233U and 235U thermal neutron fission accompanied by α particle emission at small angles to the fission axis

The thermal neutron fission of 233U and 235U is studied under the same experimental conditions. The fission acts accompanied by α particles outgoing at small angles with respect to the fission axis (sup(1/2)=15 deg) are studied. For each event the kinetic energies of both fragments and the α-particle energy have been measured. Mass distributions of fragments and the mass dependence of their mean kinetic energy are obtained. It is found that the small angle α-particle yield is proportional to the triple (but not double) fission probability. The available data are used to draw a conclusion that the α particles observed at the angles THETA approximately 0 deg are emitted from the space between fragments similarly to the α particles observed at theta approximately 90 deg