Absolute cross section measurements of neutron-induced fission of ${}^{242}\mathrm{Pu}$ from 1 to 2.5 MeV

The absolute neutron-induced fission cross section of ${}^{242}\mathrm{Pu}$ was measured at five energies between 1 and 2.5 MeV at the low-scatter neutron measurement facility of the National Physical Laboratory, UK. The measurements are part of an effort to reduce uncertainties of nuclear data related to fast spectrum reactors. The neutron-induced fission results are in good agreement with the Evaluated Nuclear Data File/B-VII.1 but disagree with several recent measurements near the resonance-like structure around 1.1 MeV. Within the same experimental campaign, the spontaneous fission half-life of ${}^{242}\mathrm{Pu}$ was measured and it is in good agreement with previous results.

Figure 1

Schematic drawing of the ionization chamber, beam line, and neutron producing target. The cathode (C), the grid (G), and the two anodes (A1, A2) are shown inside the chamber.

Figure 2

Anode spectra from several ${}^{242}\mathrm{Pu}$ spontaneous fission runs. Alpha particles are visible below channel 200. Exponential fits on the low-energy side of the spectrum are displayed with solid lines.

Figure 3

Overview of the experimental data and evaluated nuclear data for the neutron-induced fission cross section of ${}^{242}\mathrm{Pu}$. JEFF-3.2 evaluation follows the data of Weigmann et al.