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Directional correlation from oriented states and linear poralization measurements of Gamma Rays from 190T1.Madiba, Tshifhiwa Elmon. January 2008 (has links)
<p>High-spin states in the oblate deformed odd-odd thallium nucleus ( ) 109 190 81 Tl have been investigated through the reaction 175Lu(20Ne, 5n)190Tl at a beam energy of 115 MeV. The gamma rays emitted from 190Tl nucleus were detected with Ge detectors using the AFRODITE array at iThemba LABS, South Africa. Gamma-gamma coincidence data were obtained and used to construct the level scheme. In this work, Directional Correlations from Oriented (DCO) state ratios and linear polarization anisotropies were measured in order to deduce spin and parity of energy levels in the decay scheme. It was possible to determine the spin and parity of two additional signature-partner bands which decay to the ground-state band.</p>
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Photon flux monitor for a mono-energetic gamma ray sourceMavrichi, Octavian 25 March 2010
A novel photon flux monitor has been designed and tested for use at the Duke University High Intensity Gamma Source, where the photon beam produced is essentially mono-energetic but it is not tagged. Direct counting of the number of photons using a high-efficiency detector is not possible because of the high photon fluxes expected. Therefore, a direct counting detector with a low, accurately known efficiency was required.<p>
The photon flux monitor based on a five scintillator paddle system detects recoil electrons and positrons from photoelectric, Compton and pair-production processes. It has been designed to be insensitive to gain and detector threshold changes and to be usable for photon energies above 5 MeV. It has been calibrated using direct counting with a NaI detector and its efficiency has been shown to be well predicted by a GEANT4 simulation.<p>
Results of measurements, calibration and calculations required to characterize the 5-paddle photon flux monitor are presented. The photon flux monitor has met its design specifications of being able to determine the number of photons incident on it during the live time of a measurement to within a systematic error of 2%.<p>
A paper based on the work for this thesis has been published in the Nuclear Instruments and Methods in Physics Research Journal.
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Photon flux monitor for a mono-energetic gamma ray sourceMavrichi, Octavian 25 March 2010 (has links)
A novel photon flux monitor has been designed and tested for use at the Duke University High Intensity Gamma Source, where the photon beam produced is essentially mono-energetic but it is not tagged. Direct counting of the number of photons using a high-efficiency detector is not possible because of the high photon fluxes expected. Therefore, a direct counting detector with a low, accurately known efficiency was required.<p>
The photon flux monitor based on a five scintillator paddle system detects recoil electrons and positrons from photoelectric, Compton and pair-production processes. It has been designed to be insensitive to gain and detector threshold changes and to be usable for photon energies above 5 MeV. It has been calibrated using direct counting with a NaI detector and its efficiency has been shown to be well predicted by a GEANT4 simulation.<p>
Results of measurements, calibration and calculations required to characterize the 5-paddle photon flux monitor are presented. The photon flux monitor has met its design specifications of being able to determine the number of photons incident on it during the live time of a measurement to within a systematic error of 2%.<p>
A paper based on the work for this thesis has been published in the Nuclear Instruments and Methods in Physics Research Journal.
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DESIGN AND CONSTRUCTION OF A MODULAR GAMMA CAMERA (NUCLEAR)Milster, Thomas Dean, 1958- January 1987 (has links)
The Anger camera has been used for the last quarter century in many areas of science to image gamma radiation. Some typical applications include medicine, where functionality of organs are studied in vivo, and industrial inspection of fuel rods for nuclear reactors. The standard Anger geometry includes a large scintillation crystal, light guide, photomultiplier array, and analog processing electronics. Even the most modern gamma cameras built today still use the standard Anger design. The work presented here describes an alternative to the standard gamma-camera design that is flexible enough to be used in a wide variety of applications. Especially in single-photon emmission computed tomography (SPECT) applications, the new design has the potential to be more efficient than the standard design. The new design is modular, that is, several small, separate units comprise a system. Each unit consists of a small gamma camera that is optically and electronically independent from other units. The units, called "modular cameras," can be configured around the region of interest so as to provide the maximum amount of information for reconstruction algorithms or direct information to the operator. The theoretical and experimental investigation of this report focuses on the design and construction of the modular cameras. Each modular camera is, in esscence, a small Anger camera. Components of each module include a scintillation crystal, a light guide, and an array of four photomultiplier tubes. Instead of an analog processing network, each module utilizes fast digital circuitry which includes direct analog-to-digital conversion of the photomultiplier signals, a lookup table which maps detector responses to position estimates of the scintillation flashes in the crystal, and an image memory which accumulates the position estimates and forms an image of the radiation incident on the faceplate of the camera. The digital electronics are necessary because analog techniques fail to give satisfactory estimates of scintillation position when the flashes occur near the sides of the crystal. The contents of the lookup table are determined from the statistical properties of the detected signals as a function of scintillation position. Experiments are described in which "best" estimates of position are found by processing data collected from an array of point-source positions in contact with the crystal. Alternative methods for construction of the lookup table are also discussed, which involve computer generation of the estimates. Both maximum-likelihood and mimimum-mean-square-error estimation rules are used, and the results are compared. A mathematical bound on the performance of the estimators is calculated assuming Poisson statistics for the detection process. The bound, which is a Cramer-Rao lower bound, is used to compare module geometries before lookup tables are constructed. A one-dimensional module, which accumulates information along one axis of the faceplate, is designed first. The one-dimensional module provides proof-of-principle evidence for the estimation techniques and is used to determine critical parameters for modular-camera design. The results of the experiments with the one-dimensional camera are extended to two-dimensional designs, which yield position estimates along both axes of the camera faceplate. Several two-dimensional cameras are tested, and an optimum geometry is constructed and tested for spatial resolution and bias of the estimators.
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Beta-gamma directional correlation in Eu[superscript152] and Eu[superscript154]Dulaney, Harry Gingles 05 1900 (has links)
No description available.
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The decay of Ir^;p192^;sShiel, Vincent Wymore 05 1900 (has links)
No description available.
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Directional correlation from oriented states and linear poralization measurements of Gamma Rays from 190T1.Madiba, Tshifhiwa Elmon. January 2008 (has links)
<p>High-spin states in the oblate deformed odd-odd thallium nucleus ( ) 109 190 81 Tl have been investigated through the reaction 175Lu(20Ne, 5n)190Tl at a beam energy of 115 MeV. The gamma rays emitted from 190Tl nucleus were detected with Ge detectors using the AFRODITE array at iThemba LABS, South Africa. Gamma-gamma coincidence data were obtained and used to construct the level scheme. In this work, Directional Correlations from Oriented (DCO) state ratios and linear polarization anisotropies were measured in order to deduce spin and parity of energy levels in the decay scheme. It was possible to determine the spin and parity of two additional signature-partner bands which decay to the ground-state band.</p>
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Critical assessment of the MEDUSA gamma ray detection system for radon flux measurement on a tailings dam / Tebogo Gladys Kgaugelo MotlhabaneMotlhabane, Tebogo Gladys Kgaugelo January 2003 (has links)
Worldwide measurement of radon flux on mine tailing dams has been performed
using various instruments. Some of the methods used in South Africa are electrets,
alpha tracks, accumulator cans etc. Although these techniques and methods have
been used for many years, a number of shortcomings are still evident. The major
shortcomings are that, the methods lack spatial representivity that is, they only
measure the radon flux at a point where they' are placed and not the whole site in that
way, the spatial variation is not shown in a site which is not homogeneous. Another
shortcoming is that, they do not show seasonal variation and some have a back
diffusion problem, and the time required for the result to be known is too long. For·
example it takes several days for electrets to gather sufficient information required,
yet it is a single point result. This makes it difficult to steer the measurement.
Furthermore, the moisture and atmospheric pressure on the mine dump influence
some of the measurements.
The above shortcomings led to the investigation of a new· technique based on
gamma ray spectrometry to quantitatively assess the radon flux from the mine
tailings dam. The system is called Multi Element Detector for Underwater Sediment
Activity (MEDUSA). Initially, this technique was uniquely designed to measure the
radioactivity on the sea floor where it proved to be successful. The major focus of
this research study was, therefore, to critically assess the MEDUSA gamma ray
detector system for measurement of radon flux on a tailings dam.
The process of determining the radon flux in this work involved field measurements
using MEDUSA and laboratory measurements using Hyper Pure Germanium (HPGe}
detector. The laboratory measurements were for correcting the field measurements.
The HPGe has better advantage over MEDUSA in terms of resolution and this
means that the gamma ray energy peaks have better visibility than on the MEDUSA.
The field measurements on the tailings dam were done using the MEDUSA mounted
on a 4x4 vehicle, and simultaneously sample points were identified and samples
collected.
The samples were measured for specific activity in the laboratory using gamma
spectrometer with HPGe detector. These measurements enabled the determination
of a factor that was used to calculate the activity of radium in the field. This activity
was found to have an average of 309 Bq.kg"1 with data range of 60 -540 Bq.kg-1.A radon flux equation was then derived and used to calculate the radon flux on the field. Based on the radium content, the radon flux was calculated to average about 0.105 ± 0.023 Bq.m-2 .s-1
The results are within the same range as the previous flux measurement on the
same tailings dam but with better statistics. This research work has demonstrated
that the MEDUSA can be adapted for radon flux determination from tailings dam. The
method promises to address some of the key shortcomings of existing techniques
and the usefulness of this method can be extended to measuring radioactivity on
contaminated sites for rehabilitation purposes. / Thesis (MSc. ARST) North-West University, Mafikeng Campus, 2003
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A search for very high energy gamma-rays from Hercules X-1 using the pulse profile technique / by Michael Damien Roberts.Roberts, Michael Damien January 1993 (has links)
Errata inserted inside back cover. / Bibliography: p. 155-162. / vii, 162 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1994
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Use of BC-523a liquid scintillator for simultaneous neutron spectroscopy and gamma counting with the implementation of a neutron history reconstruction algorithm /Frey, Wesley D. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 86-90). Also available on the World Wide Web.
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