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,γ) 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 ⁵⁶Fe relative to capture in the 5.2-eV resonance of ¹⁰⁹Ag. A value of Γ_n = 62.9 ± 2.1 meV has been obtained for the neutron width, in good agreement with the value of Γ_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.