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Fission 233U(n,f)

The work performed at CENBG took place in a revaluation campaign of the fission cross-section ^{233}U(n,f) in the range of fast neutrons (1-6.5 MeV). It is possible to measure this cross-section from the number of detected fission fragments, the neutron flux incident on the target and the number of target nuclei.

  • Fission fragments were detected by 2 photovoltaic cells.
  • The number of target nuclei was determined from the number of α particles from the ^{233}U decay measured with a Si detector.
  • The estimation of the neutron flux is the most delicate measurement, the neutron flux can be deducted from the activity of monitoring targets (such as gold foils, fission rate of ^{235}U), or from the elastic scattering (n,p) of neutrons by a polypropylene film of several microns in thickness. It was this latest method that was used since the (n,p) scattering cross-section is known with a much higher precision (1%) than for the other above-mentioned reactions. The protons were detected with a Si surface barrier detector.