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Theses and Dissertations

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Browsing Theses and Dissertations by Subject "absorbed dose"

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    Characterization of mixed linear energy transfer environments utilizing tissue-equivalent proportional counters
    (Colorado State University. Libraries, 2023) Fehrman, Joseph M., author; Brandl, Alexander, advisor; Johnson, Thomas, advisor; Carlson, Kenneth, committee member
    There is currently great interest in the biological impact of radiological space exposures due to manned space missions (e.g., moon) where astronauts will face the challenge of living on board spacecraft for long periods of time. Cosmic radiation of many types exists in space and creates a unique mixed linear energy transfer (LET) environment. A tissue equivalent proportional counter (TEPC) was used to produce dose-equivalent measurements and quantify neutron exposures. Three neutron sources were used to simulate high energy, mixed LET environments: californium-252, a plutonium-beryllium source, and a deuterium-tritium neutron generator. TEPC dose-equivalent measurements can be utilized for basic research, and regulatory or clinical purposes for correlation with observable health effects. The main study was to quantify and compare TEPC dose equivalent rates in microdosimetric volumes to determine if significant dosimetric differences exist between mixed LET environments generated by photons and neutrons. The findings from this experiment showed that mixed LET environments where both photons and neutrons interacted with the TEPC had lower average LET values than neutron-only exposures, and produced varying dose equivalent rates that were dependent on the source characteristics. In summary, the TEPC was capable of monitoring in a mixed-LET environment and was successful at measuring the absorbed dose of high-energy photon and neutron interactions in space-like settings.