Measurement of neutron-induced fission cross sections of 235U and 238U relative to n-p scattering at CSNS Back-n facility

U-235 and U-238 are very important isotopes in the nuclear energy system. Their neutron-induced fission cross sections have been measured intensively and evaluated as standard up to 200 MeV. However, as a matter of fact, the experimental data in the high-energy region are scarce. This work reports the measurement of (235), U-238(n, f) cross sections relative to n-p scattering performed at the China Spallation Neutron Source (CSNS) back-streaming neutron facility (Back-n). Preliminary results of (235), U-238(n, f) cross sections from 10 to 66 MeV are obtained, which are generally following the shape of the IAEA standard. However, significant discrepancies are observed at some given energies, which will be further studied.