Energy Dependence of Proton-Proton Scattering, 18.8 to 31.8 Mev

Measurements have been made of the absolute differential cross section of proton-proton scattering at 90^∘{} in the center-of-mass system. The energy of the incident protons was varied from 31.8 Mev down to 18.8 Mev, and an energy interval of ±{}1.0 percent was selected by means of a deflecting magnet. Apparatus using a proportional counter and a triple coincidence method was used to reduce the background. Measurements were made simultaneously, using apparatus for measuring the angular distribution at 31.8 Mev and a single charge integrator for collecting the incident proton beam.The cross section at 90^∘{} in the center-of-mass system varies approximately as the reciprocal of the energy of the incident protons over the range investigated. Data are presented to show this dependence. Comparison is made with a Yukawa potential well, and with the tensor model selected by Christian and Noyes.