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Samples of pure nickel have been implanted with 500keV helium ions, at a dose of 10[17]ions/cm[2], followed by annealing in vacuo at 750°C (≈0.6T[m]) for various time periods to allow bubble nucleation and growth to occur. A transverse sectioning technique has been developed to allow TEM studies of the complete depth distribution of cavities, hence allowing the mechanisms for bubble growth at 750°C in nickel to be identified. It was found that after 2 hours annealing, a fine layer of cavities developed, corresponding well with the gas deposition profile calculated using the E-DEP-1 code. Subsequent annealing resulted in cavity growth on the periphery of the layer by vacancy collection, the principal vacancy sources being the irradiated surface and grain boundaries in the bulk of the material. Cavity growth in the peak implanted region was found to be suppressed due to the lack of vacancies and with bubble migration being hindered as a result of high bubble pressures, hence migration and coalescence did not occur until cavities approached their equilibrium pressure. The same bubble growth mechanisms were found to prevail after implantation of 5x10[16]ions/cm[2] and also after 250keV He implantation. The growth of helium bubbles has been compared to neon bubbles after implantation with 500keV Ne ions at two doses: 7.8x10[16]ions/cm[2] to obtain the same peak gas concentration and 2.9x10[15]ions/cm[2] to achieve the same peak displacement damage, followed by annealing. The cavity density was found to be established by the gas concentration, the displacement damage apparently having little or no effect, even after an approximately 27-fold increase. The growth mechanisms observed after Ne implantation appeared to be the same as those for He, although the bubbles after low dose Ne implantation achieved equilibrium conditions more rapidly, due to the lack of implanted gas. He and Ne have been compared after high energy implantation at 500°C, in the Variable Energy Cyclotron at Harwell to a peak gas concentration of 250ppm. For 4MeV He, an inhomogeneous cavity distribution was observed, compared to a relatively uniform cavity layer after 17MeV Ne implantation. However, the observed cavity sizes and number densities were found to be similar. Finally, nickel has been irradiated at 500°C with a mixed beam of 51MeVNi[6+]/17MeVNe[2+] ions, to 250ppm Ne together with 30dpa displacement damage, and compared to an irradiation with 51MeVNi[6+] ions without inert gas, as well as with 17MeVNe[2+] ions. The void number density profile resulting from the single heavy ion irradiation was similar to the computed damage profile, although the peak was ≈10% deeper than that predicted. A depression in the swelling profile was observed in this peak region resulting from a reduction in cavity size, a bimodal distribution being observed. The effect of simultaneous gas deposition was to increase the cavity nucleation and reduce cavity size. This phenomenon was found to be dominant in the region corresponding to the implanted gas layer, however the gas appeared to influence cavities produced at greater depths, with an overall reduction in swelling.

Thesis (Ph. D.)--University of California, San Diego, 1999. / Vita. Includes bibliographical references (leaves 275-287).

An examination of the role of experiment in the cold fusion controversy is offered. It is argued that experimental results served as rhetorical tools in the service of actors in the controversy. Discourse analysis informed by actor network theory is employed to analyze the verbal and textual discourse of scientists involved in the construction of experimentally-based scientific knowledge. The practices actors employed to structure their discourse for rhetorical effectiveness are investigated. I conclude that if experiments are to retain their traditional role as arbiters of knowledge claims, the unit of analysis pertaining to "experiment" must be broadened to include not only experimental practices within the laboratory, but also the multitude of practices scientists perform outside the laboratory walls in order to increase the likelihood that their knowledge claims will be adopted by their disciplinary matrix. / Master of Science

<p>High power fusion plasmas produced in the world’s largest facility for magnetic confinement experiments (JET), have been studied using the neutron emission measured with the magnetic proton recoil (MPR) spectrometer. The MPR has been used to observe plasmas since 1996 including those of deuterium-tritium leading to several fusion records and corresponding observational achievements of neutron emission spectroscopy. Noteworthy are novel studies of the complex states of fuel ions arising through plasma heating by neutral beam (NB) injection and radio frequency (RF) power.</p><p>This thesis concerns the analysis of MPR data on the neutron emission from NB heated discharges alone and in combination with RF. A main objective of these studies has been the effect of supra-thermal fuel ion reactions on the fusion power as compared to the basic thermal component. The analysis was based on dedicated models to describe the velocity distributions of the ion population under the influence of the NB and RF heating in a parametric form allowing trial neutron spectra to be calculated and fitted to the data to select the kinetic state of the fuel ions that best described the MPR observations.</p><p>Spectral signatures of different underlying plasma states and phenomena were identified and results from up to five different ion reaction contributions to the fusion power were demonstrated besides the global plasma features of toroidal rotation. Moreover, the thesis presents examples of derived detailed plasma information from MPR data such as the kinetic energy densities for the thermal and supra-thermal parts of the fuel ion population as well as the synergetic coupling of RF power to the fast ions from NB injection. The results constitute a stepping-stone for neutron emission spectroscopy as a main diagnostic for ITER and other future fusion experiments on thermonuclear ignition.</p>

High power fusion plasmas produced in the world’s largest facility for magnetic confinement experiments (JET), have been studied using the neutron emission measured with the magnetic proton recoil (MPR) spectrometer. The MPR has been used to observe plasmas since 1996 including those of deuterium-tritium leading to several fusion records and corresponding observational achievements of neutron emission spectroscopy. Noteworthy are novel studies of the complex states of fuel ions arising through plasma heating by neutral beam (NB) injection and radio frequency (RF) power. This thesis concerns the analysis of MPR data on the neutron emission from NB heated discharges alone and in combination with RF. A main objective of these studies has been the effect of supra-thermal fuel ion reactions on the fusion power as compared to the basic thermal component. The analysis was based on dedicated models to describe the velocity distributions of the ion population under the influence of the NB and RF heating in a parametric form allowing trial neutron spectra to be calculated and fitted to the data to select the kinetic state of the fuel ions that best described the MPR observations. Spectral signatures of different underlying plasma states and phenomena were identified and results from up to five different ion reaction contributions to the fusion power were demonstrated besides the global plasma features of toroidal rotation. Moreover, the thesis presents examples of derived detailed plasma information from MPR data such as the kinetic energy densities for the thermal and supra-thermal parts of the fuel ion population as well as the synergetic coupling of RF power to the fast ions from NB injection. The results constitute a stepping-stone for neutron emission spectroscopy as a main diagnostic for ITER and other future fusion experiments on thermonuclear ignition.

Indiana University-Purdue University Indianapolis (IUPUI) / Multiresolution image fusion is an emerging area of research for use in military and commercial applications. While many methods for image fusion have been developed, improvements can still be made. In many cases, image fusion methods are tailored to specific applications and are limited as a result. In order to make improvements to general image fusion, novel methods have been developed based on the wavelet transform and empirical variance. One particular novelty is the use of directional filtering in conjunction with wavelet transforms. Instead of treating the vertical, horizontal, and diagonal sub-bands of a wavelet transform the same, each sub-band is handled independently by applying custom filter windows. Results of the new methods exhibit better performance across a wide range of images highlighting different situations.