Investigation of the Neutron Response Function of a Liquid Scintillation Detector

The determination of a liquid scintillation detector’s neutron response matrix is desirable because it can be used for determining the incident neutral particle flux, which may allow for source identification. The relationship between the amount of light pulsed from the detector and the energy deposited in the detection volume must be known such that an accurate response matrix can be calculated. Previous measurements have shown that this relationship can be expressed empirically using a quadratic polynomial. Thus, the goal of this work is to determine this empirical relationship for the EJ-309 organic liquid scintillation detector. A time-of-flight measurement of 252Cf was taken using this detector, and the energy of each pulse was empirically determined. MCNP-PoliMi was used to accurately model this detector, and a specialized FORTRAN post-processing algorithm was used to simulate a pulse height distribution for this detector. Using the empirical relationship determined form the time-of-flight measurement, a pulse height distribution was generated using MCNP-PoliMi that compared favorably to its measured equivalent for neutron energies less than 4 MeV.