Neutron activation cross-section measurements from 16 to 20 MeV for isotopes of F, Na, Mg, Al, Si, P, Cl, Ti, V, Mn, Fe, Nb, Sn and Ba

Cross sections have been measured with the activation technique at various neutron energies in the range of 16.0 to 20.5 MeV for the following 22 reac tions: F-19(n, p)O-19, Na-23(n, p) Ne-23, Na-23(n,alpha)F-20, Mg-25(n, p)Na -25, Al-27(n,p)Mg-27, Si-28(n, p)Al-28, Si-29(n, p)Al-29, Si-29(n, np + pn + d)Al-28, (31)p(n, alpha)Al-28, Cl-35(n, 2n)34mCl, Cl-37(n, p)S-37, Ti-46( n, p) (SC)-S-46m, Ti-50(n, p)Sc50+m, V-51(n, p) Ti-51, Mn-55 (n, alpha)V-52 , Fe-56 (n, p) Mn-56, Fe-57(n, np + pn + d)Mn-56, Fe-57(n,p)Mn-57, Nb-93(n, alpha)Y-90m, Nb-93(n, 2n)Nb-92m, Sn-119(n,p)In-119g, and Ba-138(n,2n)Ba-137 m. The half-lives for the reaction products range from 11 s to 10.15 days. Quasi monoenergetic neutrons were produced via the H-3(d, n)He-4 reaction. In some cases isotopically enriched materials were used to enhance the reac tion yield or to facilitate correction for interfering reactions leading to the same product. The gamma rays emitted from the irradiated samples were measured with a high-purity germanium detector. A pneumatic sample transpor t system was used to limit the decay of the radioactive products between ne utron irradiation and gamma-ray counting. All cross sections were obtained as ratios to the standard reaction Al-27(n, alpha)Na-24, using as secondary neutron fluence references the Al-27(n, p)Mg-27 reaction as well as a cali brated Bonner sphere. Corrections have been applied for sample irradiation and counting environment geometric effects, neutron absorption and multiple scattering, time variation of neutron-source strength, neutron-source angu lar distributions, secondary neutrons from the target, gamma-ray absorption , and gamma-ray sum coincidences. A detailed analysis of the uncertainty so urces was performed The present results are compared with other measurement s and evaluated data. For seven reactions, measured cross sections have bee n obtained for the first time beyond 15 MeV. These new data help appreciabl y to resolve discrepancies in evaluated data files.