An ISPA-camera for gamma rays

With the recently developed ISPA (imaging silicon pixel array)-tube attached either to a planar YAlO/sub 3/(Ce) (YAP) disc (1 mm thick) or to a matrix of optically-separated YAP-crystals (5 mm high, 0.6/spl times/n.6 mm/sup 2/ cross-section) we achieved high spatial resolution of /sup 57/Co-122 keV photons. The vacuum-sealed ISPA-tube is only 4 cm long with 3.5 cm diameter and consists of a photocathode viewed at 3cm distance by a silicon pixel chip, directly detecting the photoelectrons. The chip-anode consists of 1024 rectangular pixels with 73 /spl mu/m/spl times/500 /spl mu/m edges, each bump-bonded to their individual front-end electronics. The total pixel array read-out time is 10 ps. The measured intrinsic spatial resolutions (FWHM) of this ISPA-camera are 700 /spl mu/m (planar YAP) and 310 /spl mu/m (YAP-matrix). Apart from its already demonstrated application for particle tracking with scintillating fibers, the ISPA-tube provides also an excellent tool in medicine, biology, and chemistry.