Fast neutron-induced fission cross section measurements for actinides and sub-actinides: results and experimental technique development
Alexander Laptev (Los Alamos National Laboratory)
This talk is a description of an experimental approach for fast neutron-induced fission cross section measurements of actinides and sub-actinides relevant for the nuclear fuel cycle. Two types of experiments are described, which use a parallel-plate fission ionization chamber and a time projection chamber (TPC). Observed parallel-plate fission ionization chamber experiments were done at the WNR and GNEIS facilities. The advantages and accuracy level of that experimental approach are discussed and obtained results are presented. A time projection chamber experiment is posed as a new step in experimental fission research aimed at improvement in accuracy level of measured cross sections. The TPC approach is based on highly pixelated readout anodes that allow 3D-reconstruction of tracks for all secondary particles from neutron-induced reactions. In return this eliminates many sources of systematic errors intrinsic to the parallel-plate fission chamber approach. The most important error source to remove is correctly identifying fission fragments from other types of events like alpha-particles, electronic noise, etc. There are also other sources of uncertainties, such as large uncertainties in existing data for angular anisotropy of fission fragments, efficiency, and competing nuclear reactions at high incident neutron energy that will be eliminated. Results of fission TPC commissioning at a fast neutron beam line of the LANSCE/WNR facility in the 2010-2012 beam campaigns will be presented.
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