Increased Range Neutron Response High Explosives Detection

The coupling of a pulsed neutron source and a depth-sensitive Compton camera based on fast inorganic scintillation crystals is proposed as a means for imaging high explosives and other materials at intermediate to long ranges. The use of scintillators allows one to deploy relatively large active detection areas, which are crucial if short measurement times are going to be achieved. The temporal response of the fast scintillation component of the BaF2 crystals that we intend to use during Phase I will not only allow precise depth-imaging, but they will also enable the position-sensing of the gamma-ray interaction location. The main focus of the Phase I research is optimizing the spatial resolution of a fast scintillation crystal bounded by two photomultiplier tubes using both: a) the variation in scintillation light intensity that reaches the ends of the crystal, and b) using the time-of-arrival differences between the measured light pulses. The results from both methods will be quantified and the optimal design will be tested using a diagnostic detector based on two-components. The angular resolution will be measured and modeled and the performance of the full-scale detector will thus be established, the fabrication of which will proceed during Phase II.