Pulsed neutron capture (PNC) logs are commonly used for formation evaluation behind casing and to assess time-lapse variations of hydrocarbon pore volume. Because conventional interpretation methods for sigma logs assume homogeneous formations, errors may arise, especially in thinly-bedded formations, when appraising petrophysical properties of hydrocarbon-bearing beds. There exist no quantitative interpretation methods to account for shoulder-bed effects on sigma logs acquired in sand-shale laminated reservoirs. Because of diffusion effects between dissimilar beds, sigma logs acquired in such formations do not obey mixing laws between the sigma responses of pure-sand and pure-shale end members of the sedimentary sequence. We introduce a new numerical method to simulate rapidly and accurately PNC logs. The method makes use of late-time, thermal-neutron flux sensitivity functions (FSFs) to describe the contribution of multi-layer formations toward the measured capture cross section. It includes a correction procedure based on 1D neutron diffusion theory that adapts the transport-equation-derived, base-case FSF of a homogeneous formation to simulate the response of vertically heterogeneous formations. Benchmarking exercises indicate that our simulation method yields average differences smaller than 2 c.u. within seconds of CPU time with respect to PNC logs simulated with rigorous Monte Carlo methods for a wide range of geometrical, petrophysical, and fluid properties. We develop an inversion method to reduce shoulder-bed effects on pulsed neutron capture (PNC) logs in the estimation of layer-by-layer capture cross sections, Σ. The method is based on the previously developed rapid approximation of PNC logs. Tests performed on synthetic examples that include a variety of lithology, saturating-fluid, and bed-thickness configurations confirm the efficiency, reliability, and stability of the inversion procedure. Inversion consistently improves the vertical resolution and Σ definition of PNC logs across beds thinner than 45 cm. Our fast, iterative algorithm inverts sigma logs in seconds of CPU time, and is therefore suitable for joint petrophysical interpretation with other open- and cased-hole logs. / text

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High energy particle irradiation inevitably generates defects in solids in the form of collision cascades. The ballistic formation and thermalization of cascades occur rapidly and are believed to be reasonably well understood. However, knowledge of the evolution of defects after damage cascade thermalization, referred to as dynamic annealing, is quite limited. Unraveling the mechanisms associated with dynamic annealing is crucial since such processes play an important role in the formation of stable post-irradiation disorder in ion-beam-processed semiconductors and determines the “radiation tolerance” of many nuclear materials. The purpose of this dissertation is to further our understanding of the processes involved in dynamic annealing. In order to achieve this, two main tasks are undertaken. First, the effects of dynamic annealing are investigated in ZnO, a technologically relevant material that exhibits very high dynamic defect annealing at room temperature. Such high dynamic annealing leads to unusual defect accumulation in heavy ion bombarded ZnO. Through this work, the puzzling features that were observed more than a decade ago in ion-channeling spectra have finally been explained. We show that the presence of a polar surface substantially alters damage accumulation. Non-polar surface terminations of ZnO are shown to exhibit enhanced dynamic annealing compared to polar surface terminated ZnO. Additionally, we demonstrate one method to reduce radiation damage in polar surface terminated ZnO by means of a surface modification. These results advance our efforts in the long-sought-after goal of understanding complex radiation damage processes in ceramics. Second, a pulsed-ion-beam method is developed and demonstrated in the case of Si as a prototypical non-metallic target. Such a method is shown to be a novel experimental technique for direct extraction of dynamic annealing parameters. The relaxation times and effective diffusion lengths of mobile defects during the dynamic annealing process play a vital role in damage accumulation. We demonstrate that these parameters dominate the formation of stable post-irradiation disorder. In Si, a defect lifetime of ∼ 6 ms and a characteristic defect diffusion length of ∼ 30 nm are measured. These results should nucleate future pulsed-beam studies of dynamic defect interaction processes in technologically relevant materials. In particular, understanding length- and time-scales of defect interactions are essential for extending laboratory findings to nuclear material lifetimes and to the time-scales of geological storage of nuclear waste.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Some pages left blank intentionally. Includes bibliographical references (leaves 125-130). Also available on the World Wide Web.

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 52-53).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: PPT; pulsed plasma thruster; Langmuir probe; plasma diagnostics; electric propulsion; electron temperature; electron density. Includes bibliographical references (p. 97-102).

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 5, 2009). Thesis advisor: Dr. Scott Kovaleski. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Nov. 20, 2008). PDF text: xvii, 187 p. : ill. (some col.) ; 11 Mb. UMI publication number: AAT 3311304. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph.D.)--University of California, Berkeley, 1960. / "Physics & Mathematics, UC-34" -t.p. "TID-4500 (15th Ed.)" -t.p. Includes bibliographical references.