Assessment of reflective separator films for small crystal arrays

Thin, highly reflective, opaque separators are required to assemble compact arrays of small discrete scintillation crystals used in conjunction with photodiode array readouts in high-resolution imaging applications. Mechanical stability, individual detector performance, and ease of handling for wrapping crystals are the main factors to be considered in the choice of a suitable separator. Three different types of reflective materials were tested with 4×4 arrays of LSO, BGO and GSO: Tyvek 1058D paper, Toray Lumirror E60L Polyester Film, and 3M VM2000 Radiant Light Film. The light output and intrinsic energy resolution of individual crystals were measured as a function of their position in the arrays and the results were compared to simulation of light collection efficiency obtained with DETECT97. Optical crosstalk between adjacent and diagonal pixels was evaluated. The Lumirror film consistently yielded superior results with BGO. With LSO and GSO, the 3M reflector was found to provide slightly better light output and energy resolution. Despite the sharp cutoff in spectral reflectivity at 400 nm with this reflector, the crosstalk between adjacent LSO crystals was not found to be significant.