Fragment Energy and Velocity Measurements in Fission of Uranium by 2.9-GeV Protons

Fission of uranium induced by 2.9-GeV protons was studied with semiconductor detectors and velocity-measuring devices. The angular correlation between members of fission-fragment pairs as well as the energies of the two fragments and the velocities of one were determined. Fragment masses were thus ascertained. From these data, deductions were made about excitation energies and momenta of the fissioning systems. The results show that although there is a much broader mass spectrum of fissioning nuclei produced at 2.9 GeV than is present at lower bombarding energies, the fission mechanisms in the two cases are indistinguishable. Mean fragment velocities are found to be very nearly independent of fissioning-system mass, in agreement with calculations based on a liquid-drop model.