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Beam Diagnosis and Lattice Modeling of the Fermilab Booster (open access)

Beam Diagnosis and Lattice Modeling of the Fermilab Booster

A realistic lattice model is a fundamental basis for the operation of a synchrotron. In this study various beam-based measurements, including orbit response matrix (ORM) and BPM turn-by-turn data are used to verify and calibrate the lattice model of the Fermilab Booster. In the ORM study, despite the strong correlation between the gradient parameters of adjacent magnets which prevents a full determination of the model parameters, an equivalent lattice model is obtained by imposing appropriate constraints. The fitted gradient errors of the focusing magnets are within the design tolerance and the results point to the orbit offsets in the sextupole field as the source of gradient errors. A new method, the independent component analysis (ICA) is introduced to analyze multiple BPM turn-by-turn data taken simultaneously around a synchrotron. This method makes use of the redundancy of the data and the time correlation of the source signals to isolate various components, such as betatron motion and synchrotron motion, from raw BPM data. By extracting clean coherent betatron motion from noisy data and separates out the betatron normal modes when there is linear coupling, the ICA method provides a convenient means to measure the beta functions and betatron phase advances. It also …
Date: September 1, 2005
Creator: Huang, Xiaobiao
System: The UNT Digital Library
Superresolution of buried objects in layered media by near-field electromagnetic imaging (open access)

Superresolution of buried objects in layered media by near-field electromagnetic imaging

None
Date: September 1, 2000
Creator: Lehman, S K
System: The UNT Digital Library
The Cryogenic Dark Matter Search (CDMS-II) Experiment: First Results from the Soudan Mine (open access)

The Cryogenic Dark Matter Search (CDMS-II) Experiment: First Results from the Soudan Mine

There is an abundance of evidence that the majority of the mass of the universe is in the form of non-baryonic non-luminous matter that was non-relativistic at the time when matter began to dominate the energy density. Weakly Interacting Massive Particles, or WIMPs, are attractive cold dark matter candidates because they would have a relic abundance today of {approx}0.1 which is consistent with precision cosmological measurements. WIMPs are also well motivated theoretically. Many minimal supersymmetric extensions of the Standard Model have WIMPs in the form of the lightest supersymmetric partner, typically taken to be the neutralino. The CDMS II experiment searches for WIMPs via their elastic scattering off of nuclei. The experiment uses Ge and Si ZIP detectors, operated at <50 mK, which simultaneously measure the ionization and athermal phonons produced by the scattering of an external particle. The dominant background for the experiment comes from electromagnetic interactions taking place very close to the detector surface. Analysis of the phonon signal from these interactions makes it possible to discriminate them from interactions caused by WIMPs. This thesis presents the details of an important aspect of the phonon pulse shape analysis known as the ''Lookup Table Correction''. The Lookup Table Correction …
Date: September 1, 2004
Creator: Chang, Clarence Leeder
System: The UNT Digital Library
A Search for Supersymmetric Higgs Bosons in the Di-tau Decay Mode in Proton - Anti-proton Collisions at 1.8 TeV (open access)

A Search for Supersymmetric Higgs Bosons in the Di-tau Decay Mode in Proton - Anti-proton Collisions at 1.8 TeV

A search for directly produced Supersymmetric Higgs Bosons has been performed in the di-tau decay channel in 86.3 {+-} 3.5 pb{sup -1} of data collected by CDF during Run1b at the Tevatron. They search for events where one tau decays to an electron and the other tau decays hadronically. They perform a counting experiment and set limits on the cross section for Higgs production in the high tan {beta} region of the m{sub A}-tan {beta} plane. For a benchmark parameter space point where m{sub A} = 100 and tan {beta} = 50, they set a 95% confidence level upper limit at 891 pb compared to the theoretically predicted cross section of 122 pb. For events where the tau candidates are not back-to-back, they utilize a di-tau mass reconstruction technique for the first time on hadron collider data. Limits based on a likelihood binned in di-tau mass from non-back-to-back events alone are weaker than the limits obtained from the counting experiment using the full di-tau sample.
Date: September 1, 2003
Creator: Connolly, Amy Lynn
System: The UNT Digital Library
Development of workflow planning software and a tracking study of the decay B+- --> J / Psi at the D0 Experiment (open access)

Development of workflow planning software and a tracking study of the decay B+- --> J / Psi at the D0 Experiment

A description of the development of the mc{_}runjob software package used to manage large scale computing tasks for the D0 Experiment at Fermilab is presented, along with a review of the Digital Front End Trigger electronics and the software used to control them. A tracking study is performed on detector data to determine that the D0 Experiment can detect charged B mesons, and that these results are in accordance with current results. B mesons are found by searching for the decay channel B{sup {+-}} {yields} J/{psi}K{sup {+-}}.
Date: September 1, 2003
Creator: Evans, David Edward
System: The UNT Digital Library
Kinetics of (beta)(right arrow)(delta) Solid-Solid Phase Transition of HMX (open access)

Kinetics of (beta)(right arrow)(delta) Solid-Solid Phase Transition of HMX

In order to calculate the kinetic parameters from DSC data, we have used the generally accepted methods of Bershtein [13]. We have calculated the rate constants for 4 temperatures and the activation energy based on the shift in the transition temperature, {beta} {yields} {delta} for HMX. The values of E{sub a} from this work is 402 kJ/mol compared to previous results by Brill [9] of 204 kJ/mol. Brill and associates measured the phase transition of HMX using FTIR, sodium chloride plates and silicon oil. Given the differences in technique between FTIR and DSC the results found in this work are reasonable. In this investigation a large sample set (16) proved to be statistically valid for the determinations of k. Linear regressions were performed, observed and good fits were obtained, for each temperature. The enthalpy determination of {Delta}H{sub o}, for the {beta} {yields} {delta} phase transition was reproducible with in 3 parts in 100 over the range of this experiment. Thus, the data derived from this experiment k, E{sub a}, and {Delta}H{sub o} are valid parameters for the solid-solid phase transition. Obtaining pure {beta} phase HMX was very important for this investigation. Related to the phase change is the particle size …
Date: September 1, 2000
Creator: Weese, R K
System: The UNT Digital Library
Carbon doping of III-V compound semiconductors (open access)

Carbon doping of III-V compound semiconductors

Focus of the study is C acceptor doping of GaAs, since C diffusion coefficient is at least one order of magnitude lower than that of other common p-type dopants in GaAs. C ion implantation results in a concentration of free holes in the valence band < 10% of that of the implanted C atoms for doses > 10{sup 14}/cm{sup 2}. Rutherford backscattering, electrical measurements, Raman spectroscopy, and Fourier transform infrared spectroscopy were amonth the techniques used. Ga co-implantation increased the C activation in two steps: first, the additional radiation damage creates vacant As sites that the implanted C can occupy, and second, it maintains the stoichiometry of the implanted layer, reducing the number of compensating native defects. In InP, the behavior of C was different from that in GaAs. C acts as n-type dopant in the In site; however, its incorporation by implantation was difficult to control; experiments using P co-implants were inconsistent. The lattice position of inactive C in GaAs in implanted and epitaxial layers is discussed; evidence for formation of C precipitates in GaAs and InP was found. Correlation of the results with literature on C doping in III-V semiconductors led to a phenomenological description of C in …
Date: September 1, 1994
Creator: Moll, A. J.
System: The UNT Digital Library
Laser trapping of {sup 21}Na atoms (open access)

Laser trapping of {sup 21}Na atoms

This thesis describes an experiment in which about four thousand radioactive {sup 21}Na (t{sub l/2} = 22 sec) atoms were trapped in a magneto-optical trap with laser beams. Trapped {sup 21}Na atoms can be used as a beta source in a precision measurement of the beta-asymmetry parameter of the decay of {sup 21}Na {yields} {sup 21}Ne + {Beta}{sup +} + v{sub e}, which is a promising way to search for an anomalous right-handed current coupling in charged weak interactions. Although the number o trapped atoms that we have achieved is still about two orders of magnitude lower than what is needed to conduct a measurement of the beta-asymmetry parameter at 1% of precision level, the result of this experiment proved the feasibility of trapping short-lived radioactive atoms. In this experiment, {sup 21}Na atoms were produced by bombarding {sup 24}Mg with protons of 25 MeV at the 88 in. Cyclotron of Lawrence Berkeley Laboratory. A few recently developed techniques of laser manipulation of neutral atoms were applied in this experiment. The {sup 21}Na atoms emerging from a heated oven were first transversely cooled. As a result, the on-axis atomic beam intensity was increased by a factor of 16. The atoms in …
Date: September 1, 1994
Creator: Lu, Zheng-Tian
System: The UNT Digital Library
The Mirrortron experiment: A proof of principle test for a method of generating high transient potentials (open access)

The Mirrortron experiment: A proof of principle test for a method of generating high transient potentials

The Mirrortron is a concept in which heavy ions are accelerated by a large local transient space potential that is produced in a hot electron plasma. The purpose of this experiment is to begin a proof of principle experiment to investigate the feasibility of producing this space potential and its associated electric field. If a large magnetic field is suddenly generated in a hot electron plasma with a loss-cone distribution, then potentials on the order of the electron temperature are expected. This potential lasts a few tens of nanoseconds. The investigation begins with a theoretical analysis of this phenomenon giving the space potential as a function of the applied magnetic field. The theory is further extended to cases of relativistic electron distributions. This is then followed by design work on a mirror confinement system for hot electrons. In this experiment a 50--100 keV electron temperature plasma is created with electron cyclotron resonance heating using two frequencies of relatively low microwave power. The microwaves are coupled to resonant frequencies of the vacuum chamber. The volume averaged plasma density is measured to be in the 10{sup 9} cm{sup {minus}3} range. A strap coil and a flat Blumlein transmission line pulse generator were …
Date: September 1, 1993
Creator: Douglass, S. R.
System: The UNT Digital Library
Application of an Electrochemical Quartz Crystal Microbalance to the study of electrocatalytic films (open access)

Application of an Electrochemical Quartz Crystal Microbalance to the study of electrocatalytic films

The EQCM was used to study the deposition and composition of electrodeposited pure PbO{sub 2} and Bi-doped PbO{sub 2} active toward anodic oxygen-transfer reactions. Within the doped films, Bi is incorporated as Bi{sup +5} in the form of BiO{sub 2}A, where A is ClO{sub 4}{sup {minus}} or NO{sub 3}{sup {minus}}. For deposition of these 2 materials, changes in hydration between the Au oxide and the depositing film resulted in higher mass-to-charge ratios. XRD and XPS were used to study the films; the rutile structure of PbO{sub 2} is retained even with the Bi doping. The EQCM was also used to study the formation and dissolution of Au oxide and preoxide structures formed on the Au substrate electrodes in acidic media. The preoxide structures were AuOH and increased the surface mass. For the formation of stable Au films on quartz wafers, Ti interlayers between Au and quartz was found to be very effective.
Date: September 1, 1993
Creator: Gordon, J. S., Jr.
System: The UNT Digital Library
The synthesis and structural characterization of novel transition metal fluorides (open access)

The synthesis and structural characterization of novel transition metal fluorides

High purity KMF{sub 6} and K{sub 2}MF{sub 6} salts (M = Mo,Re, Ru, Os, Ir, Pt) are obtained from reduction hexafluorides. A rhombohedral unit cell is observed for KReF{sub 6}. Fluoride ion capture by Lewis acids from the hexafluorometallate (IV) salts affords high purity tetrafluorides for M = Mo, Re, Ru, Os, and Pd. The structure of RuF{sub 4} is determined from X-ray synchrotron and neutron powder data. Unit cells based on theorthorhombic PdF{sub 4} type cell are derived from X-ray powder data for ReF{sub 4} and OsF{sub 4}. Fluoride ion capture from KAgF{sub 4} provides the thermally unstable trifluoride as a bright, red, diamagnetic solid. The structure solution of AgF{sub 3} and redetermination of the AuF{sub 3} structure from X-ray synchrotron and neutron powder data demonstrate that the two are isostnictural. Thermal decomposition product of AgF{sub 3} is the mixed valence compound Ag{sup II}Ag{sub 2}{sup III}F{sub 8}. Several new salts containing the (Ag - F){sub n}{sup n+} chain cation are prepared. The first linear (Ag - F){sub n}{sup n+} chain is observed in AgF{sup +}BF{sub 4 {sup {minus}}} which crystallizes in a tetragonal unit. AgFAuF{sub 4} has a triclinic unit cell and is isostructural with CuFAuF{sub 4}. AgFAuF{sub 6} …
Date: September 1, 1992
Creator: Casteel, W. J. Jr.
System: The UNT Digital Library
CCM Continuity Constraint Method: A finite-element computational fluid dynamics algorithm for incompressible Navier-Stokes fluid flows (open access)

CCM Continuity Constraint Method: A finite-element computational fluid dynamics algorithm for incompressible Navier-Stokes fluid flows

As the field of computational fluid dynamics (CFD) continues to mature, algorithms are required to exploit the most recent advances in approximation theory, numerical mathematics, computing architectures, and hardware. Meeting this requirement is particularly challenging in incompressible fluid mechanics, where primitive-variable CFD formulations that are robust, while also accurate and efficient in three dimensions, remain an elusive goal. This dissertation asserts that one key to accomplishing this goal is recognition of the dual role assumed by the pressure, i.e., a mechanism for instantaneously enforcing conservation of mass and a force in the mechanical balance law for conservation of momentum. Proving this assertion has motivated the development of a new, primitive-variable, incompressible, CFD algorithm called the Continuity Constraint Method (CCM). The theoretical basis for the CCM consists of a finite-element spatial semi-discretization of a Galerkin weak statement, equal-order interpolation for all state-variables, a 0-implicit time-integration scheme, and a quasi-Newton iterative procedure extended by a Taylor Weak Statement (TWS) formulation for dispersion error control. Original contributions to algorithmic theory include: (a) formulation of the unsteady evolution of the divergence error, (b) investigation of the role of non-smoothness in the discretized continuity-constraint function, (c) development of a uniformly H{sup 1} Galerkin weak statement …
Date: September 1, 1993
Creator: Williams, P. T.
System: The UNT Digital Library
Quantitative evaluation of material composition of composites using x-ray energy-dispersive NDE technique (open access)

Quantitative evaluation of material composition of composites using x-ray energy-dispersive NDE technique

This technique worked well for determining the thickness and densities for composite components having the higher linear attenuation coefficient; it accurately determined thickness of epoxy-resin and Al metal, and the denisty of bone, to {le} 4% in the graphite-epoxy, bone-plexiglas, and Al-Al corrosion composites. Accuracy is dictated by the magnitude and uncertainty of the linear attenuation coefficient. Use of Ge detector and multichannel analyzer are limited by inspection time (1 day for point measurement) and access limitation. Immediate development of a rapid in-service inspection tool is limited by the amplifier and MCA systems. The MCA should be replaced with a single-channel analyzer, and an electronic device should be built for monitoring the incoming signal for Pile-Up-Rejection.
Date: September 1, 1993
Creator: Ting, J.
System: The UNT Digital Library
The incongruent melting and melt textured solidification process of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (open access)

The incongruent melting and melt textured solidification process of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}

The melting and solidification was studied using in-situ high temperature XRD from melting point to 900{degree}C in 0.2, 0.1, 0.02 atm O{sub 2} and pure N{sub 2}. The incongruent melting point of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} was lowered by decreasing the partial O{sub 2} pressure from 870C (in .2 atm O{sub 2}) to 830C (in pure N{sub 2} atmosphere). As temperature was increased the incongruent melting of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} followed a phase sequence in which (Ca, Sr)CuO{sub 2} {r_arrow} (Ca, Sr)CuO{sub 2} {r_arrow} (Ca,Sr)O occur in presence of Bi-rich liquid. At 900C, the only crystalline phase present in the melt was (Ca,Sr)O. This phase sequence remained the same for all four different partial O{sub 2} pressures. During the solidification of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, from 10C below the melting point to 760C, the major phases that form depend on the partial O{sub 2} pressure. As partial O{sub 2} pressures was lowered from 0.2 to 0 atm, the major second phase formation out of the melt follows the sequence of (Ca, Sr)CuO{sub 2} {r_arrow} (Ca, Sr)CuO{sub 2} {r_arrow} (Ca,Sr)O respectively. At 0.1 Atm partial O{sub 2} pressure and below, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} solidified out …
Date: September 1, 1993
Creator: Polonka, J.
System: The UNT Digital Library
Reduction of plyatomic ion interferences in indictively coupled plasma mass spectrometry with cryogenic desolvation (open access)

Reduction of plyatomic ion interferences in indictively coupled plasma mass spectrometry with cryogenic desolvation

A desolvation scheme for introducing aqueous and organic samples into an argon inductively coupled plasma is described; the aerosol generated by nebulizer is heated (+140 C) and cooled ({minus}80 C) repeatedly, and the dried aerosol is then injected into the mass spectrometer. Polyatomic ions are greatly suppressed. This scheme was validated with analysis of seawater and urine reference samples. Finally, the removal of organic solvents by cryogenic desolvation was studied.
Date: September 1, 1993
Creator: Alves, L. C.
System: The UNT Digital Library
Thermally-generated reactive intermediates: Trapping of the parent ferrocene-based o-quinodimethane and reactions of diradicals generated by hydrogen-atom transfers (open access)

Thermally-generated reactive intermediates: Trapping of the parent ferrocene-based o-quinodimethane and reactions of diradicals generated by hydrogen-atom transfers

Ferrocenocyclobutene is prepared by flash vacuum pyrolysis (FVP) of the N-amino-2-phenylaziridine hydrazone of 2-methylferrocenealdehyde. In the second section of this dissertation, a series of hydrocarbon rearrangements were observed. FVP of o-allyltoluene at 0.1 Torr (700--900 C) gives 2-methylindan and indene, accompanied by o-propenyltoluene. FVP of 2-methyl-2`-vinylbiphenyl gives 9-methyl-9,10-dihydrophenanthrene, which fits the proposed mechanism. However, FVP of 2-(o-methylbenzyl)styrene gives mainly anthracene and 1-methylanthracene. This cyclization reaction was also successful with o-allylphenol and o-(2-methylallyl)phenol.
Date: September 1, 1993
Creator: Ferguson, J. M.
System: The UNT Digital Library
Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors (open access)

Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors

The motivation of this work is to develop high reflectance normal-incidence multilayer mirrors in the 8-12 nm wavelength region for applications in astronomy and extreme ultraviolet lithography. To achieve this goal, Mo/Sr and Mo/Y multilayers were studied. These multilayers were deposited with a UHV magnetron sputtering system and their reflectances were measured with synchrotron radiation. High normal-incidence reflectances of 23% at 8.8 nm, 40.8% at 9.4 nm, and 48.3% at 10.5 nm were achieved. However, the reflectance of Mo/Sr multilayers decreased rapidly after exposure to air. Attempts to use thin layers of carbon to passivate the surface of Mo/Sr multilayers were unsuccessful. Experimental results on the refractive index {tilde n} = 1-{delta} + i{beta} of yttrium and molybdenum in the 50-1300 eV energy region are reported in this work. This is the first time ever that values on the refractive index of yttrium are measured in this energy range. The absorption part {beta} was determined through transmittance measurements. The dispersive part {delta} was calculated by means of the Kramers-Kronig formalism. The newly determined values of the refractive index of molybdenum are in excellent agreement with the published data. Those of yttrium are more accurate and contain fine structures around the …
Date: September 1, 2002
Creator: Kjornrattanawanich, B
System: The UNT Digital Library
Climb of Dislocations in Magnesium Oxide Single Crystals (open access)

Climb of Dislocations in Magnesium Oxide Single Crystals

The wave like pattern, observed in dislocation dipoles of uniform spacing during annealing, which starts from the ends of the dipole and gets damped toward the centre, has been attributed to controlled vacancy migration. A theory has been set-up to give activation energy for the process, 60,700 + 2,000 cal/mole. This value has been compared with an independent study of pipe diffusion, in which a prismatic loop inside the foil is connect to both surfaces of the foil by screw dislocation.
Date: September 1, 1970
Creator: Narayan, Jagdish
System: The UNT Digital Library
Chaos and simple determinism in reversed field pinch plasmas: Nonlinear analysis of numerical simulation and experimental data (open access)

Chaos and simple determinism in reversed field pinch plasmas: Nonlinear analysis of numerical simulation and experimental data

In this dissertation the possibility that chaos and simple determinism are governing the dynamics of reversed field pinch (RFP) plasmas is investigated. To properly assess this possibility, data from both numerical simulations and experiment are analyzed. A large repertoire of nonlinear analysis techniques is used to identify low dimensional chaos in the data. These tools include phase portraits and Poincare sections, correlation dimension, the spectrum of Lyapunov exponents and short term predictability. In addition, nonlinear noise reduction techniques are applied to the experimental data in an attempt to extract any underlying deterministic dynamics. Two model systems are used to simulate the plasma dynamics. These are the DEBS code, which models global RFP dynamics, and the dissipative trapped electron mode (DTEM) model, which models drift wave turbulence. Data from both simulations show strong indications of low dimensional chaos and simple determinism. Experimental date were obtained from the Madison Symmetric Torus RFP and consist of a wide array of both global and local diagnostic signals. None of the signals shows any indication of low dimensional chaos or low simple determinism. Moreover, most of the analysis tools indicate the experimental system is very high dimensional with properties similar to noise. Nonlinear noise reduction …
Date: September 1, 1993
Creator: Watts, C. A.
System: The UNT Digital Library
Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements (open access)

Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with {sup 241}Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He{sup +} or 10-MeV Si{sup 3+}. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair ({epsilon}{sub di}) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.
Date: September 1, 1993
Creator: Han, S. S.
System: The UNT Digital Library
Localization from near-source quasi-static electromagnetic fields (open access)

Localization from near-source quasi-static electromagnetic fields

A wide range of research has been published on the problem of estimating the parameters of electromagnetic and acoustical sources from measurements of signals measured at an array of sensors. In the quasi-static electromagnetic cases examined here, the signal variation from a point source is relatively slow with respect to the signal propagation and the spacing of the array of sensors. As such, the location of the point sources can only be determined from the spatial diversity of the received signal across the array. The inverse source localization problem is complicated by unknown model order and strong local minima. The nonlinear optimization problem is posed for solving for the parameters of the quasi-static source model. The transient nature of the sources can be exploited to allow subspace approaches to separate out the signal portion of the spatial correlation matrix. Decomposition techniques are examined for improved processing, and an adaptation of MUtiple SIgnal Characterization (MUSIC) is presented for solving the source localization problem. Recent results on calculating the Cramer-Rao error lower bounds are extended to the multidimensional problem here. This thesis focuses on the problem of source localization in magnetoencephalography (MEG), with a secondary application to thunderstorm source localization. Comparisons are …
Date: September 1, 1993
Creator: Mosher, J. C.
System: The UNT Digital Library
Study of the effect of humidity, particle hygroscopicity and size on the mass loading capacity of HEPA filters (open access)

Study of the effect of humidity, particle hygroscopicity and size on the mass loading capacity of HEPA filters

The effect of humidity, particle hygroscopicity and size on the mass loading capacity of glass fiber HEPA filters has been studied. At humidifies above the deliquescent point, the pressure drop across the HEPA filter increased non-linearly with the areal loading density (mass collected/filtration area) of NaCl aerosol, thus significantly reducing the mass loading capacity of the filter compared to dry hygroscopic or non-hygroscopic particle mass loadings. The specific cake resistance, K{sub 2}, has been computed for different test conditions and used as a measure of the mass loading capacity. K. was found to decrease with increasing humidity for the non-hygroscopic aluminum oxide particles and the hygroscopic NaCl particles (at humidities below the deliquescent point). It is postulated that an increase in humidity leads to the formation of a more open particulate cake which lowers the pressure drop for a given mass loading. A formula for predicting K{sub 2} for lognormally distributed aerosols (parameters obtained from impactor data) is derived. The resistance factor, R, calculated using this formula was compared to the theoretical R calculated using the Rudnick-Happel expression. For the non-hygroscopic aluminum oxide the agreement was good but for the hygroscopic sodium chloride, due to large variation in the cake …
Date: September 1, 1992
Creator: Gupta, A.
System: The UNT Digital Library
Design and construction of a imaging instrument for studying ion emission from pure ion emitters (open access)

Design and construction of a imaging instrument for studying ion emission from pure ion emitters

The development of new ion sources is important in the area of surface analysis to make it easier to perform more sensitive and accurate analyses. In surface analysis a primary ion beam composed of a single species can help when predicting and interpreting the results. Therefore, much interest and effort has been focused on producing pure ion emitters. An instrument has been designed and constructed to view the current densities of the ions being emitted from pure ion emitters. The instrument electrostatically accelerates and focuses the ion beam onto a microchannel plate detector equipped with a phosphor screen for viewing the images. These images are used to identify areas of enhanced ion emission. Once these areas are identified, the investigator can use other instruments to analyze them, and hopefully develop a better understanding of the chemistry and physics involved in the ion emission process. A computer based control system has been integrated into the system to simplify the operation of the instrument and provide safety features to protect the hardware from damage. A closed-circuit video camera system is used to allow the images to be remotely viewed during imaging procedures. Experiments show that the instrument has a lower detection limit …
Date: September 1, 1993
Creator: Olson, J. E.
System: The UNT Digital Library
On the hypothesis that quantum mechanism manifests classical mechanics: Numerical approach to the correspondence in search of quantum chaos (open access)

On the hypothesis that quantum mechanism manifests classical mechanics: Numerical approach to the correspondence in search of quantum chaos

Quantum manifestation of classical chaos has been one of the extensively studied subjects for more than a decade. Yet clear understanding of its nature still remains to be an open question partly due to the lack of a canonical definition of quantum chaos. The classical definition seems to be unsuitable in quantum mechanics partly because of the Heisenberg quantum uncertainty. In this regard, quantum chaos is somewhat misleading and needs to be clarified at the very fundamental level of physics. Since it is well known that quantum mechanics is more fundamental than classical mechanics, the quantum description of classically chaotic nature should be attainable in the limit of large quantum numbers. The focus of my research, therefore, lies on the correspondence principle for classically chaotic systems. The chaotic damped driven pendulum is mainly studied numerically using the split operator method that solves the time-dependent Schroedinger equation. For classically dissipative chaotic systems in which (multi)fractal strange attractors often emerge, several quantum dissipative mechanisms are also considered. For instance, Hoover`s and Kubo-Fox-Keizer`s approaches are studied with some computational analyses. But the notion of complex energy with non-Hermiticity is extensively applied. Moreover, the Wigner and Husimi distribution functions are examined with an equivalent …
Date: September 1, 1993
Creator: Lee, Sang-Bong
System: The UNT Digital Library