Energy distribution of the ternary alpha's emitted in 235U(nth, f) and 252Cf(SF)

Charged particles emitted in ternary fission appear to have a Gaussian-shaped energy distribution, except for the α particles, for which mostly an important non-Gaussian low-energy tailing is reported. We realised good experimental conditions for studying the 235U(nth, f) ternary α energy distribution at the reactor of the ILL in Grenoble. Thanks to an intense and clean neutron beam, a small, thin sample of highly enriched U could be used, with an activity of only 1.6 Bq, so the measurements could be done without absorber in between the sample and the detector. With the resulting low detection limit of 6 MeV, a clearly asymmetric energy distribution was obtained, deviating by 6% from a Gaussian shape. This energy distribution has been deconvoluted into components corresponding to “true” ternary α''s and α''s originating from the decay of 5He particles. Ternary α emission yield data have been re-evaluated accordingly. [Copyright &y& Elsevier]