > 15 MeV/c{sup 2})/B({pi}{sup 0} {yields} {gamma}{gamma}) = (3.920 {+-} 0.016 {+-} 0.036) x 10{sup -3}, where the first error is statistical and the second is systematic. Using the Mikaelian and Smith prediction for the e{sup +}e{sup -} mass spectrum as implemented in the KTeV Monte Carlo to correct to the full e{sup +}e{sup -} mass range yields B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma})/B({pi}{sup 0} {yields} {gamma}{gamma}) = (1.1559 {+-} 0.0046 {+-} 0.0107)%. This result is consistent with previous measurements and with theoretical predictions, and the uncertainty is a factor of three smaller than any previous measurement.
Date: August 1, 2007
Creator: Abouzaid, Erin E.
System: The UNT Digital Library
Measurement of Branching Ratios for Non-leptonic Cabibbo-suppressed Decays of the Charmed-Strange Baryon Xic+ (open access)

Measurement of Branching Ratios for Non-leptonic Cabibbo-suppressed Decays of the Charmed-Strange Baryon Xic+

We studied several {Xi}{sub c}{sup +} decay modes, most of them with a hyperon in the final state, and determined their branching ratios. The data used in this analysis come from the fixed target experiment SELEX, a multi-stage spectrometer with high acceptance for forward interactions, that took data during 1996 and 1997 at Fermilab with 600 GeV=c (mainly {Sigma}{sup -}, {pi}{sup -}) and 540 GeV/c (mainly p) beams incident on copper and carbon targets. The thesis mainly details the first observation of two Cabibbo-suppressed decay modes, {Xi}{sub c}{sup +} {yields} {Sigma}{sup +}{pi}{sup -}{pi}{sup +} and {Xi}{sub c}{sup +} {yields} {Sigma}{sup -}{pi}{sup +}{pi}{sup +}. The branching ratios of the decays relative to the Cabibbo-favored {Xi}{sub c}{sup +} {yields} {Xi}{sup -}{pi}{sup +}{pi}{sup +} are measured to be: {Lambda}({Xi}{sub c}{sup +} {yields} {Sigma}{sup -}{pi}{sup +}{pi}{sup +})/{Lambda}({Xi}{sub c}{sup +} {yields} {Xi}{sup -}{pi}{sup +}{pi}{sup +}) = 0.184 {+-} 0.086. Systematic studies have been performed in order to check the stability of the measurements varying all cuts used in the selection of events over a wide interval and we do not observe evidence of any trend, so the systematic error is negligible in the final results because the quadrature sum of the total error is not …
Date: August 1, 2008
Creator: Vazquez Jauregui, Eric & U., /San Luis Potosi
System: The UNT Digital Library
Flow cytometric analysis of mitotic cycle perturbation by chemical carcinogens in cultured epithelial cells. [Effects of benzo(a)pyrene-diol-epoxide on mitotic cycle of cultural mouse liver epithelial cells] (open access)

Flow cytometric analysis of mitotic cycle perturbation by chemical carcinogens in cultured epithelial cells. [Effects of benzo(a)pyrene-diol-epoxide on mitotic cycle of cultural mouse liver epithelial cells]

A system for kinetic analysis of mitotic cycle perturbation by various agents was developed and applied to the study of the mitotic cycle effects and dependency of the chemical carcinogen benzo(a)pyrene-diolepoxide, DE, upon a mouse lever epithelial cell line, NMuLi. The study suggests that the targets of DE action are not confined to DNA alone but may include cytoplasmic structures as well. DE was found to affect cells located in virtually every phase of the mitotic cycle, with cells that were actively synthesizing DNA showing the strongest response. However, the resulting perturbations were not confined to S-phase alone. DE slowed traversal through S-phase by about 40% regardless of the cycle phase of the cells exposed to it, and slowed traversal through G/sub 2/M by about 50%. When added to G/sub 1/ cells, DE delayed recruitment of apparently quiescent (G/sub 0/) cells by 2 hours, and reduced the synchrony of the cohort of cells recruited into active proliferation. The kinetic analysis system consists of four elements: tissue culture methods for propagating and harvesting cell populations; an elutriation centrifugation system for bulk synchronization of cells in various phases of the mitotic cycle; a flow cytometer (FCM), coupled with appropriate staining protocols, to …
Date: August 1, 1978
Creator: Pearlman, A.L.
System: The UNT Digital Library
Determination of the strong coupling constant ({alpha}{sub s}) and a test of perturbative QCD using W + jets processes in the D0 detector (open access)

Determination of the strong coupling constant ({alpha}{sub s}) and a test of perturbative QCD using W + jets processes in the D0 detector

The D0 experiment has accumulated data for a study of inclusive W production corresponding to a total integrated luminosity of 14.3 {plus_minus} 1.7 pb{sup {minus}1} during the 1992--1993 Fermilab Tevatron collider run. The total number of W {yields} e + {nu} candidates is 9770. The ratio of the number of W + 1 jet events to that of W + 0 jet events has been measured as a function of jet minimum E{sub T}. Using this ratio the strong coupling constant, {alpha}{sub s} at Q{sup 2} = M{sub W}{sup 2} is measured to be {alpha}{sub s}(M{sub W}{sup 2}) = 0.124 {plus_minus} 0.005(stat) {plus_minus} 0.006(MC) {plus_minus} 0.008(theory){sub {minus}0.022}{sup +0.026}(sys) or ({sub {minus}0.025}{sup +0.028} combined) with a jet minimum E{sub T} of 25 GeV. A quantitative test of perturbative QCD has been made by comparing the experimentally measured ratio with the theoretical predictions. The theoretical predictions of the ratio in both the leading order and next-to-leading order are in good agreement with the measured ratio.
Date: August 1, 1993
Creator: Yu, Jaehoon
System: The UNT Digital Library
Structural studies of polypeptides: Mechanism of immunoglobin catalysis and helix propagation in hybrid sequence, disulfide containing peptides (open access)

Structural studies of polypeptides: Mechanism of immunoglobin catalysis and helix propagation in hybrid sequence, disulfide containing peptides

Catalytic immunoglobin fragments were studied Nuclear Magnetic Resonance spectroscopy to identify amino acid residues responsible for the catalytic activity. Small, hybrid sequence peptides were analyzed for helix propagation following covalent initiation and for activity related to the protein from which the helical sequence was derived. Hydrolysis of p-nitrophenyl carbonates and esters by specific immunoglobins is thought to involve charge complementarity. The pK of the transition state analog P-nitrophenyl phosphate bound to the immunoglobin fragment was determined by {sup 31}P-NMR to verify the juxtaposition of a positively charged amino acid to the binding/catalytic site. Optical studies of immunoglobin mediated photoreversal of cis, syn cyclobutane thymine dimers implicated tryptophan as the photosensitizing chromophore. Research shows the chemical environment of a single tryptophan residue is altered upon binding of the thymine dimer. This tryptophan residue was localized to within 20 {Angstrom} of the binding site through the use of a nitroxide paramagnetic species covalently attached to the thymine dimer. A hybrid sequence peptide was synthesized based on the bee venom peptide apamin in which the helical residues of apamin were replaced with those from the recognition helix of the bacteriophage 434 repressor protein. Oxidation of the disufide bonds occured uniformly in the proper …
Date: August 1, 1992
Creator: Storrs, R. W.
System: The UNT Digital Library
Measurement of current density fluctuations and ambipolar particle flux due to magnetic fluctuations in MST (open access)

Measurement of current density fluctuations and ambipolar particle flux due to magnetic fluctuations in MST

Studies of magnetic fluctuation induced particle transport on Reversed Field Pinch plasmas were done on the Madison Symmetric Torus. Plasma current density and current density fluctuations were measured using a multi-coil magnetic probes. The low frequency (f<50 kHz) current density fluctuations are consistent with the global resistive tearing instabilities predicted by 3-D MHD simulations. At frequencies above 50 kHz, the magnetic fluctuations were detected to be localized with a radial correlation length of about 1--2 cm. These modes are locally resonant modes since the measured dominant mode number spectra match the local safety factor q. The net charged particle flux induced by magnetic fluctuations was obtained by measuring the correlation term <{tilde j}{sub {parallel}} {tilde B}{sub r}>. The result of zero net charged particle loss was obtained, meaning the flux is ambipolar. The ambipolarity of low frequency global tearing modes is satisfied through the phase relations determined by tearing instabilities. The ambipolarity of high frequency localized modes could be partially explained by the simple model of Waltz based on the radial average of small scale turbulence.
Date: August 1, 1992
Creator: Shen, Weimin
System: The UNT Digital Library
Development and application of a high speed digital data acquisition technique to study steam bubble collapse using particle image velocimetry (open access)

Development and application of a high speed digital data acquisition technique to study steam bubble collapse using particle image velocimetry

The use of a Particle Image Velocimetry (PIV) method, which uses digital cameras for data acquisition, for studying high speed fluid flows is usually limited by the digital camera`s frame acquisition rate. The velocity of the fluid under study has to be limited to insure that the tracer seeds suspended in the fluid remain in the camera`s focal plane for at least two consecutive images. However, the use of digital cameras for data acquisition is desirable to simplify and expedite the data analysis process. A technique was developed which will measure fluid velocities with PIV techniques using two successive digital images and two different framing rates simultaneously. The first part of the method will measure changes which occur to the flow field at the relatively slow framing rate of 53.8 ms. The second part will measure changes to the same flow field at the relatively fast framing rate of 100 to 320 {mu}s. The effectiveness of this technique was tested by studying the collapse of steam bubbles in a subcooled tank of water, a relatively high speed phenomena. The tracer particles were recorded and velocity vectors for the fluid were obtained far from the steam bubble collapse.
Date: August 1, 1992
Creator: Schmidl, W. D.
System: The UNT Digital Library
Zone Refining of Plutonium Metal (open access)

Zone Refining of Plutonium Metal

The zone refining process was applied to Pu metal containing known amounts of impurities. Rod specimens of plutonium metal were melted into and contained in tantalum boats, each of which was passed horizontally through a three-turn, high-frequency coil in such a manner as to cause a narrow molten zone to pass through the Pu metal rod 10 times. The impurity elements Co, Cr, Fe, Ni, Np, U were found to move in the same direction as the molten zone as predicted by binary phase diagrams. The elements Al, Am, and Ga moved in the opposite direction of the molten zone as predicted by binary phase diagrams. As the impurity alloy was zone refined, {delta}-phase plutonium metal crystals were produced. The first few zone refining passes were more effective than each later pass because an oxide layer formed on the rod surface. There was no clear evidence of better impurity movement at the slower zone refining speed. Also, constant or variable coil power appeared to have no effect on impurity movement during a single run (10 passes). This experiment was the first step to developing a zone refining process for plutonium metal.
Date: August 1, 1994
Creator: Blau, M. S.
System: The UNT Digital Library