Plutonium Test Plan ORNL-VNIIEF Collaboration

The goal of this test is to collect the cross correlation and HOS signatures from four detectors, arranged in a tetrahedron about different plutonium objects during ORNL/VNIIEF collaborative measurements in Sarov, Russia. The four detectors will be arranged in a tetrahedron with the plutonium object in the center of the tetrahedron. The following constraints about the detector geometry should be adhered to if, possible. The base of the tetrahedron (detectors No. 1, No. 2, and No. 3) should have 3 identical detectors (preferably 4 in. x 4 in., plastic scintillators) placed in an equilateral triangle; the length of one side of the base should be 60 cm (R{sub 12}=R{sub 23}=R{sub 13}=60 cm); the ideal height of the fourth detector above the base is {radical}(2/3) of the side of the equilateral triangle (height = {radical}(2/3) (60 cm) = 49 cm) and finally, any mismatched detector should be placed at the apex of the tetrahedron (i.e. top position). The collected signatures will be processed later. In order to perform the post processing, the peak efficiencies and neutron thresholds for each detector must be obtained by performing a standard Time-of-Flight measurement. Secondly, the response matrix data must be benchmarked for each detector/object configuration. This benchmark is determined by collecting the NMIS signatures in active mode for a californium source at two different points inside the tetrahedral volume of detectors