Year
2007
Abstract
To address the need for high resolution detection systems to be used in portal monitors and mobile search systems, an integrated gamma ray spectrometer, incorporating a germanium detector with integral mechanical cooling, digital signal processing electronics, MCA, and communications has been developed. This modular subsystem can be used in a wide variety of applications, including use in stationary or mobile systems for the detection of radioactive materials. To have the sensitivity needed for these applications the detectors must have good low and medium energy detection efficiency coupled with excellent spectral peak resolution. The resolution removes peak overlaps and helps to overcome the problems of masking with common nuclides. In a situation where either the spectrometer or the material is moving, the Field of View (FOV) determines the time the material contributes to the spectrum. The absolute efficiency and background determine the minimum detectable or identifiable quantity for the material in the FOV. To characterize the expected performance in a general system, the absolute efficiency was measured for several units over the energy range of 80 keV to 1.8 MeV. The horizontal FOV is limited by collimators and was measured for several distances corresponding to the ANSI N42.38 test criteria. The vertical FOV (no collimation), important to determine the detector spacing, was also measured. The background was measured in a typical pedestrian portal situation. The measurements presented show this unit can be applied to a wide variety of monitoring situations.