No description available.

No description available.

A new beta-ray detector using the Thick Gas Electron Multiplier (THGEM) technology is presented. Traditional proportional counters have been considered the standard for many decades for radiation contamination monitoring. However, it has always been challenging to detect low energy beta-emitters such as 3H and 14C. In order to extend the low energy cut-off of these beta particles, it is important to keep the electron multiplication gain as high as possible. To accomplish this goal, we have developed a new gaseous beta-ray detector using THGEMs. Founded on previous THGEM avalanche simulations [1] and predecessor detectors, a novel prototype THGEM beta-ray detector was designed and fabricated. Its signal performance, effective gain and gain stability were comprehensively studied for single and double-THGEM configurations using an alpha source. The first time THGEM detector response to beta-rays was observed for various operating conditions and compared with Monte Carlo N-Particle Transport 6 (MCNP6) Monte Carlo simulations. / Thesis / Master of Science (MSc)

Radioimmunotherapy consists in the use of beta radioactive labeled monoclonal antibodies as selective carriers of radiation to tumors. Internal spatially distributed sources created at the disease sites would deliver high radiation doses to tumors while the normal tissues would not be exposed to the intense radiation as in conventional forms of cancer treatments. A rapid and accurate estimation of the spatial dose distribution from nonuniform sources is essential for the optimization of this form of cancer therapy. The method used for such calculations is based on the knowledge of dose distributions around a unit source, quantities referred to as dose kernels. Thus far, the Monte Carlo technique is the most accurate way of the dose kernel determinations. However, for routine dosimetry simpler and less time consuming methods of adequate accuracy may appear more preferable. The "scaling factor" method is used to determine the depth dose distribution in a medium based on data about the dose distribution in an arbitrary reference medium (e.g. air, water). The transformation of the dose distribution curves from the reference medium to the desired new medium is done using a constant, known as scaling factor or relative dose attenuation, and a closely related renormalization factor imposed by the energy conservation. This work investigates the accuracy of the scaling factor method using a statistical approach (generalized chi-squared test), focusing on a particular case of potential practical interest, the scaling factor water to bone. The work also investigates a procedure for extending the applicability of the scaling factor method to dosimetry in dissimilar media, as a first step, a planar interface. / Thesis / Master of Science (MS)

The purpose of this research was to develop and test a radiation detector to perform beta dosimetry and spectroscopy. The detector utilizes plastic scintillator volumes to produce scintillation light in proportion to the amount of energy deposited in them, and a large-area avalanche photodiode to convert the light to electrical signals. Pulse processing electronics transform the electrical signals into a format useful for analysis, and various software programs are used to analyze the resulting data. The detector proved capable of measuring dose, as compared to Monte Carlo n-Particle simulations, to within about 50% or better, depending on geometry and source type. Spectroscopy results, in conjunction with MCNP-based spectral enhancement methods, proved the detector capable of recording beta spectra with endpoint energies greater than about 250 keV. The detector shows promise for further development as a portable beta detector for field use in beta-contaminated areas. / Graduation date: 2005

Missing page viii. Page 171 was repeated with different text. / <p> The decay of 14.9 min. ⁸⁹Rb to levels in ⁸⁹Sr has been studied by use of Ge(Li) detectors, NaI(Tl) detectors and a magnetic beta ray spectrometer. Fourteen gamma rays have been studied by ɣ-ɣ and β-ɣ coincidence experiments and establish levels at 0, 1.031, 2,000, 2.277, 2.567, 2.708, 2.770, 3.225 and 3.500 MeV. The Q value is 4.486 ± .012 Mev. </p> <p> The techniques of beta and gamma ray spectroscopy using Ge(Li), NaI(Tl) and plastic beta detectors have been applied in the study of the decay of 3.2 min. ⁸⁹Kr to levels in ⁸⁹Rb. Seventy nine of the one hundred and eleven observed gamma rays have been classified in the proposed decay scheme. The Q value is 5.15 ± .03 MeV. </p> / Thesis / Doctor of Philosophy (PhD)