Placzek corrections

A Placzek correction to remove the inelastic efiects has been performed by fitting a pol5momial (9) to the higher range of q linearly weighting the data to account for the higher effect at higher values of q. 

The inelasticity correction, or Placzek correction as it is often known [37], compensates for the static assumption introduced earlier. As with the multiple scattering correction the derivation is beyond the scope of this work however the important point is that the magnitude of the correction is minimal for heavy nuclei and high incident energies [48]. It should be mentioned that the Placzek correction is strongly dependent on the energy dependence of the detector efficiency. 

It is worthwhile to remark that pile radius R and rod radius r are effective radii . They denote the radii at which the thermal neutron density, if extrapolated from the pile, would become zero. This is particularly important as far as the rod radius vq is concerned. As Placzek and Seidel have shown (MT-5) the thermal neutron density does not vanish at the surface of an absorbing rod but obeys the condition n< =. 710A dn /dr where A is the mean free path. It should be remembered, however, that even with this correction, the whole treatment becomes invalid if ro is small as compared with the mean free path. 

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