The role of target geometry in 14 MeV neutron capture cross-section measurements

Multiple Reaction Correction to 15 MeV Neutron Capture Cross Section in115In

“…For accurate measurements the present target-head should be replaced by a thin-window aluminium head, i.e. such as used by Valkonen and Kantele [15]. Furthermore, the contribution of low-energy secondary neutrons should be minimized by using small, thin samples and small target-sample distances.…”

“…Measurements of the y-ray spectra [1-51 following the capture of [14][15] MeV neutrons indicate a smooth dependence of the capture cross sections on the mass number. These cross sections, derived by integrating the partial cross sections for y-rays to bound states in the formed nuclei, increase with mass number up to A -60 to be nearly constant, about 1 mb, for nuclei with A > 60.…”

“…Drake et al [4] noted that a contamination of about only 19; of secondary neutrons [from processes like (n,2n), (n,n') and (n,pn) in the sample or surrounding material] can seriously disturb the activation results for deformed nuclei. Kantele and Valkonen [15] found that the activation results for some deformed nuclei strongly depend on the target geometry. With an improved target arrangement they obtained capture cross sections of 14.5 MeV neutrons in agreement with those determined by the spectrum method.…”

“…The same representation as Valkonen and Kantele[15] have been used i.e. the "apparent activation cross section" means the value obtained from comparison with the known cross section of the 27Al(n,a)24Na reaction.…”