Use of retro-reflective tape for improving spatial resolution of scintillation detectors

The authors 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. The authors expect this retro-reflective property to improve spatial resolution in large continuous crystals relative to that seen with Teflon when the reflective tape is coupled to the front (radiation incident) side of the crystal. Three CsI(Tl) crystals were evaluated of dimensions 5.8 cm x 5.6 cm x 5 mm, 6 cm x 6 cm x 12 mm, and 6 cm x 6 cm x 20 mm by stepping a collimated /sup 99m/Tc source across the crystal face. Images were taken with the crystal coupled to a PSPMT. Energy resolution and light collection were similar in both the reflector and Teflon situations. Average spatial resolution in the linear (central) region of the 5 mm thick crystal with black tape wrapped around the sides was measured to be 3.6 /spl plusmn/ 0.3 mm and 5.0 /spl plusmn/ 0.3 mm for the Retro Reflective tape and the Teflon tape, respectively.