Multichannel spectrum analysis for a gamma-ray imaging camera

The US Department of Energy's robotics for nuclear reactors programs include the development of a gamma-ray imaging camera to locate and identify radiation fields typical of commercial reactor environments. The raster scanning camera is a lead-shielded bismuth germanate scintillator coupled to a photomultiplier tube operated in pulse mode. The camera is mounted on a rotating, tilting platform to allow two-dimensional scanning and requires a movable shutter to subtract background radiation. While previous work produced monochromatic images, this paper discusses colored images now available through a multichannel spectrum analysis at each pixel location, and typical images are shown. Scanning operation is controlled by a personal computer-based system with an independent multichannel analyzer (MCA) board that allows for near-real-time spectrum analysis of a pixel position while the following position is being measured. The controlling routine operates the camera tilt, rotation, and shutter movement; acquires data from the MCA; and calls the peak search analysis routine