Gamma-ray spectra from the radiative capture of 14.1 MeV neutrons in Mg, Si, P and Ca

Multiple-Reaction Correction to the Capture Cross Section

“…Several suggestions for the discrepancies have been put forward, 1 " 3 but the proposal of Halpern as quoted in Ref 0 3, namely that previous measurements may have included (n, n f ), (n,pn f ), (n, 2n'), etc, followed by (w', y), appears to be correcto Indeed Kantele and Valkonen 4 have carefully extrapolated their 14 0 5-MeV activation measurements to zero-thickness targets in order to exclude multiple-reaction effects and thereby get cross sections of the same magnitude as the spectrum measurements of Drake, Bergqvist, and McDaniels 3 and Cvelbar, Hudoklin, and Potokar. 2 It is the purpose of this Letter to emphasize that this Halpern-Drake multiple-reaction correction is also of importance below 14 MeV, and to give a few examples. The correction begins for energies above the first level of the target and consists of the subtraction from the direct primary reaction of reactions caused by secondary neutrons resulting from (n, n'), (n,2n') y (n,pn f ), etc.…”