Measurement Of The Neutron Proton Cross Section At 10 Mev And 25 Mev

Neutron-proton scattering with 90 Mev neutrons has been investigated by others,1,2 using a proportional counter technique and also using a cloud chamber. They measured the scattering cross section for neutrons for center of mass angles from 36° to 180°. The present experiment was performed with nuclear emulsions in order to permit the detection of protons down to about 1.5 Mev, and to avoid systematic errors that might be present in the case of other methods of detection. The results agree with those of Hadley, et al., within probable error, and the cross section curve exhibits beyond 36° the same general trend as the curve measured by hadle, et al. The measurements confirm the fact that there is probably not complete symmetry of the n-p cross section curve about 90° in the center of the mass system.

The measurement of 28O-Mev neutron cross sections of various nuclei is described. The neutron beam used results from 340-Mev protons in the 184-in. cyclotron striking a 2-in. Be target. The neutron detector consists of a double coincidence anthracene scintillation counter telescope which counts recoil protons scattered at 15 deg from a paraffin cylinder placed in the collimated neutron beam. A 2-in. Cu absorber placed between the counters assures that only protons of energy greater than 250 Mev are counted. The cross sections for all nuclei measured from Li to Pb are smaller than the corresponding cross sections measured at 90 Mev by factors between 0.5 and 0.6.