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Correlation between the Build-up Factor, the g-ray Energy and the Effective Atomic Number in Open-Angle Measurements |
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PP: 73-80 |
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Author(s) |
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A.H. El-Kateb,
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Abstract |
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| The spectra of g-rays attenuated by soil, water, sand and cement in a broad beam geometry have been measured and analyzed at the energies 0.662 MeV from 137Cs and 1.173, 1.333 MeV from 60Co. The ratios of the photopeak to four main portions of the spectra were analyzed as a function of the material effective atomic number Zeff and the g-ray energy. The broad beam mass attenuation coefficients μb/ρ were compared with the theoretical values μ/ρ as a function of the effective atomic number Zeff and g-ray energy. The photopeak ratios have maximum values for photons scattered in the forward directions and decrease gradually for larger scattering angles. An inversion trend IT (maximum intensity build-up) in the peak ratios as a function of g-ray energy holds, in agreement with earlier results, where a decrease at the energy region 0.662 to 1.173 MeV changes to an increase at the energy region 1.173 to 1.332 MeV. These trends vanish gradually at larger scattering angles. The build-up factor B decreases with increase in the g-ray energy. Correlation between the build-up factor B and each of the effective atomic number Zeff and the g-ray energy was registered and discussed. Extensive attention to preparing collimated beam to measure μ/ρ might be saved if the measurement is performed under the conditions of minimum build-up factor B (maximum photopeak ratios). |
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