The OECD has recently organized benchmarks [105, 106] comparing available INC calculations. These benchmarks have shown that small — angle neutron spectra were particularly sensitive tests of the code.

Small-angle neutron spectra

The SATURNE group studied these observables before the close-down of the Saclay (France) synchrotron SATURNE. Figure 6.1 shows the small — angle neutron spectra for a number of targets and 1 GeV incident protons. The data are compared with a calculation using the Bertini INC and with one using the Cugnon INC. Although still not perfect, it is clear that the Cugnon INC is a significant improvement over the Bertini INC. The figure shows the importance of the delta charge exchange peak, 300 MeV lower than the high-energy quasi-elastic peak. Both peaks correspond to a process by which the proton is changed into a neutron. Figure 6.2 shows similar results and comparisons made by the Los Alamos group [90]. Here again, the improvement obtained with the more modern ISABEL [86] INC calculation is clear. The delta peak involves real charged pion exchange, the quasi-elastic peak the excitation of the target into an isobar analogue state. The delta peak is a preferential doorway for the energy deposition of

the high-energy proton (or neutron) into the target nucleus. Indeed, for heavy nuclei the average energy deposition is close to 300 MeV.