A Note on the Small-Angle Elastic Scattering of Fast Neutrons from C, N, and O.
BALLISTIC RESEARCH LABS ABERDEEN PROVING GROUND MD
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The calculation of neutron transport in air requires an accurate knowledge of the neutron cross sections for nitrogen and oxygen. Existing direct measurement of the total elastic cross section for nitrogen is in marked disagreement with the value deduced by taking the difference between the total cross section and the sum of all partial non-elastic cross sections. This discrepancy in the available data indicates an error in the total-elastic measurement of 30 or in the total non-elastic cross section of 50. A technique to measure differential cross sections for the small-angle 3 degrees to 15 degrees scattering of fast neutrons has been developed and applied to a study of the scattering of 7.55 and 9.5 MeV neutrons from N, O, and C. Preliminary analysis of measurements obtained thus far show that the forward angle elastic scattering in nitrogen theta 15 degrees has been underestimated in previous work and that the missing cross section should be assigned to the total elastic scattering cross section. Preliminary data obtained thus far for N, O, and C indicate that conventional extrapolation procedures which equate the zero degree scattering cross section to a minimum value given by Wicks Limit underestimate the magnitude of the forward scattering by as much as 30. Author
- Nuclear Radiation Shielding, Protection and Safety
- Nuclear Physics and Elementary Particle Physics