Graduate Thesis Or Dissertation
 

Measurement of environmental gamma exposure by thermoluminescence dosimetry

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/hm50tv644

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  • Energy dependence, angular dependence, and linearity of response to exposure levels were studied for the thermoluminescent dosimeter used in an environmental monitoring network. The dosimeter consisted of a manganese activated calcium fluoride phosphor (Ca F₂: Mn) bonded to a helical heating element and encapsulated in a gas filled glass tube. Energy dependence was studied using a K-alpha, K-beta x-ray fluorescence system which produced energies from 6.47 keV to 100.96 keV. The response to ¹³⁷ Cs and ⁶⁰ Co gamma was also tested. The curve generated by the data may be useful to correct dosimeter readings when the energy of the radiation is known. Angular dependence at 662 keV produced a 20 percent drop in response for radiation parallel to the dosimeter axis compared to the most sensitive incident angle of 90° . For exposures between 10 mR and 1 R the response of the dosimeter was linear within ± 5 percent, however for exposures greater than 1 R, there was an over-response which increased with exposure. When the reader was adjusted to read correctly at 100 mR, the response to 3000 R, the highest exposure given, was 32 percent high. For the conditions usually encountered in environmental monitoring, the dosimeter can be used with no more than a simple calibration correction. If, on the other hand, low energy radiation, very directional beams, or high exposures are encountered, further corrections may be necessary.
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file details FitzsimmonsCharles1971.pdf 2017-08-14 Pubblico Scaricare