X-Y position readout of a YAP : Ce crystal matrix using wavelength-shifting fibers

A set of preliminary test results of a detector prototype for positron emis sion tomography applications is presented. The detector is made of a YAP:Ce finger crystal (2 x 2 x 30 mm(3) each) matrix coupled to a set of square s ection wavelength-shifting fibers (one fiber for each matrix row and one fi ber for each matrix column) read by a position-sensitive detector. The reco gnition of each fiber allows the determination of the x-y position of the s cintillation event. The light yield of the system has been investigated: al l possible light loss factors have been taken into account to evaluate the expected signal. Experimental measurements with a single-pixel hybrid photo diodes have been performed. We have measured about ten photoelectrons for a deposit of 511 keV in the scintillator for each coordinate. Preliminary po sition measurements with a small 5 x 5 matrix are presented.