A Proton Recoil Telescope for the characterisation of the neutron beam at n_TOF

Abstract

The neutron induced fission cross section of 235U is extensively used as a reference for neutron fluence measurements in various applications. At intermediate energies, the 235U(n,f) cross section plays an important role also for fundamental nuclear physics. Despite its widespread use, no data exist on neutroninduced fission of 235U above 200 MeV. Hence, there is a clear and long-standing demand from the International Atomic Energy Agency (IAEA) to complement the experimental database from 20 MeV to 1 GeV. For this purpose at the neutron facility n TOF at CERN the measurement of 235U(n,f) cross section was planned in October 2018, taking advantage of the intense neutron beam with a wide energy spectrum available in the experimental area. The cross section measurement will be performed relative to the elastic neutron-proton scattering, a very well known reaction generally accepted as primary reference. A prototype of the Proton Recoil Telescope detector, that will be used to measure the incident neutron flux, has been built and tested at n TOF in 2017.