In applications where high spatial resolutions in the determination of the
position of an interaction are necessary crystal matrices are often used. T
he readout of such matrices can be difficult especially if these have a lar
ge number of pixels (> 400). One possible way to solve the difficulty is by
reading out the row and the column by coupling wavelength shifting fibers
to the front and back of the matrix. Measurements have bran carried out on
the photoelectron yield of one fibre coupled to a 5 x 5 YAP:CU matrix so as
to prove the principle. The fibre was read out using a single pixel HPD. T
he results of these measurements will be presented. (C) 2001 Elsevier Scien
ce B.V. All rights reserved.