CTOF Measurements and Monte Carlo Analyses of Neutron Spectra for the   Backward Direction from a Copper Target Irradiated with 800, 1000, and 1200   MeV Protons
  A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of the neutron spectrum at an angle of 175 deg from the initial proton beam direction, which hits a face plane of a cylindrical copper target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, GEANT4, and the MCNP6 codes and that measured for 800, 1000, and 1200 MeV protons. The transport codes tested here describe with different success the measured spectra, depending on the energy of the detected neutrons and on the incident proton energy, but all the models agree reasonably well with our data. 
I. L. Azhgirey, V. I. Belyakov-Bodin, I. I. Degtyarev, N. P. Smirnov,   S. G. Mashnik
nucl-ex nucl-th