Measurement of Sub-Coulomb-Barrier Charged Particles Emitted from Aluminum and Titanium Bombarded by 15-MeV Neutrons

Cross Sections for (n,xp), (n,xd), and (n,xα) reactions induced by 15-MeV neutrons on ²⁷Al, ⁴⁶Ti, and ⁴⁸Ti have been measured with a quadrupole spectrometer. Particles with energies as low as 800 keV were detected. Large sub-Coulomb-barrier peaks are found in the proton spectra from ²⁷Al and ⁴⁶Ti, but not from ⁴⁸Ti; alpha-particle and deuteron spectra do not show such a peak. The presence or absence of such a peak is found to be related to the importance of the (n,n’p) reaction for a given isotope. Enhancement of the total proton-pro-duction cross section by almost a factor of 2 through such reactions is found for ²⁷Al and ⁴⁶Ti