Microbial production of natural gas in subsurface organic-rich reservoirs (e.g. coal, shale, oil) can be enhanced by the introduction of limiting nutrients to stimulate microbial communities to generate “new” methane resources on human timescales. The few successful field experiments of Microbial Enhancement of Coalbed Methane (MECoM) relied on relatively qualitative approaches for estimating the amount of “new” methane produced during the stimulation process (i.e. extrapolation of pre-stimulation gas production curves). We have tested deuterated water as a tracer, initially in the laboratory, to more directly quantify the amount of “new” methane generated and the effectiveness of MECoM stimulation approaches. Microorganisms, formation water, and coal obtained during a previous drilling project in the Powder River Basin, Birney, Montana were used to set up a series of benchtop stimulation experiments where we added incremental amounts of deuterated water to triplicate sets of stimulated microbes (methanogens). We hypothesized that as MECoM progresses, methanogens will incorporate the heavy water into new methane produced, as methanogens naturally uptake hydrogen during methanogenesis. The amount of hydrogen incorporated into methane from water is dependent on the methanogenic pathway (hydrogenotropic vs acetoclastic/methylotrophic). During the experiments, we saw a shift in the methanogenic pathway towards acetoclastic methanogenesis, which was indicated by a consistent shift in the enrichment of deuterium in the methane produced, methanogenic community, and a large kinetic fractionation. The enrichment of the methane as compared to the deuterium content of the water the microbes used followed a narrowly confined, predictable range of values. This predictable enrichment of the methane allows us to propose a quantification scheme for the amount of methane produced in larger field scale stimulations, as we can compare the change in the overall deuterium content of the in-situ methane with the known value before the stimulation. The success of our proof-of-concept laboratory experiments suggests that deuterium may be used as a tracer of “new” natural gas resources in field- to commercial-scale MECoM projects. In addition, additions of deuterated water may also be useful as a tracer in bioremediation projects where large background pools of contaminants or degradation products hamper traditional quantification techniques, microbial enhanced oil recovery, or other subsurface carbon cycling pathways.

This thesis describes measurements of the pion induced pion production reaction π⁺d → π⁺π⁻p p performed with a 280 MeV incident π⁺ beam at TRIUMF. The data are compared with an improved version of the Oset and Vicente-Vacas theoretical model [12]. The goal of the experiment and of the analysis was to provide a larger body of data for the free reaction and to test the validity of theoretical models. In the process, the ability to determine the values of the coupling constants C, f∆ , gN*∆π within such a model framework would be explored. The knowledge of the precise value of these coupling constants would constrain N* decay branching ratios and other pion induced reaction mechanisms like Double Charge Exchange. A previous experiment [23] had indicated that the pion induced pion production on deuterium is essentially a quasifree process with the reaction occurring on the neutron leaving the proton merely a spectator. The main difference with respect to the free reaction is the effect of Fermi motion of the neutron. Although we were interested in studying the free reaction (π⁻p → π⁺π⁻n), we chose a deuterium target so that the experiment could be run with a π⁺beam, since the π⁻ beam flux is about 6 times lower than the flux of the positive pion beam at 280 MeV, the energy at which our experiment was performed. Such a flux would have required a much longer running time for the experiment in order to achieve the same statistical accuracy. The quasifree nature of the process was also confirmed in our experiment. This experiment involved a coincidence measurement of the quasifree process and as such provided four-fold differential cross section spectra of the reaction thus allowing for a microscopic comparison between data and theoretical models. In the theoretical description we incorporated additional amplitudes for the N* → N(ππ)p-wave diagrams required to describe the reaction cross section at Tπ = 280 MeV. We also added the Fermi motion of the nucleon to the model to account for the deuterium environment. The 'free' parameters of the model are the largely unknown coupling constants listed above. We fixed C to be -2.08 by requiring the energy dependence of the model to be that of the measurement of [22] and compared the energy and angular distributions of the model to our data for several values of the f∆ and gN*∆π coupling constants ranging between 0 and 2 (where the units are 4/5 fNNπ) and between 1.08 and 1.53 respectively. We found reasonable sensitivity of the model to the f∆ variation, but only limited sensitivity to the value of the gN*∆π coupling constant. Overall we achieved a very good agreement between data and the theoretical predictions for f∆ values smaller than 0.5 and gN*∆π values closer to its lower limit. Improved statistical accuracy of the data would however be needed to better constrain the values of the coupling constants. On the basis of our results we feel that this model is a useful tool for planning future experiments and that a more extensive (π, 2π) experimental program, where differential cross sections are measured for differing isospin channels, would provide a further, more stringent test on the model allowing for a more precise determination of the coupling constants. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Mono-energetic neutrons have been produced with the low-voltage Cockroft-Walton accelerator at North Texas State College using two different reactions. It is the purpose of this paper to report the angular distribution and total flux of the neutrons obtained from the T(D,n) reaction.

Includes bibliographical references. / The origin of the experimentally observed density dependence of the effective muon alpha sticking fraction will in muon catalyzed deuterium- tritium fusion has been comprehensively reanalyzed with the particular emphasis put on the density dependence of the stopping power in dense hydrogen. The main technical details and improvements in this work are: The (aμ)+ 2s and 2p states are treated independently and are assigned individual reaction rates. The essential muonic excitation rates have been recalculated taking into account finite nuclear mass effects. The stopping power for a charged projectile in liquid heavy hydrogen is modified to account for dynamic screening effects and a density dependent effective ionization potential. It is shown that the medium dependent stopping power for the (aμ)+ ion is the crucial entity controlling the density dependance of the effective sticking fraction. It is also pointed out that the muonic helium Ka X-ray yield and the sticking fraction at high density can not be simultaneously brought into agreement with the experimental results without invoking novel mechanisms suppressing Stark mixing in the (Heμ) L-shell.

Includes bibliographical references. / A Monte Carlo code MUGLU has been, written for the simulation of experiments to measure alpha-muon sticking in muon catalysed deuterium-tritium fusion. The experiments simulated are those which measure the ratio of αμ to α from fusion in a low density gas target by detecting collinear alpha-neutron coincidences and relying on the differing stopping powers of the α and αμ ions. The Monte Carlo simulations provide estimates of geometrical and detection efficiency factors required for the calculation of the sticking coefficient from the experimental measurements. Simulations have been made of alternative experimental geometries in order to investigate the α-neutron coincidence signature and other characteristics of existing and proposed systems. The characteristics of a neutron detector used in, one of the current sticking experiments (Rutherford Appleton Laboratory) have been studied experimentally, as well as simulated, using the T(d,n)α reaction to emulate the fusion source. The results obtained show that the dependence of the neutron detection efficiency on the position and angle of neutron incidence on the detector is significant and should be taken into account when determining sticking coefficients from alpha-neutron coincidence measurements.

The purpose of this investigation was to determine the deuterium oxide content of various samples of water by a precise and sensitive method based upon the compressibility of water. These samples were gathered from as many different locations as were deemed necessary.

<p> The regioselectivities of bromination and deuterium exchange of 2-butanone are shown to be the same, under identical conditions. This work firmly establishes that enolization is the rate-determining step for the former reaction, contrary to some recent reports in the literature.</p> <p> The steric effects and activation parameters in the bimolecular nucleophilic displacement reactions of a series of α-haloketones and alkyl halides are shown to be inconsistent with either a bridging or conjugation mechanism for the observed rate enhancements of haloketone over alkyl halide.</p> <p> The stereoelectronic requirements of this mechanism are tested in a system where the stereochemistry is known (cis- and trans-chlorocyclohexanones). The activation parameters suggest that only in the case where the geometry is correct for maximum conjugation (trans-chlorocyclohexanone) is there an appreciable difference in mechanism (stereoelectronically) from displacement at ordinary saturated carbon.</p> / Thesis / Doctor of Philosophy (PhD)

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