Reactions of Cesium with 240-Mev Protons

Absolute yields of radionuclides produced in the spallation of cesium with 240-Mev protons have been measured from barium to ruthenium. The yields are based on the known cross section for the monitor reaction ${\mathrm{Al}}^{27}(p, 3pn){\mathrm{Na}}^{24}$. In agreement with the well-established pattern for high-energy spallation yields, the results indicate that the majority of reactions occur as primary knock-on collisions in which the incident proton interacts with only a few nucleons. This primary interaction is followed by a dissipation of the residual nuclear excitation, whose energy spread is very broad, leading to a distribution of products which reach far down the nuclide chart.