AN ISPA-CAMERA FOR GAMMA-RAYS

With the recently developed ISPA (Imaging Silicon Pixel Array)-tube at tached either to a planar YAlO3(Ce) (YAP) disc (1 mm thick) or to a ma trix of optically-separated YAP-crystals (5 mm high, 0.6 x 0.6 mm(2) c ross-section) we achieved high spatial resolution of Co-57-122 keV pho tons, The vacuum-sealed ISPA-tube is only 4 cm long with 3.5 cm diamet er and consists of a photocathode viewed at 3 cm distance by a silicon pixel chip, directly detecting the photoelectrons. The chip-anode con sists of 1024 rectangular pixels with 75 mu m x 500 mu m edges, each b ump-bonded to their individual front-end electronics, The total pixel array read-out time is 10 mu s. The measured intrinsic spatial resolut ions (FWHM) of this ISPA-camera are 700 mu m (planar YAP) and 310 mu m (YAP-matrix), Apart from its already demonstrated application for par ticle tracking with scintillating fibers, the ISPA-tube provides also an excellent tool in medicine, biology, and chemistry.