An imaging nuclear survey system

A combined video and gamma ray imaging system was developed to rapidly determine the location, distribution, and intensity of gamma ray sources. This instrument includes both a conventional video camera and a gamma ray imaging system based on a position sensitive PM tube, scintillator, and pinhole collimator. The gamma camera records position and energy of each interaction, determining the energy spectrum and count rate from each direction. We have used a prototype of this instrument in preliminary field test to image radioactive sources with γ ray energies between 120 keV and 2.4 MeV. This system achieves an angular resolution for the nuclear image of 6 degree with an efficiency of 3x10-6 at 1 meter, which is suitable for many nuclear applications. Sensitivity is sufficiently high that, in a low background environment, a 1 mCi 137Cs source at 5 meters can be located in <30 seconds. Alternatively, higher spatial resolution can be attained at lower efficiency and longer imaging times