An Experimental re-evaluation of Photon Mass Attenuation Coefficients

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Date
2013-03-28Author
Crewson, Cody
Type
ThesisDegree Level
MastersMetadata
Show full item recordAbstract
Photon mass attenuation coefficients are indispensable input parameters for use in several disciplines. They are of value for medical diagnostics, radiation therapy, material science, etc. Currently, photon mass attenuation coefficients derived from model calculations are widely used. This project directly measured the photon mass attenuation coefficients of water and a number of water based solutions. These measurements were made using a High Purity Germanium (HPGe) detector allowing for increased resolution beyond traditional techniques. Four sources were used (\Ba, \Eu, \Cs, \Am) producing multiple photons of interest over the range of 40 keV to 1.4 MeV, allowed for simultaneous collection of data and a refining of uncertainties beyond past techniques. Direct measurements using a new liquid technique supported the validity of Bragg's additive law, allowing for the mass attenuation coefficient of a constituent element to be calculated from a set of independent measurements. This technique allows materials not easily directly measured to be determined without an overburdening increase in uncertainty. The same direct measurements showed a deviation from the currently relied upon National Institute of Standards and Technology (NIST) database - XCOM. Investigations of the deviation and surrounding references showed XCOM being at most accurate to 5 \% relative uncertainty.
Degree
Master of Science (M.Sc.)Department
Physics and Engineering PhysicsProgram
PhysicsSupervisor
Rangacharyulu, CharyCommittee
Hirose, Akira; Pywell, Rob; Deters, Ralph; Xiao, ChijinCopyright Date
February 2013Subject
physics
gamma radiation
attenuation coefficients
compton scattering
photo-electric effect