For high-resolution X-ray imaging scintillator applications, we have prepared and optically characterized divalent samarium doped fluorochlorozirconate (FCZ:Sm2+) glasses and glass-ceramics. Sm2+ doped FCZ glasses were obtained by adding a reducing agent, NaBH4 into the initial melt to convert some of the Sm3+ to Sm2+. However, the Sm2+ concentration at most was estimated to be only approximately 0.003 %. The as-prepared glass samples were further heat treated to obtain glass-ceramics; the nucleation and growth of BaCl2 nanocrystals were confirmed by powdered X-ray diffraction (XRD) experiments. Depending on the heat treatment conditions (temperature and time), the average nanocrystal size varies from 8 to 170 nm, and the sample contains BaCl2 nanocrystals with the orthorhombic and/or hexagonal structure. The optical absorption spectra for our glass-ceramic samples suggested the substitution of Sm2+ ions into the BaCl2 lattice site. The FCZ:Sm2+ glass-ceramics samples showed strong fluorescence in the red region of spectrum (approximately 8 times that of an as-prepared glass), and the transparency can be very high (transmittance > 80 % for samples with thickness about 0.5 mm) and can be equivalent to that of an as-prepared glass . These two results promise potential as a high-resolution X-ray scintillator due to the emission wavelength range and high transparency. Extensive studies of photoluminescence (PL) spectra at low temperatures (12 -- 200 K) for FCZ:Sm2+ glass-ceramics suggested useful indicators of the crystal structure and average size of embedded BaCl2 nanocrystals. A detailed analysis of the optical spectra has lead to the identification of the origin of the emission peaks and the location of Sm ions at specific crystallographic sites. X-ray induced luminescence (XL) studies have suggested a strong dependence of the fluorescence intensity on the concentration of Sm2+ ions. In addition, for more efficient fluorescence, a sample should be heat treated in a hydrogen containing atmosphere (e.g. H2 + Ar gas), and the heat treatment conditions should be such that the nanocrystals grow in the hexagonal structure.

A two-scintillator paddle muon telescope with variable angular acceptance at the earth's surface was used to study correlations between flux distribution and barometric pressure. The detector was placed in 2 different locations around Georgia State University with varying paddle separations of 0, 7, and 14 inches. Correlation and anti-correlation analyses were conducted by using the muon count from the detector along with the barometric pressure, surface temperature, stratospheric temperature and solar activity. It was observed that there was a short and long-term variation relationship between cosmic ray counts and barometric pressure and also cosmic ray counts and temperature. No significant relationship was found between cosmic ray flux and solar activity. A new two-scintillator paddle telescope with larger detecting area was constructed in order to observe a stronger correlation between cosmic ray flux and pressure.

For high-resolution X-ray imaging scintillator applications, we have prepared and optically characterized divalent samarium doped fluorochlorozirconate (FCZ:Sm2+) glasses and glass-ceramics. Sm2+ doped FCZ glasses were obtained by adding a reducing agent, NaBH4 into the initial melt to convert some of the Sm3+ to Sm2+. However, the Sm2+ concentration at most was estimated to be only approximately 0.003 %. The as-prepared glass samples were further heat treated to obtain glass-ceramics; the nucleation and growth of BaCl2 nanocrystals were confirmed by powdered X-ray diffraction (XRD) experiments. Depending on the heat treatment conditions (temperature and time), the average nanocrystal size varies from 8 to 170 nm, and the sample contains BaCl2 nanocrystals with the orthorhombic and/or hexagonal structure. The optical absorption spectra for our glass-ceramic samples suggested the substitution of Sm2+ ions into the BaCl2 lattice site. The FCZ:Sm2+ glass-ceramics samples showed strong fluorescence in the red region of spectrum (approximately 8 times that of an as-prepared glass), and the transparency can be very high (transmittance > 80 % for samples with thickness about 0.5 mm) and can be equivalent to that of an as-prepared glass . These two results promise potential as a high-resolution X-ray scintillator due to the emission wavelength range and high transparency. Extensive studies of photoluminescence (PL) spectra at low temperatures (12 -- 200 K) for FCZ:Sm2+ glass-ceramics suggested useful indicators of the crystal structure and average size of embedded BaCl2 nanocrystals. A detailed analysis of the optical spectra has lead to the identification of the origin of the emission peaks and the location of Sm ions at specific crystallographic sites. X-ray induced luminescence (XL) studies have suggested a strong dependence of the fluorescence intensity on the concentration of Sm2+ ions. In addition, for more efficient fluorescence, a sample should be heat treated in a hydrogen containing atmosphere (e.g. H2 + Ar gas), and the heat treatment conditions should be such that the nanocrystals grow in the hexagonal structure.

Single crystals with composition Lu3Al5O12 were synthesized using Czochralski and micro-pulling-down melt growth techniques. Polycrystalline ceramics of the same composition were synthesized by vacuum annealing of powders prereacted using a citrate-nitrate combustion technique and by spark-plasma-sintering of powders prereacted using a flame-spray-pyrolysis technique. Single crystals and polycrystalline ceramics are activated with Ce3+ or Pr3+ or doubly activated with Ce3+ and Tb3+ ions. Cerium-doped Czochralski-grown single crystals were compared to cerium-terbium codoped Czochralski-grown and micro-pulling down single crystals. Cerium-terbium codoped single crystals are also compared to similarly-activated polycrystalline ceramics sintered under vacuum using combustion-synthesized prereacted powders. X-ray diffraction analysis and fluorescence characterization were used to determine successful formation of single-phase LuAG and successful incorporation of doping species. Absorbance, fluorescence, radioluminescence, and scintillation decay analyses were used to compare synthesis processes and activator selection.

The SNO+ experiment will be the SNO detector filled with a neodymium-loaded liquid scintillator instead of heavy water. SNO+ will be used to detect neutrinos of much lower energy. Also, SNO+ will conduct a search for neutrinoless double beta decay with Nd-150. The Nd-loaded scintillator in SNO+ will be made from linear alkylbenzene (LAB). Both the LAB solvent and the Nd loading are new developments. The optical properties of this scintillator and information about radioactive backgrounds should be studied. A calibration source known as the scintillator bucket was deployed in the water-filled SNO detector in order to study some optical properties of Nd-loaded scintillator, raw LAB scintillator and distilled LAB scintillator. Using a neutron source attached to the bucket to produce events with known energy, with a model of the scintillator bucket simulated by an analysis tool called RAT, the light yield of the scintillator could be determined by comparing data measurements with simulations. This allowed the light yield, one of the main optical properties of the scintillator, to be measured and that value to be corrected in the Monte Carlo. The bucket was deployed both at the centre of the detector and at the bottom. After subtracting backgrounds from radon introduced in the scintillator during preparation and filling, constraints on the amount of Po-210 were obtained. Estimates on the K-40 content of the Nd-loaded scintillator were obtained by analyzing the radon-subtracted background spectra. By comparing the background spectra with the bucket deployed at the bottom of the acrylic vessel with spectra from the bucket at the centre, it was possible to estimate the K-40 content of the acrylic vessel. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-09-22 11:55:44.351

The two-photon decay in nuclei has been formally theorized for many years and attempted to be measured on numerous occasions. The special case of a 0 + → 0 + transition in nuclei was examined for certain isotopes, and a branching ratio for the two-photon decay determined for each isotopes. Measurements of the branching ratio in nuclei other than this special case had so far proven unsuccessful. Motivated to find the two-photon branching ratio in a case where the transition competes with the single photon transition, we study the 11/2 − 137 Ba isomer. The experiment was performed at the Technische Universität Darmstadt using the available LaBr 3 scintillation detectors. We first study the absorption of various gamma energies by lead and compare the resulting values to a GEANT4 simulation. With an ideal value for lead shield thickness, the experimental setup is built in order to obtain a high two-photon count rate, while suppressing direct Compton scattering between detector pairs and suppressing other background interference. In order to suppress the background, plastic scintillators were placed atop the experimental setup. To treat the daunting level of random coincidences measured with this setup, fine energy and time gates were placed on the processed events in order to limit observation to the region of interest. Throughout the experiment, three different detector pair angles were successfully examined: 72 ◦ , 120 ◦ , and 144 ◦ . With these three angles a partial representation of the angular distribution of the two-photon decay is observed. The branching ratios were measured to be 1.56(23)·10 −6 , 0.55(22)·10 −6 , and 0.70(18)·10 −6 for the angles of 72 ◦ , 120 ◦ , and 144 ◦ respectively, with the values of 72 ◦ and 144 ◦ recorded in Ref.[1]. This experiment therefore shows it is possible to obtain a value for the two-photon branching ratio in the 11/2 − excited state of 137 Ba . A precise determination of this value, and for that of other nuclei, might contribute to solve current fundamental open problems such as restricting the parameters of the equation of state, or accurately determining neutron skin thickness.

The presented thesis focused on the study of a new material concept of Ce3+ doped multicom- ponent aluminum garnets (GdLu)3(GaAl)5O12. High purity single crystalline epitaxial films were grown by the method of liquid phase epitaxy from the BaO-B2O3-BaF2 flux with spe- cial emphasis on the elimination of the potential impurities coming from the flux. Combined experimental study of photoelectron yield (under alpha excitation), decay kinetics of fast and delayed recombination in the milisecond time range (under e-beam excitation) and photo-, cathodo- and radio-luminescence spectroscopies were used to characterize the studied mater- ial. The single-step nonradiative energy transfer from the donor Gd3+ to an acceptor Ce3+ was observed in the low Gd, Ce doped LuAG films and established as long-range dipole - dipole interaction. Special attention was devoted to the positive effect of combined Gd and Ga substitution on the extensive suppression of shallow traps, which are responsible for the slow component in the scintillation response. The best obtained scintillation characteristics of the studied epitaxial films were comparable with the top performance bulk crystals. 1

A scintillating optical fiber sensor of this work consists of a scintillating optical fiber, connected to a photomultiplier tube (PMT) via a conventional silica optical fiber. When a gamma ray impinges on the scintillating optical fiber, photons are generated inside the fiber. The photons are trapped inside the fiber and guided through the PMT. The PMT output signal is acquired by a computer. Two types of scintillating optical fibers sensors were developed for gamma ray detection. The first one is a silica optical fiber doped with an inorganic scintillating agent. The second one is a liquid core waveguide optical fiber filled with a solution of a nanostructured core shell CdSe/ZnS quantum dot. Test results indicate that the scintillating optical fibers developed in this work are sensitive for detecting gamma radiation. These scintillating fibers offer more flexibility for applications in nuclear energy industry as well as in nuclear medical research.

No description available.

This thesis presents the design qualification and construction of the Beam Scintillator Counter (BSC) for the CMS Collaboration at CERN in 2007 - 2008. The BSC detector is designed to aid in the commissioning of the Compact Muon Solenoid (CMS) during the first 2 years of operation and provide technical triggering for beam halo and minimum-bias events. Using plastic scintillator tiles mounted at both ends of CMS, it will detect minimum ionizing particles through the low-to-mid luminosity phases of the Large Hadron Collider (LHC) commissioning. During these early phases, the BSC will provide probably the most interesting and widely used data of any of the CMS sub-detectors and will be employed in the track based alignment procedure of the central tracker and commissioning of the Forward Hadron Calorimeter.