Measurement and model analysis of cross sections for Cr, Fe, Co, and Ni from threshold energy to 150 MeV

Kunieda, Satoshi  ; Haight, R. C.*; Kawano, Toshihiko*; Chadwick, M. B.*; Sterbenz, S. M.*; Bateman, F. B.*; Wasson, O. A.*; Grimes, S. M.*; Maier-Komor. P.*; Vonach, H.*; Fukahori, Tokio  ; Watanabe, Yukinobu*

Neutron reactions that produce alpha-particles have been investigated for energies from threshold to 150 MeV on elemental chromium, iron, Co and Ni. The cross sections were measured at the Los Alamos Neutron Science Center by direct observation of alpha-particles. The model calculations are made for statistical and pre-equilibrium processes. This study particularly focuses on the pre-equilibrium cluster emission, which is described by the clustering exciton model of Iwamoto and Harada. We calculate the alpha-particle formation factors numerically without any approximations that appeared in the original model. The calculated alpha-particle production cross sections agree well with the measured data, except for the Cr case. With a simple sensitivity study for the level density parameters, it is reported that relatively small changes in the level density parameters improve reproduction of experimental data significantly.