A system for precise determination of effective atomic number by beta backscatter

A compact instrument capable of determining the effective atomic number (Z_eff) of a target has been developed and characterized. It is a nondestructive sensor which utilizes a cadmium telluride solid-state detector and a ⁹⁰Sr/⁹⁰Y source in a backscatter geometry. The spectrum of the backscattered beta particles depends on the target atomic number. Measurements show that, by using the mean energy of the backscatter spectrum, the average effective Atomic number can be determined to better than ±1Z . The system includes data acquisition and analysis software which runs on a personal computer. The system was designed to be flexible enough to be used for a variety of applications by changing the data analysis algorithms and the source type and energy