Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing ¹⁹F

In the present study ⌀ 5''× 3'' and ⌀ 2''× 2'' EJ-313 liquid fluorocarbon as well as ⌀ 2'' × 3'' BaF₂ scintillators were exposed to neutrons from a ²⁵²Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β⁻ particles with maximum endpoint energy of 10.4 MeV from the n+¹⁹F reactions were studied. Response of a ⌀ 5'' × 3'' BC-408 plastic scintillator was also studied as a reference. The β⁻ particles are the products of interaction of fast neutrons with ¹⁹F which is a component of the EJ-313 and BaF₂ scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a ²⁵²Cf source showed that the relative neutron detection efficiency ratio, defined as ε_BaF2 / ε_{EJ−313−5''}, is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF₂, respectively. Moreover, the ⌀ 5'' EJ-313 and side-on oriented BaF₂ were also exposed to neutrons from the D+T neutron generator, and the relative efficiency ε_BaF2 / ε_{EJ−313−5''} was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF₂ detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility