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

摘要

Charged particles emitted in ternary fission appear to have a Gaussian-shaped energy distribution, except for the a particles, for which mostly an important non-Gaussian low-energy tailing is reported. We realised good experimental conditions for studying the U-235(n(th), f) ternary alpha 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 DeltaE-E 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 alpha's and alpha's originating from the decay of He-5 particles. Ternary a emission yield data have been re-evaluated accordingly. (C) 2004 Elsevier B.V. All rights reserved.