Multiple coherent scattering of γ-radiation

Conclusions

Multiplying (5) by 2πϑdϑ and integrating over angle, we get the relationship between the total flux and depth in the form$\varphi (z) = e--\overline \mu z,$, where$\overline \mu = \mu - (\pi a/\eta ^2 ) = \mu - \mu _{coh} .$.

A similar result is obtained from integration of (11) over the angles and integration of (12) over the plane z = const. It thus follows that if we are interested in the angular distribution forϑ η in the first two cases and in the radial distribution forρ zη in the third case, we can make an approximate estimate of the coherent scattering by eliminating the appropriate term fromμ. This approach has been used in [15 etc.] but no indications were given of the conditions under which this is permissible.

For problems in which small angles or small distances from the axis of a collimated source are important, allowance for the coherent scattering can change the result by an order of magnitude or more. For angles ϑ η andϑžη it is possible to consider only the coherent scattering and to use (5), (11), and (12). For angles ϑ>gh and scatteringρ >ηz, the contribution from coherent and incoherent scattering can be comparable. The kinetic equation must then be solved with allowance for both effects.