Excitation functions of Cr-50(n,np+pn+d)V-49, Ni-58(n,alpha)Fe-55, Ni-58(n,alpha p+p alpha)Mn-54 and Ni-62(n,alpha)Fe-59 reactions

Excitation functions were measured for the Cr-50(n, np + pn + d)V-49, Ni-58 (n, alpha)Fe-55, Ni-58(n, alpha p + p alpha)Mn-54 and Ni-62(n, alpha)Fe-59 reactions from 7.5 to 19.4 MeV. Use was made of the activation technique in combination with non-destructive high-resolution gamma-ray spectrometry or X-ray spectrometry after radiochemical separation and thin sample preparat ion. Quasimonoenergetic neutrons produced via the H-2(d, n)He-3 and H-3(d, n)He-4 reactions were used to irradiate samples of metallic natural chromiu m and nickel. The neutron flux densities were determined via the Al-27(n, a lpha)Na-24 (for E-n < 12.5 MeV) and Nb-93(n, 2n)Nb-92m (for E-n > 12.5 MeV) monitor reactions. Apart from the Ni-58(n, alpha p + p alpha)Mn-54 reactio n, our results represent the first cross sections beyond 15 MeV. The values for the Ni-58(n, alpha)Fe-55 reaction between 7.5 and 12.3 MeV are lower t han those in an earlier activation experiment but support the lower trend o f literature values determined via the charged particle detection method. A renormalisation of the earlier activation data with respect to the more re cent monitor cross section values reduces the discrepancy. Statistical mode l calculations incorporating precompound effects were found to be in good a greement with the present data, depicting that both first and second chance emission of nucleons are treated satisfactorily in the calculations.