A computer code was written to calculate elastic scattering cross sections using the Klein-Gordon equation. The reason for writing this code is because existing codes do not include relativistic kinematics and therefore are only valid for lower energies. This code was used to analyze alpha particle and pion scattering at relativistic energies upon different target nuclei and to find a relativistic potential for a system at a given energy. The target particles in the alpha study were 12C, 40,42,44,48Ca and other alphas. The pions were incident upon 12C and 40Ca. Optical potentials of different forms were used to compare with previous analyses and the experimental data. The potentials found in this study could be useful to understand the physics underlying other processes such as inelastic and particle transfer reactions. The computer code can be used to extend elastic scattering calculations to angles where data does not exist which can then be compared to future experiments. The code could also be used to create a database of potentials for several systems to study the effects of changing charge, mass or energy of the system.

We present an ultra-thin transmission-type radiation detector developed for counting microbeam alpha particles. The ∆E alpha detector is a single crystal chemical vapor deposited diamond (ScCVDD) and will be installed between the microbeam accelerator window and a biologic sample. The commercially available optical grade ScCVDD sample (3 mm × 3 mm × 50 µm) was etched down to a few µm thickness which allows alpha particles to penetrate, and then it was followed by the surface cleaning, electrical contact deposition and post-metallization annealing. SRIM code and MCNP6 were used for energy loss calculation of alpha particles in electrodes and diamond and pulse height spectra prediction. In order to evaluate the performance of the ultra-thin ScCVDD detector, a ∆E-E detectors system was setup using a calibration source, the ScCVD detector and a silicon surface barrier detector (SBD). The absolute and intrinsic totally efficiency were determined as 0.3 % and 16 % respectively. Alpha and gamma peaks were observed while the peak resolution is not quite promised. The transmission ability of the ScCVDD detector was verified by applying coincidence operation with 0.22 µs time window. The thickness of the ultra-thin diamond sample was reassessed to be 8.315±0.690 µm from ∆E-E spectrometery. / Thesis / Master of Science (MSc)

Both animal and human studies suggest that cognitive bias toward negative information, such as that observed in major depression, may arise through the interaction of cortisol (CORT) and norepinephrine (NE) within the amygdala. To date, there is no published account of the relationship between endogenous NE and CORT levels and cognitive bias. The present study examined salivary CORT and salivary alpha-amylase (sAA), an indirect measure of NE, in relation to masked affective priming of words in young female participants. Women with higher salivary CORT showed increased priming to negative word pairs only when sAA was also high; when sAA was low, no effect of CORT on priming was observed. These results are in line with previous research indicating that increased CORT is linked to enhanced processing of negative information. However, our findings extend this literature in providing evidence that CORT predicts enhanced processing of negatively valenced information only in the presence of higher sAA.

<p> The alpha-activity of natural samarium has been studied using an ionization chamber. A gridless ionization chamber has been developed in order to obtain high resolution and high sensitivity. The half lives and the energies of the alpha decay of Sm147 and Sm148 were measured where as the alpha-activity of Sm149 and Sm146 could not be detected.</p> <p> Experiments were carried out in order to search for the existence of Particle stable neutron clusters in the range of Mass 6-10 as a component of a nuclear reactor flux and as the product of high energy proton spallation of heavy nuclei.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The combined capabilities of alpha-particle emitting isotopic excitation sources and modern semiconductor detectors are investigated with a view to extending the light-element range of radioisotope-based X-ray emission analysis.</p> <p> The construction and performance of a windowless low-energy X-ray spectrometer designed around a lithium-drifted silicon detector and a 210Po source are discussed. It is shown that under the conditions used low-energy X-ray emission and detection are greatly favoured.</p> <p> Measurements of relative cross-sections for the production of X-rays by ~5.2 MeV alpha-particles in elements from oxygen to iron are reported. The results for elements of Z>16 are in good agreement with those predicted from the scaling of equal velocity proton values but show large positive deviations for elements of Z<16.</p> <p> Investigative applications of the spectrometer to quantitative analyses of blast-furnace slags, iron ores and silicate rocks for oxygen, silicon, sulpher, calcium and iron are described.</p> <p> The future prospects of radioisotopic alpha-particle X-ray excitation methods are surveyed.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The alpha decay properties of nuclei decaying across the N = 126 closed neutron configuration are examined. A systematic occurrence of isomerism is esteblished in the odd-odd N = 2.27 isotones from a detailed study of 214Fr and 216Ac. Energy level spacings of the odd-odd N = 125 isotones 208Bi, 210At, and 212Fr are found to exhibit a distinct· correspondence. The Mang shell model theory of alpha decay is evoked to explain the reduced width fluctuations of the even-odd N = 127 isotones. Theoretical and experimental results are also presented for the alpha decay of 215Ra. The new isotopes 222Th , 221Th , 218Ra, and . 217R a are synthesized and studied. Precise atomic masses are calculated for several nuclei from the measurement of alpha decay Q-values. </p> / Thesis / Doctor of Philosophy (PhD)

Over the last two decades there has been an increased interest in understanding the influence of trace boron additions in Ti alloys. These additions refine the prior β grain size in as-cast Ti alloys along with increasing their modulus and yield strength due to the precipitation of TiB. TiB also acts as a heterogeneous nucleation site for α precipitation and has been shown to influence the α phase morphology. B is completely soluble in liquid Ti but has a negligible solubility in both body centered cubic β and hexagonal close packed α phases of Ti. Thus, during solidification of hypoeutectic B containing alloys, B is rejected from β into the liquid where it reacts with Ti to form pristine single crystal whiskers of TiB. Despite a substantial amount of reported experimental work on the characterization of TiB precipitates, its formation mechanism and influence on α phase precipitation are still not clear. The current work is divided into two parts – (i) understanding the mechanism of TiB formation using first principles based density functional theory (DFT) calculations and (ii) elucidating how TiB influences the α phase morphology and crystallography in titanium alloys using electron microscopy techniques. TiB exhibits anisotropic growth morphology with [010] direction as its predominant growth direction and displays a hexagonal cross section with (100), (101), and (10) as the bounding planes. A high density of stacking faults has been experimentally observed on the (100) plane. The present study, by using DFT based nudged elastic band (NEB) calculations, elucidates for the first time that the diffusion of B through TiB is via an interstitial-assisted mechanism as opposed to vacancy-assisted mechanism hypothesized in literature. This one dimensional interstitial-assisted diffusion results in the anisotropic growth of TiB. In addition, the energetics of TiB- α interfaces was calculated to understand the hexagonal cross-section of TiB. The intimate mixing of B27 and Bf structures and their co-existence with stacking faults has been explained by calculating the interfacial energy of B27/Bf interfaces along with stacking fault formation energy. The boride precipitates have also been shown to modify the morphology of α phase from lath like to more equiaxed like. However, the influence of TiB on the crystallography of α precipitation has not been explored in great detail. The present study will clearly demonstrate, for the first time, the influence of various alloying elements present in the titanium alloy, on the resulting effect of B addition on α morphology and its crystallography in Ti alloys. Thus, the influence of B addition on α precipitation in two classes of commercial Ti alloys, i.e. β alloys and α + β alloys have been explored. It has been found that TiB nucleated α can either become equiaxed by a loss of Burgers orientation relationship (OR) with β or can retain the lath morphology in case of alloys containing a combination of Ti, Al and Mo.

In this Thesis we present a description of α cluster nuclei, in particular focusing on the case of 9 Be, with αn and αα interactions derived from Cluster Effective Field Theory (EFT). The two-body potentials are regularized by a Gaussian cutoff which cures the short-distance dependence of the interaction and the potential parameters are found comparing the effective range expansion (ERE) with the calculated T-matrix. The calculation of the ground-state energies is carried out by diagonalizing the Hamiltonian on a Non symmetryzed Hyperspherical Harmonics basis in momentum space. Using only two body interactions a rather strong cutoff dependence appears. However, we are able to reproduce the experimental ground-state energies for selected cutoff values for most of the studied nuclei. The strong cutoff dependence indicates the lack of three-body forces, therefore we extend our Cluster EFT approach by including such many-body forces. Finally, the 9Be photoabsorption cross-section is studied via the Lorentz integral transform method (LIT), focusing on the low-energy resonances coming from the electric dipole transitions. By fine tuning the parameters of the three-body force, we are able to reproduce, up to 4 MeV, the considered experimental resonances. For the description of the spectrum at higher energies the inclusion of the αα D-wave potential seems to be necessary.

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No description available.