The Sudbury Neutrino Observatory (SNO) was a 1 kilotonne heavy water Č{C}erenkov detector. Evidence for flavour changing neutrino oscillations was found by comparing the rate of Charged Current interactions with that of Neutral Current (NC) interactions. This thesis is concerned with the accurate determination of the NC flux in the Neutral Current Detector (NCD) phase of SNO. The measurement and understanding of radioactive backgrounds arising from decays of naturally occurring $^{232}$Th and $^{238}$U chain nuclei is crucial. This is because their daughter nuclei can produce neutrons via photodisintegration of deuterium. These would be indistinguishable from those produced by NC neutrino interactions. As the probability of neutron production was dependent upon the nature and location of activity, each contribution had to be determined separately. Of particular concern were $^{232}$Th and $^{238}$U in the D$_2$O and Neutral Current Detectors (NCDs). A maximum likelihood method was developed that exploited differences in the event isotropy and radial profile of each event class. These results were in agreement with water assay results and pre-deployment radioassays of the NCDs. An independent measurement of the $^{232}$Th content in the D$_2$O and H$_2$O was made by regularly assaying the water using filters loaded with hydrous titanium oxide. The concentration of $^{232}$Th in the water was determined by coincidence counting of the final assay sample. A new counter system was designed and built and the calibration and use of this system are presented. Two areas of increased activity were discovered on two of the NCDs deployed in the detector which would have prevented an accurate measurement of the NC flux. A method was devised to determine the composition and activity of one of these hotspots. The results were in good agreement with two independent methods and the uncertainty on the NC flux was reduced from $>7$% to $<1$%. The total number of neutrons produced per day by photodisintegration for $^{232}$Th and $^{238}$U in the D$_2$O and NCDs was measured to be $0.66^{+0.08}_{-0.07}$. This was significantly less than the expected 12.6 NC neutrino interactions per day. In the third phase, two independent data streams existed: PMT and NCD. A Monte Carlo study was undertaken to determine whether an accurate measure of the NC flux could be obtained using only PMT data. Results showed that no improvement could be made upon results from previous phases and the best measurement of the NC flux in the final phase would be made using PMT and NCD data.

This diploma thesis deals with particle detectors and their use. In the introduction the reader becomes familiar with concepts of radioactivity and radiation. Next part tells the reader how nuclear radiation penetrates through matter and how this is used for particle detection. Next part presents utilizing radiation in nuclear medicine and medical imaging. The main part of this work concentrates on the design and preparation of an original high school experiment. Here the aim of this experiment is described and its design and implementation is documented. Last part brings the description of technical solutions used, steering computer program developed for this experiment and results of tests.

Nuclear magnetic resonance (NMR) of small samples and nuclei with a low gyromagnetic ratio is intrinsically insensitive due to the received signal dependence on Boltzmann's statistics. This insensitivity can be partially overcome through the application of hyper polarisation techniques such as Dissolution Dynamic Nuclear Polarisation (D-DNP). It is hoped that the hyper polarised 13C signal received from labelled small molecules could facilitate imaging of metabolic and transporter processes in biological systems. In order to realise this, appropriate molecules and experimental hardware must be used. A detailed description of the experimental set-up used for carrying out DDNP is given and the system is characterised. the advantageous use of a dual iso-centre magnet system is elucidated with optimisation of acquisition of fast relaxing molecules. such a system allows for interrogation of processes with short relaxation times, not possible with traditional, stand-alone polarisers. To acquire the maximum amount of hyper-polarised 13C signal in an imaging experiment, parallel acquisition techniques have been implemented and the hardware designed with such goals in mind. Multiple coils have been used to allow accelerated image acquisition. As such this work has validated the SENSE algorithm for artefact free, image reconstruction on the micro-scale. These techniques require an array of coils which add to the complexity of the design of the probehead. Decoupling methods and array coil construction must be considered the methods used to ensure well isolated coils, such as geometric decoupling, are presented. The novel fabrication and implementation of micro-coils for imaging and spectroscopy of nL scale samples is presented this will help facilitate the acquisition of images showing metabolic processes in active transport in cells. By placing the coils close to the sample it is possible to gain sensitivity relative to the mass of the sample in question. To achieve signal detection on the order of nL a novel, exible micro-coil array has been fabricated and the results of NMR experiments carried out on both protons and 13C are shown. This is the final stage before integrating the coils with the D-DNP system. The acquisition of 13C signal with the micro-coils displays optimal electronic characteristics when compared with other detectors presented in the literature. The final goal of the work is to produce a system that is capable of micro imaging in small biological samples such as the Xenopus Oocyte with a view to monitoring metabolic processes and transportation without the need for the use of the large fluorescing proteins (GFP's) that have been used in previous work (1). The need for GFP's attached to metabolites results in the measured data being non-physical as the fluorescing protein is often much larger than the molecule being transported. It is hoped that the use of hyperpolarised small molecules (such as pyruvic acid) may be able to remove this need for GFP's in the study of metabolite transportation.

Although NMR is a versatile technique, the low values associated with nuclear spin polarization provide inherently weak signals. A novel system to perform temperature-jump dynamic nuclear polarization (DNP) has been designed and developed at the University of Nottingham, with the aim to enhance this signal and improve the sensitivity of the NMR experiment. This system utilizes a bespoke helium flow cryostat, located within the bore of a superconducting magnet, to achieve temperatures down to 1.75 K for high levels of polarization to build up on an electron spin population. This high level of polarization can then be transferred to a nuclear species of interest using microwave irradiation, while remaining at low temperature, allowing the weak signals associated with NMR to become enhanced. Following ample nuclear polarization build-up, a powerful mid-IR laser is used to rapidly bring the sample to 300 K, ensuring the spectra benefit from the line narrowing associated with liquid-state NMR. An Er:YAG laser with a wavelength of 2.94 μm has been chosen for this as it couples energy directly into the vibrational modes of hydroxyl groups present within the sample. The rapid heating mechanism underpins the success of this experiment twofold. Firstly, performing the temperature-jump in a shorter time period preserves a greater signal enhancement. This needs to be done carefully as too much heating will obliterate the sample, destroying the signal. Secondly, a temperature-jump without dilution of the sample, as occurs in dissolution DNP, allows sample recycling to take place. This opens the technique up for otherwise unavailable applications, such as multidimensional correlation spectroscopy with repetitive excitations. Development of the cryo-system, heating mechanism and NMR probe, alongside preliminary experiments and calculations, suggest that this technique should greatly improve the sensitivity of the liquid state NMR experiment.

Airborne dusts can transport radioactive materials in the form of isolated individual radioactively-hot particles containing high concentrations of radioisotopes. These airborne particles may be inhaled or ingested, becoming a source of internal radiation exposure. After the March 11, 2011, nuclear reactor accidents at Fukushima Daiichi, in northern Japan; eighty-five Japanese environmental samples and 234 US and Canadian samples were collected and analyzed by gamma spectrometry, autoradiography, scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDS), and total alpha and beta counts. Social media and volunteer organizations were an important part of the sample collection effort. The combination of autoradiography and SEM/EDS allowed individual radioactively-hot particles to be isolated and analyzed. Detectable levels of 134Cs and 137Cs were found in 62 of 85 Japanese particulate matter samples. The median dust specific activity for Japanese samples was 2.5 Bq g-1 +/- 1.6 Bq g-1, while the mean dust specific activity was 71 Bq g-1 (RSD = 335 %). The mean was skewed high due to five dust samples with sharply higher specific activities. These five samples had specific activities ranging from 167 kBq g-1 to 5.2 PBq kg-1. Only four of 234 US and Canadian environmental samples had detectable levels of both 134Cs and 137Cs. Gross gamma spectroscopy of Japanese samples also detected 131I and 60Co. US and Canadian dust samples showed primarily naturally-occurring nuclides. More than 300 individual hot particles were identified in Japanese samples. The Japanese particles analyzed by SEM/EDS were found to contain cesium, americium, radium, polonium, tellurium, rubidium and other necessarily or potentially radioactive elements. No cesium-containing hot particles were found in the US, however some dust particles were found that contained uranium, thorium and plutonium. These US particles were all related to identified uranium mines or nuclear materials storage and processing sites. Some of the hot particles detected in this study could cause significant radiation exposures to individuals if inhaled. Where hot particles are present in the environment, radiation dose models must include this exposure component to remain accurate.

No description available.

The ultra-strong magnetic fields of magnetars have profound implications for their radiative phenomena. We study the dynamics of strong magnetic fields inside and outside magnetars. Inside the magnetar, the strong magnetic stress can break the crust and trigger plastic failures. The interaction between magnetic fields and plastic failures is studied in two scenarios: 1. Internal Hall waves launched from the core-crust interface can initiate plastic failures and lead to X-ray outbursts. 2. External Alfven waves produced by giant flares can also initiate crustal plastic failures which dissipate the waves and give rise to delayed thermal afterglow. The crustal dissipation of Alfven waves competes with the magnetospheric dissipation outside the magnetar. Using a high order simulation of Force-Free Electrodynamics (FFE), we found that the magnetospheric dissipation of Alfven waves is generally slow and most wave energy will dissipate inside the magnetar.

Graduation date: 1966

Graduation date: 1966

In situ salinity, turbidity and temperature were measured at discrete depths and water samples for radioanalysis were simultaneously collected in the Columbia River Estuary using a specially designed instrument package. Particulate radioactivity was concentrated by filtration and the dissolved radioactivity by evaporation or ferric oxide bulk precipitation. Radioanalysis was by gamma-ray spectrometry and data reduction by computer. Chromium-51 was mostly dissolved and conservative in brackish water, while zinc-65 was mostly particulate and non-conservative. The intrusion of salt water into the estuary was seen to greatly increase the concentrations of particulate chromium-51, zinc-65 and scandium-46 near the bottom. The fall and rise in estuarine radioactivity levels were followed during an infrequent pause in Hanford reactor operations. Changes in radioactivity levels of up to three orders of magnitude were recorded at Astoria, Oregon, some 380 miles from the reactors. The pause in reactor operations enabled the determination of river flow times from the reactors to Astoria. Flow times of 12 and 19 days were measured for average river discharges of 290,000 and 130,000 c.f.s., respectively. / Graduation date: 1967