As a successor of the Sudbury Neutrino Observatory, the SNO+ experiment is planned to start data taking in early 2013. Making use of the liquid scintillator, Linear Alkylbenzene (LAB), the SNO+ experiment aims to perform ux measurements of low energy solar neutrinos in one phase, and wait for neutrinoless double beta decay events in another phase where 44 kg of natural Neodymium would be added into LAB. The Rayleigh ratio of LAB was found to be 16.60 _ 3.14 _10 6 cm 1 at 546 nm using the relative measurement technique. The wavelength dependency of the Rayleigh scattering was also examined and compared with the theoretical prediction. A setup which is usable to measure the angular dependency of the Rayleigh scattering was built, and an isotropic behaviour of the scattering was tested. The _ and backgrounds, due to the internal calibration ropes situated in the scintillator volume, were studied using the SNO+ Monte Carlo Package. Also, the amount of 210Pb originating from the internal calibration ropes due to the intrinsic contamination of 238U, Rn emanation and plated on the surface prior to the installation were assessed to examine if it is a tolerable level to achieve the target level of 13.4 background events per day. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-08-31 15:56:59.875

Radioactive isotopes are present at some level in all materials in our environment. Detection of these isotopes by conventional means can be difficult if they decay very slowly (have a long half-life). Accelerator Mass Spectrometry (AMS) systems are actually designed to measure extremely low levels or such isotopes. Such measurements are often useful for dating geological processes and archaeological artifacts or tracing chemical pathways through complex systems. In the search for very rare processes such as neutrinoless double beta decay, the presence of very low levels of radioactive material can interfere with the measurement process. Therefore, materials used to build the experimental equipment have to contain as few radioactive isotopes as possible. Neutrinoless double beta decay (NDBD) is of interest for understanding whether the neutrinos are Dirac or Majorana particles. SNO+ and nEXO are among the experiments at SNO Lab, located in Sudbury, Canada for the detection of neutrinos and other extremely weak physical processes. The SNO+ detector is a large 12m diameter spherical scintillation counter which will be able to study low energy solar, geo- and reactor neutrinos, as well as being able to conduct supernova searches. This detector was built with materials with very low radioactivity such as the organic liquid, Linear Alkyl Benzene (LAB), the scintillation fluid in which the radioactivity was measured in earlier scintillation detectors. For NSBD measurements, the SNO+ experiment will add tellurium-130 to the LAB; In order to fully mix the 130Te into the LAB, the liquid 1, 2 Butanediol has been selected as a chelating agent to which the atoms of 130Te can be added. This project describes the measurement of the 14C content of the 1, 2 Butanediol which confirmed its suitability for use in the NDBD experiment. nEXO is the next in a series of experiments dedicated to the search for NDBD in Xenon-136. The nEXO detector is a time projection chamber (TPC) filled with 5000 kg of liquid Xe. One major source of reduction in sensitivity of this detector is the radioactive decay of trace amounts of uranium and thorium isotopes naturally present the construction materials. In order to assess the quantity of these isotopes in the copper used to make the electrodes in the TPC, samples of the copper to be used in the chamber were analyzed using AMS. In this measurement, a better source of copper was found.

This work presents the calibration of the energy response of the Sudbury Neutrino Observatory (SNO). The development of the energy response processor RSP and its use in setting the energy scale of SNO and reconstructing the energy of neutrino-like events is presented for each of the three phases of SNO: the pure heavy water phase, the salt phase, and the neutral current detector (NCD) phase. A 16N calibration source, producing mainly 6.13 MeV γ-rays, is the primary energy calibration source. It is used to set the energy scale of the detector and to test for errors in the energy calibration and reconstruction process. The errors associated with energy reconstruction in the pure heavy water and salt phase data, that is to be used in a low energy threshold solar 8B neutrino analysis, are derived for the RSP energy response processor and shown to be in agreement with other analyses. The largest of the errors, that associated with using the 16N source to set the energy scale of the detector, is improved through a detailed and thorough analysis. The calibration of the energy scale of the photomultiplier tube array in the third phase, with an array of 3He proportional counters (NCDs) distributed within the heavy water, is presented. The event energy reconstruction errors in the NCD phase are reassessed with more precise measurements and shown to be in agreement with the conservative estimates used in the analysis SNO presented in 2008. The implications of the improvements in the error are assessed and the solar 8B neutrino fluxes—charged current (CC), elastic scattering (ES), and neutral current (NC)—are determined to be: φCC = 1.68+0.09−0.07, φES = 1.79+0.25-0.22, and φNC = 5.52+0.48-0.45, in units of 10^6/cm^2/s. The errors quoted are the combined statistical and systematic uncertainties. These results are in good agreement with the results published by SNO in 2008 with a modest improvement in the CC measurement. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-09-23 01:40:45.237

No description available.

The SNO+ experiment will use a liquid scintillator based detector to study solar, geo, and reactor neutrinos and double beta decay. This thesis discusses the effect of backgrounds on the measurement of neutrinoless double beta decay and describes analysis techniques developed to reduce their impact. Details of the modeling of the photomultiplier tubes in the SNO+ Monte Carlo RAT are first described and comparisons are made with the SNO Monte Carlo SNOMAN. SNOMAN has been extensively verified with calibration sources and RAT is shown to be in good agreement. The event reconstruction techniques are then presented and predict an achievable 15cm position and 7% energy resolution. The backgrounds are discussed and pileup backgrounds identified, including many previous unknown pileup backgrounds. Techniques to reject the pileup background are presented and shown to give over 99% rejection in the region of the double beta decay end point (3-4MeV), below the irreducible background from solar neutrinos. Finally the resulting limit on the effective Majorana neutrino mass SNO+ could achieve in 2015 is predicted to be 270meV and this is compared with other experiments that are underway.

Current requirements of nonvolatile memory (NVM) are the high density cells, low-power consumption, high-speed operation and good reliability for the scaling down devices. However, all of the charges stored in the floating gate will leak into the substrate if the tunnel oxide has a leakage path in the conventional NVMs. Therefore, the tunnel oxide thickness is difficult to scale down in terms of charge retention and endurance. The nanocrystal nonvolatile memories are one of promising substitution, because the discrete storage nodes as the charge storage media have been effectively improve data retention under endurance test for the scaling down device. Many methods have been developed recently for the formation of nanocrystals. Generally, most methods need thermal treatment with high temperature and long duration. This procedure will influence thermal budget and throughput in current manufacture technology of semiconductor industry. And supercritical carbon dioxide (SCCO2) has been researched to the passivation of dielectric and reducing the activation energy. The research estimates SCCO2 is potential to form nanocrystals for these reason. This research is to discuss the feasibility of fabricating nanocrystal NVMs device with low temperature SCCO2. The low melting point metal material Sn is used for the attempts. In order to check if Sn can be used for fabricating nanocrystal NVMs device, the research selects the conventional thermal annealing method first. It uses rapid thermal annealing to improve the crystalline of nanocrystals and reliability of the memory device. Compare to different Sn containment or chemistry and different process, analyze the electric characteristics and materials chemistry. At last, select the Sn and SiO2 co-sputtering film to try the SCCO2 process and analyze these characteristics as well. Due to the novel technology, many physical mechanism and improvement of properties will be discuss following.

This thesis consists of two parts; the first part pertains to fractoluminescence as a potential background in crystal scintillator detectors, and the second part bears on the simulation of a 24Na source to be used during the liquid scintillator phase of the SNO+ experiment. I participated in early work to develop a test-bed to study fractoluminescence in scintillators, and report here on preliminary results I obtained before I shifted my focus to SNO+. Full results obtained by the group have since been reported in PRL 111 154301 [1]. This project follows the discovery that mechanical stress on a dark matter detector’s crystals was causing a background signal. The response of inorganic crystal scintillators (Bi4Ge3O12, ZnWO4 , CdWO4 ) compressed to the point of rupture was studied. The double cleavage drilled compression geometry was used to create controlled cracks in 20×5×3 mm3 samples. A correlation between a sudden drop of the force, a burst of photonic and of acoustic emissions was discovered and a lower bound was set on the conversion efficiency from strain energy to light energy. SNO+ is a large underground experiment that aims primarily to search for neutrinoless double beta decay. The SNO+ detector consists of an acrylic vessel of liquid scintillator surrounded by light detectors. A tagged 24Na source was proposed as one of several radioactive sources to be deployed within the vessel to calibrate the detector. To achieve this an activated NaI(Tl) crystal would be coupled to a photomultiplier tube and lowered into the center of the vessel. The second half of this thesis explores options for implementing this plan and presents the detector response to a 24Na source as simulated by the Monte Carlo software developed by SNO+. The size of the crystal influences the type of information that can be gleaned from using this source so four different crystal sizes are presented for comparison. The simulations show that the source can be used to test the linearity of the energy scale and the simulation’s quenching model. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-06-18 17:46:15.685

Oxide semiconductors have been envisaged to find applications in ubiquitous flexible electronics in daily life such as wearable electronic gadgets to offer novel user experiences. However, one of the bottlenecks to realise these applications is a lack of oxide-semiconductor components capable of wireless communications. As Bluetooth and Wi-Fi are the two dominant communication interfaces, fast enough front-end rectifiers must be developed to operate at their gigahertz (GHz) transmission frequencies. Furthermore, despite of significant developments of n-type oxide semiconductors in the last decade, widespread flexible electronics also requires high-performance p-type oxide semiconductors for use in complementary logic circuits. The objectives of this dissertation are to develop high quality Schottky barriers, achieve GHz speed Schottky diodes on rigid and flexible substrates, evaluate the noise properties of the Schottky diodes, develop p-type oxide semiconductor using sputtering technology, elucidate the hole transport mechanism in p type transistors, and demonstrate their potential applications such as radio receivers, complementary inverters and ring oscillators. First, indium gallium zinc oxide (IGZO) Schottky diodes were fabricated by using radio frequency magnetron sputtering. The oxygen content at the metal-IGZO interface was found to have a profound effect on the electrical performance. By introducing 3% O2 during the deposition of Pt or IGZO, the diodes exhibited excellent electrical properties without requiring any annealing treatment, thus allowing for the realisation of flexible IGZO Schottky diodes. The high-frequency properties of Pt-IGZO Schottky diodes on glass substrates were optimised by testing a range of IGZO thicknesses and diode active areas. The achieved highest cut-off frequency was beyond 20 GHz, which is to the best of our knowledge the fastest oxide-semiconductor device to date. On flexible substrates, the diodes also showed cut-off frequencies up to 6.3 GHz, well beyond the critical benchmark speed of 2.45 GHz for typical wireless communications. In order to assess the feasibility of using IGZO Schottky diodes in practical applications, measurements were taken to discern their low-frequency noise properties. In the as-deposited diodes, logarithmic dependence of the noise spectral density on the applied bias was observed, revealing that the dominant noise was generated in the space-charge region at low biases and in the series-resistance region at high biases, respectively. After annealing the diodes, very different noise mechanism was observed and the interface-trap-induced noise dominated the noise spectra. As one of the most promising p-type oxide semiconductors, SnO was also studied at low temperatures in this thesis. The experiment revealed that hole-transport mechanism was governed by either band conduction or variable range hopping in different temperature ranges. Finally, the potential for fully oxide-based electronics was demonstrated by an amplitude-modulation radio receiver comprising of an IGZO Schottky diode as the demodulator and a complementary ring oscillator based on IGZO and SnO transistors. In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of the University of Manchester's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.

The starting SNO+ experiment, successor to the Sudbury Neutrino Observatory, is a neutrino detector using LAB based liquid scintillator as active medium. Situated in the SNOLab deep underground laboratory in Sudbury, Canada, the rock overburden amounts to about 6 km.w.e., providing an effective shielding against cosmic rays. The residual muon rate is 63 μ/day going through the detector volume. About 780 t of an LAB mixture inside an acrylic sphere with a 6 m radius will be observed by ≈ 9300 photomultipliers, surrounded by a ≈ 7000 t water shielding. SNO+ will be searching for low energy solar-, geo-, reactor- and supernova neutrinos, but the main goal is the observation of the neutrinoless double beta decay in Te-130. Under operating conditions, the scintillator will be cooled to about 12° C. This work investigated the effect of temperature changes on the light output of LAB based liquid scintillator in a range from -5° C to 30° C with α-particles and electrons in a small scale setup. Assuming a linear behaviour, a combined negative temperature coefficient of (−0.29 ± 0.01) %/° C is found. Considering hints for a particle type dependency, electrons show (−0.17 ± 0.02) %/° C whereas the temperature dependency seems stronger for α-particles (−0.35 ± 0.03) %/° C. A pulse shape analysis shows increased strength of a slow decay component at lower temperatures, pointing to reduced non-radiative triplet state de-excitations at lower temperatures. Furthermore, this work found upper bounds for the in-situ muon-induced isotope production via scaling calculations and simulations with Geant4 based software. For the most concerning isotope C-11, an upper limit of about 1.3 × 10^3 decays/kt/yr is found and a reduction technique, developed by the Borexino collaboration, can be effectively applied for SNO+. Also a muon reconstruction algorithm is implemented, performing reasonably well, but not good enough to improve the background reduction scheme. / Das zukünftige SNO+ experiment, Nachfolger des Sudbury Neutrino Observatory, ist ein Neutrino-Detektor mit LAB basierten Flüssigszintillator als aktivem Medium. Im SNOLab Untertagelabor (Sudbury, Kanada) gelegen, ist es durch die Felsüberdeckung von 6 km.w.e. hervorragend gegen kosmische Strahlung abgeschirmt. Die Rate der übrigen Myonen die das Detektorvolumen durchdringen beträgt ca. 63 μ/Tag. In einer Acrylkugel, mit einem Radius von 6 m, wird eine LAB Mischung von ≈ 9300 Photomultipliern beobachtet und von einer Wasserabschirmung von ≈ 7 kt umgeben. SNO+ wird nach niederenergetischen solaren-, Geo-, Reaktor- und Supernova Neutrinos suchen, aber das Hauptziel ist die Beobachtung von neutrinolosen doppelten Betazerfällen in Te-130. Unter den Betriebsbedingungen wird der Flüssigszintillator eine Temperatur von ca. 12° C annehmen. Diese Arbeit hat den Einfluss von Temperaturveränderungen in einem Bereich von -5° C to 30° C auf die erzeugte Lichtmenge untersucht. Dazu wurden α-Teilchen und Elektronen in einem kleineren Versuchaufbau beobachtet. Unter der Annahme eines linearen Verhaltens, wurde ein globaler negativer Temperaturkoeffizient von (−0.29 ± 0.01) %/° C gefunden. Unter Berücksichtigung von Hinweisen auf eine Teilchenartabhängigkeit, findet sich für Elektronen ein Koeffizient von (−0.17 ± 0.02) %/° C, wohingegen α-Teilchen eine stärkere Abhängikeit von (−0.35 ± 0.03) %/° C aufweisen. Eine Pulsformanalyse zeigt eine bei tieferen Temperaturen stärker ausgeprägte langsame Zerfallskomponente, was darauf hinweist dass die nicht-radiativen Abregungen der Triplet-Zustände bei niedrigeren Temperaturen reduziert sind. Weiterhin wurden in dieser Arbeit obere Ausschlußgrenzen für in-situ Myon-induzierte Isotopenproduktion gefunden, wozu Skalierungsrechnungen und Simulation mit auf Geant4 basierender Software benutzt wurden. Für das wichtigste Isotop C-11 wurde eine obere Grenze von 1.3 × 10^3 Ereignisse/kt/Jahr gefunden und eine Technik zur Reduzierung des Untergrundes, entwickelt von der Borexino Kollaboration, kann effektiv für SNO+ angewendet werden. Darüber hinaus wurde eine Myon Spurrekonstruktion implementiert, die sinnvolle Ergebnisse liefert, aber nicht gut genug ist um die Untergrund Reduzierung zu unterstützen.

Made available in DSpace on 2016-08-19T12:56:43Z (GMT). No. of bitstreams: 1 Dissertacao Wanderson.pdf: 6558678 bytes, checksum: 6817981e9e9dda09b67fbeb466f7115a (MD5) Previous issue date: 2013-02-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The ethanol oxidation reaction was investigated using on line differential electrochemical mass spectrometry (DEMS) on carbon-supported Pt-SnO2 electrocatalysts at atomic ratio 1:1, 2:1 and 3:1 as a function of ethanol concentration and combined analysis of the reaction products and electrochemical measurements. The materials were prepared by two methods: impregnation/thermal decomposition with and without chemical reduction via sodium borohydride. They were characterized by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) techniques. A comparative study showed that the second method was more efficient to synthesize of these materials, which were chosen for DEMS and electrochemistry studies. Electrochemical measurements showed better faradaic current in lower potentials, indicating better activity to ethanol oxidation on PtSnO₂/C, Pt₂SnO₂/C and Pt₃SnO₂/C catalysts compared to Pt/C E-TEK. Pt/C E-TEK presented the best ratio between the CO₂ and acetaldehyde production in 0.01 mol Lˉ¹ ethanol, showing that this electrode favors the reaction via CO₂ production. When the ethanol concentration is increased, the ratio CO₂ /acetaldehyde decreases for all catalysts studied, mainly for Pt/C E-TEK. This increasing formation of acetaldehyde was largely responsible for the profile of faradaic currents in view of the onset for the formation of acetaldehyde to coincide with the beginning of the ethanol oxidation reaction. In general, the catalysts based on Pt-SnO₂ showed better performances for the ethanol reaction compared to Pt/C E-TEK, thus confirming the ability of SnO₂ to provide oxygen species for oxidize adsorbed intermediates such as CHx and OHads, at lower potentials. / A reação de oxidação de etanol foi investigada usando a espectrometria de massas eletroquímica diferencial on line (DEMS), sobre eletrocatalisadores de Pt-SnO₂ suportados em carbono Vulcan, com razão atômica 1:1, 2:1 e 3:1 em função da concentração de etanol e análises combinadas dos produtos reacionais e medidas de corrente eletroquímica. Os materiais foram preparados por dois métodos: impregnação/decomposição térmica com e sem redução química via borohidreto de sódio. Eles foram caracterizados pelas técnicas de energia dispersiva de raios X (EDX) e difratometria de raios X (DRX). Um estudo comparativo mostrou que o segundo método foi mais eficiente na síntese desses materiais, sendo escolhido para os estudos eletroquímicos e de DEMS. As medidas eletroquímicas mostraram melhores correntes faradáicas em menores potencias, indicando melhor atividade para a oxidação de etanol sobre os catalisadores PtSnO₂/C, Pt₂SnO₂/C e Pt₃SnO₂/C comparado com Pt/C E-TEK. A Pt/C E-TEK apresentou a melhor razão entre CO₂ e acetaldeído em etanol 0,01 mol Lˉ¹, mostrando que esse eletrodo favorece a via de formação de CO₂. Quando a concentração de etanol é aumentada, a razão CO₂/acetaldeído diminui para todos os catalisadores estudados, principalmente Pt/C E-TEK. Esse aumento na formação de acetaldeído foi o grande responsável pelo perfil de corrente faradáica, tendo em vista o início da reação de formação do acetaldeído coincidir com o início da reação de oxidação de etanol. Em geral, os catalisadores à base de Pt-SnO₂ apresentaram melhor desempenho para a reação de oxidação de etanol em relação a Pt/C E-TEK, confirmando assim a capacidade do SnO₂ em fornecer espécies oxigenadas para oxidar intermediários adsorvidos tais como CHx e OHads, em potenciais mais baixos.