Neutron induced fission cross section measurements of ${}^{240}$Pu and ${}^{242}$Pu relative to the neutron-proton scattering cross section at 2.5 and 14.8 MeV

A measurement campaign to determine neutron induced fission cross sections of ${}^{240}$Pu and ${}^{242}$Pu at 2.51 and 14.83 MeV has been carried out at the 3.7 MV Van De Graaff linear accelerator at Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Two identical Frisch Grid fission chambers, housing back to back a ${}^{238}$U and a ${}^A$Pu fertile sample (A = 240 or A = 242), were employed to detect the total fission yield. The neutron fluence was measured with the recoil proton telescope (T1) (Dangendorf et al. Nucl Instrum Methods Phys Res A 469:205-215, 2001), which is the German primary standard for neutron fluence measurements. The two measurements were related using a de Pangher long counter (Nolte and Thomas Metrologia 48:274-291, 2011) and the integrated beam current as monitors. The experimental results have an average uncertainty of 3-4% both at 2.51 MeV and at 14.83 MeV and have been compared to the data available in literature. The employed set-up allowed measurements of ${}^{238}$U σ${}_{(n,f)}$ in parallel. The results confirm the most recent standard libraries at 2.51 and 14.83 MeV.