The use of retro-reflective tape for improving spatial resolution of scintillation detectors

We are investigating the use of a retro-reflective tape (3M Industries), which reflects light along a line parallel to the incident light, as a substitute for Teflon tape or other reflective material used with scintillation crystals. We expect this retro-reflective property to improve the spatial resolution in large continuous crystals relative to that seen with Teflon, or other reflective coatings, when the reflective tape is coupled to the front (radiation incident) side of the crystal. Three CsI(TI) crystals of dimensions 5.8 cm × 5.6 cm × 5 mm, 6 cm × 6 cm × 12 mm, and 6 cm × 6 cm × 20 mm were evaluated by stepping a collimated ^99mTc source across the crystal face. Images were taken with the crystal coupled to a position-sensitive photomultiplier tube. The energy resolution and signal amplitude were similar for both the reflector and Teflon. The average spatial resolution in the central region of the 5-mm-thick crystal with black sides was measured to be 3.6 ± 0.3 mm and 5.0 ± 0.3 mm for retro-reflective tape and Teflon tape, respectively