The Weighting Function of a Neutron Capture Detection System

A set of efficiencies and response functions for 18 gamma rays in the range from 0.2 to 8.4 MeV has been experimentally determined via a (p, gamma) coincidence method for a neutron capture detection setup. This consists of two cylindrical deuterated hexabenzene (C6D6) liquid scintillators placed symmetrically and normally with respect to the beam and operated in sum mode. A pulse-height weighting function is derived from this data set and applied to the measurement of neutron capture in the 1.15-keV resonance of Fe-56 relative to capture in the 5.2-eV resonance of Ag-109. A value of GAMMA-n = 62.9 +/- 2.1 meV has been obtained for the neutron width, in good agreement with the value of GAMMA-n = 61.7 +/- 0.9 meV from transmission measurements. The extension of the validity of this weighting function to samples of different thickness and composition is discussed.