GAMMA-DETECTORS FOR TOMOGRAPHIC FLOW IMAGING

The significance and limitations of gamma-ray flow imaging are discuss ed, with the conclusion that there is a need for compact detectors wit h fast response. Scintillation crystals are the only practical gamma-a bsorbers which provide sufficient stopping efficiency over the whole e nergy range of interest (60 keV to 1.2 MeV). Experimental data on two scintillation light read-out devices are presented. One is the new EDP MT (electron-bombarded silicon diode photomultiplier tube) which is ca pable of count rates close to 10(7) c.p.s. over a broad energy range w hen used with a GSO crystal. A proximity-focused EDPMT version can be made compact and allows tight stacking. The second device is a very co mpact and robust photodiode. This is a good alternative for low count- rate applications (<10(5) c.p.s) with gamma energies above approximate ly 600 keV. Both detectors are suitable for process tomography in gene ral, not only flow imaging.