Development of experimental technique for measurement of (n, xn) double-differential cross sections above 20 MeV

The experimental technique for measurement of (n, xn) double differential cross sections above 20 MeV has been developed with continuous-energy neutrons up to 400 MeV. Neutrons were produced in the spallation reaction by the 800-MeV proton beam, which was incident on a thick, heavily shielded tungsten target at the WNR facility at Los Alamos National Laboratory. The energies of incident neutrons were determined by the time-of-flight method. Emitted neutrons were detected by the recoil proton method at 15°, 30° and 90°. A phoswich detector consisting of NaI(Tl) and NE102A plastic scintillators was used for detecting recoil protons. We obtained the neutron energy spectra by use of the unfolding code, FERDO. The response functions of the NaI(Tl) scintillator for protons were calculated by the calculation code of Particle and Heavy Ion Trasnport code System (PHITS). We compared the experimental cross section data with the calculations by the PHITS and QMD codes.