Mechanically Collimated High Energy Gamma Ray Imagers

This dissertation focuses on the development of multi-hole mechanical collimators for high energy gamma ray imaging. Two variations of this collimator, the fixed multi-hole mechanical collimator and the rotating multi -hole mechanical collimator were designed, analyzed, modeled and fabricated. These collimators were used in the fabrication of three high energy mechanically collimated gamma ray imagers for nuclear industrial applications. The first gamma ray imager, the RMD-Pinhole camera, was fabricated using a pin-hole collimator, a segmented BGO detector and a position sensitive photomultiplier tube (PSPMT). The second gamma ray imager, fixed multiple hole collimated camera (FMCC), was fabricated using a multiple hole collimator, a single slab NaI(Tl) detector and a PSPMT. The third gamma ray imager, rotating multiple hole collimated camera (RMCC), was fabricated using a double layered multiple hole collimator and an array of CsI(Tl) detectors each coupled to a PIN photodiode. The response of the cameras to gamma rays from 122 keV to 810 keV was measured. Performance parameters of these cameras have been been measured and measured, including their energy resolution, angular resolution, image uniformity and sensitivity among others are measured and presented. The measured energy resolutions ranged from 7% FWHM at 662 keV (RMCC) to 25% FWHM at 662 keV (RMD -Pinhole). The angular resolutions measured varied from 4^circ FWHM (RMCC) at 810 keV to 6^circ FWHM at 412 keV (FMCC). The ability of the cameras to image distributed sources is demonstrated using several source distributions shown here.