Measurement of Neutron Inelastic Scattering on 56Fe, 48Ti, and 52Cr at the CSNS Back-n

Precise measurements of γ-ray angular distributions and cross sections from neutron inelastic scattering are crucial for both fundamental nuclear physics and applied nuclear technology. However, such measurements at white neutron sources are severely hampered by intense pulse pile-up, particularly in the fast neutron region. This work presents a comprehensive investigation of (n, n′ γ) reactions on 56Fe, 48Ti, and 52Cr at the CSNS Back-n beamline. A key innovation was the deployment of a high-performance LaBr3(Ce) detector array coupled with an advanced pulse pile-up recovery algorithm, which successfully reconstructs individual events at extreme counting rates up to 10^7 s−1 and resolves pulses separated by as little as 10 ns. This capability eliminated the need for traditional, model-dependent efficiency corrections and enabled the extraction of clean γ-ray spectra across the entire neutron energy range. We report the incident-energy-dependent Legendre coefficients (a2, a4) for five characteristic E2 transitions from 0.9 to 14 MeV. Furthermore, the absolute inelastic scattering cross sections for the 847-keV state in 56Fe and the 1434-keV state in 52Cr were determined using a relative measurement method. Our results show excellent agreement with previous experimental data and provide an experimental benchmark for validating and constraining theoretical nuclear reaction models.