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 emission 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 section wavelength-shifting fibers (one fiber for each matrix row and one fiber for each matrix column) read by a position-sensitive detector. The recognition of each fiber allows the determination of the x-y position of the scintillation event. The light yield of the system has been investigated: all possible light loss factors have been taken into account to evaluate the expected signal. Experimental measurements with a single-pixel hybrid photodiodes have been performed. We have measured about ten photoelectrons for a deposit of 511 keV in the scintillator for each coordinate. Preliminary position measurements with a small 5 x 5 matrix are presented.