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Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

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166 CHAPTER 5<br />

Figure 5-12. Measuring attenuation of gamma rays under conditions of good geometry. Ideally, the<br />

beam should be well collimated and the source should be as far away as possible from the detec<strong>to</strong>r;<br />

the absorber should be midway between the source and the detec<strong>to</strong>r and should be thin enough so<br />

that the likelihood of a second scattering of a pho<strong>to</strong>n already scattered by the absorber is negligible;<br />

and there should be no scattering material in the vicinity of the detec<strong>to</strong>r.<br />

Figure 5-13. Attenuation of gamma rays under conditions of good geometry. The solid lines are the<br />

attenuation curves for 0.662-MeV (monoenergetic) gamma rays. The dotted line is the attenuation<br />

curve for a heterochromatic beam.

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