Astronomical and cosmological observations reveal that the majority of the matter in our universe is made of an unknown, non-luminous substance called dark matter. Many experimental attempts are underway to directly detect particle dark matter, which is very difficult to measure due to the expected low interaction rate with normal matter. DEAP-3600 is a direct dark matter search experiment located two kilometres underground at SNOLAB, in Sudbury, Ontario. DEAP-3600 will make use of liquid argon as the detector material, which scintillates as charged particles pass through. The work presented here is an investigation of expected background sources in the DEAP detector. Because DEAP-3600 is a noble liquid-based experiment, a thin film of [1,1,4,4]-tetraphenyl-[1,3]-butadiene (TPB) is coated on the detector walls to shift the scintillation peak from the UV to visible regime for detection. However, alphas passing through TPB produce scintillation signals which can mimic recoil events. Because scintillation properties can change with temperature, we have conducted an investigation of alpha-induced TPB scintillation at temperatures ranging from 300 K to 3.4 K. We were able to characterize the light yield and decay times, and demonstrated that these background events should be distinguishable from true recoil events in liquid argon, thus enabling DEAP-3600 to achieve higher dark matter sensitivity. Additionally, we investigate the performance of the liquid argon purification systems, specifically the activated charcoal used for radon filtration. Previous measurements with the DEAP prototype experiment have demonstrated the necessity of removing radon from the argon prior to filling the detector, due to the release of contaminates from the argon storage systems. Charcoal radon filters are extremely efficient, however, if the emanation rate of the charcoal is too high, there is the possibility of re-contamination. We performed a measurement of the radon emanation rate of a charcoal sample using a radon emanation and extraction system at Queens University. We demonstrated that the emanation rate of the charcoal was consistent with zero. We also show that the number of residual radon atoms which reach the detector would not be an issue for DEAP-3600. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-10-10 18:36:40.2

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Various compounds were studied with solid-state 119Sn and 31P NMR spectroscopy and quantum chemical calculations. Connections were made between the shielding tensors and the geometric and electronic structures of the molecules. First, the 119Sn chemical shielding anisotropy of various para substituted tetraaryl tin compounds was shown to be dependent on the tilt angle of the phenyl rings. Tetrakis(o-tolyl) tin did not have the shielding anisotropy predicted by the tilt angle of the rings. It was suggested that ortho substitution distorts the structures of the phenyl rings causing the discrepancy. Analysis of the solid-state 31P NMR spectra of triphenylphosphorane ylides, Ph3P=CHC(O)R, determined that increasing the electron-donating effects of the R group decreased the δ33 component. Theoretical calculations showed that the component lay along the ylidic bond and was dependent on the difference in phosphorus-carbon bond lengths between the phenyl and ylidic bonds. Another study concerned the solid-state 31P NMR of the series of triphenylphosphine derivatives, PPh3-x(o-tolyl)x where x = 0 to 3. The addition of ortho methyl groups changed the position of the δ11 component which could be the result of the change in energy gap between the lone pair (HOMO) and σ* anti-bonding (LUMO). The solid-state 31P NMR spectra of deuterated piperazinium phosphonate and phosphonic acid were influenced by the shielding, dipolar and spin-spin interactions, as well as, second order quadrupolar effects. The spectrum of deuterated piperazinium phosphonate had a chemical shielding anisotropy of 130 ppm, an effective dipolar coupling of 2500 kHz and a one-bond phosphorus-deuterium J coupling of 90 Hz. The phosphorus-deuterium bond length was predicted to be 1.44(2) Å. A deuterium quadrupolar coupling constant of 104 kHz was obtained from the CP/MAS 2H spectrum. The non-axial symmetry of phosphonic acid complicated the analysis of the 31P spectrum. Phosphorus-deuterium bond lengths of 1.44(5) Å and 1.40(4) Å were obtained for the two inequivalent sites in the unit cell.