Quantitative measurement of small-angle gamma ray scattering from water, nylon, and Lucite

The small-angle (2 degrees-10 degrees) total-differential-scattering cross sections of water, methyl methacrylate, and nylon 6 have been measured at a photon energy of 59.54 keV. An annular target geometry has been used with an acceptance of +/- 0.5 degrees and an experimental uncertainty of approximately 4% achieved. The experimental methods and data corrections necessary to obtain this accuracy are discussed in detail. The results demonstrate clearly the contribution of intermolecular effects to the scattering process and allow critical comparison with calculations using molecular form factors for water obtained from interpolated x-ray diffractometer data; agreement is obtained within the experimental uncertainties. They also support earlier Monte Carlo predictions of scattering in water at angles of the order of 2 degrees which are in disagreement with certain published experimental data.