Hand-held radio-isotope detection and identification instrument

An instrument combining an array of Cadmium-Zinc-Telluride (CZT) detectors, a NaI scintillator, and two {sup 3}He neutron detectors has been constructed. The instrument uses the CZT array to identify radioactive materials. As an example of this application, the 3 {sigma} Minimum Detectable Activity for the 375 keV peak of {sup 238}Pu is less than 1 gram at a distance of 20 cm for a 100-second counting time. The 2 x 2 NaI scintillator has a dual purpose. First, it is used to supplement the CZT array for identification of high-energy gammas, such as those from {sup 60}Co. Second, the principle use of the NaI scintillator is to help search for radioactive material and to find a suitable measurement location on a suspect package for the CZT-based isotope-identification measurement. This detector also produces energy-corrected exposure-rate data. The {sup 3}He neutron detectors provide an additional confirmation of the presence of some plutonium isotopes. The neutron sensitivity is 90 counts per second at 20 cm from a moderated {sup 252}Cf neutron source