ISPA-tubes with scintillating YAP:Ce windows: X and gamma ray imaging

The ISPA (Imaging Silicon Pixel Array)-tube is a position sensitive photon detector based on hybrid technology. It detects light via a photocathode and an appropriate electric field accelerates the emitted photoelectrons towards a silicon pixel anode. This anode, finely segmented into pixel detectors provides binary images and allows for the self-triggering of the tube. Coupled to scintillating crystals, ISPA-tubes have been successfully tested in the field of gamma ray imaging for biomedical applications, demonstrating real capabilities in both space and energy resolution. Recently, we have demonstrated the possibility to use YAP:Ce scintillating crystals as active windows for hybrid photon detector tubes, the photocathode being directly evaporated at their inner surface. We present results obtained with a new ISPA-prototype equipped with such a window and discuss the benefit of having an input window acting as the gamma-detecting medium, in both energy and space resolution points of view