Excitation Functions of the 50Cr(n, np+pn+d)49V, 58Ni(n,alpha)55Fe, 58Ni(n, alpha.p+p.alpha)54Mn and 62Ni(n,alpha)59Fe Reactions.

Excitation functions were measured for the 50Cr(n,np+pn+d)49V, 58Ni(n,a)55Fe, 58Ni(n,ap+pa)54Mn and 62Ni(n,a)59Fe reactions from 7.5 to 19.4 MeV. Use was made of the activation technique in combination with non-destructive high-resolution g-ray spectrometry or X-ray spectrometry after radiochemical separation and thin sample preparation. Quasi-monoenergetic neutrons produced via the 2H(d,n)3He and 3H(d,n) 4He reactions were used to irradiate samples of metallic natural chromium and nickel, respectively. The neutron fluxdensities were determined via the 27Al(n,a)24Na (for En < 12.5 MeV) and 93Nb(n,2n)92mNb (for En < 12.5MeV) monitor reactions. Apart from the 58Ni(n,ap+pa)54Mn reaction, our results represent the first cross sections beyond 15 MeV. The values for the 58Ni(n,a) 55Fe reaction between 7.5 and 12.3 MeV are lower than those in an earlier activation experiment but support the lower trend of literature values determined via the charged particle detection method. A renormalisation of the earlier activation data with respect to the more recent monitor cross section values reduces the discrepancy. Statistical model calculations incorporating precompound effects were to be in good agreement with the present data, depicting that both first and second chance emission of nucleons are treated satisfactorily in the calculations.

FESSLER Andreas;  QAIM S.M.; 

1998-10-28

JRC16894