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Abstract

A measurement of fission fragment energy and mass distribution in the 239Pu(n,f) resolved resonance region has been performed at the IRMM, Geel, Belgium, making use of the twin Frisch-gridded ionization chamber technique. The challenging problem imposed by the strong á background was solved by developing an improved pile-up rejection system. The results for the mass and total kinetic energy (TKE) distributions for resolved resonance have been unexpected. Unlike it was the case for 235U(n,f) in the same energy region, no strong fluctuations have been observed for the mass and TKE distributions. In fact such fluctuations have been expected for the fission fragment properties, because the only possible low-energy spin states (Jð = 0+, 1+) belong to two well-separated (about 1.25 MeV) transition state bands. Neither spin dependence nor a dependence on Vp or 1/Ãf has been found in the energy region above 1 eV. The only exception might be the resonance at 0.3 eV.

Additional information

Authors: BAX H, JRC, IRMM (Institute for Reference, Materials and Measurements, Retieseweg, B-2440 Geel, (BE);DEMATTE L, JRC, IRMM (Institute for Reference, Materials and Measurements, Retieseweg, B-2440 Geel, (BE);HAMBSCH F.J, JRC, IRMM (Institute for Reference, Materials and Measurements, Retieseweg, B-2440 Geel, (BE)
Bibliographic Reference: Oral delivery given at: XV-th International Workshop on Fission Physics. Organised by: Institute of Physics and Power Engineering (IPPE) Obninsk in collaborations with MINATOR. Held in: Obninsk, Russia 2-6 October, 2000
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