Large-volume Si(Li) orthogonal-strip detectors for Compton-effect-based instruments

Recent developments of large-area Si(Li) orthogonal-strip detectors have revealed their capability for applications in Compton-effect-based instruments. Some inherent advantages of silicon such as the dominance of Compton scattering in photon interactions and operation at room or somewhat lower temperature combined with the availability of large-volume Si(Li) detectors could stimulate the development of powerful Compton instruments. Several diodes 10 mm in thickness with a diameter of 102 mm were fabricated. Two 10 mm thick diodes were cut to form a 74 mm/spl times/74 mm square with slightly rounded corners. The same position-sensitive structure, 32 strips with a pitch of 2 mm, was produced on the thin Li-diffused n-contact and boron-implanted p/sup +/-contact by means of photolithography and plasma etched grooves. The position-sensitive area of 64 mm/spl times/64 mm is surrounded by a 5 mm wide guard-ring. One of these 10 mm thick Si(Li) orthogonal-strip detectors has been mounted in a cryostat prepared at Lawrence Livermore National Laboratory (LLNL). The detector will be extensively tested there with the goal of being integrated into the Compact Si+Ge Compton camera system consisting of this Si(Li) and a HPGe orthogonal-strip detector.