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We measured the charge collection efficiency and energy resolution at 60 keV and 122 keV for single-element Cd/sub 0.8/Zn/sub 0.2/Te semiconductor detectors 2/spl times/10/spl times/10 mm/sup 3/, irradiated transverse to the electric field, in view of their possible use for digital radiography. Charge collection efficiency, energy resolution and charge collection time have been measured as a function of the bias voltage. The detector's imaging performance was evaluated, using a scanning procedure, by measurements (at 60 keV) of the line spread function and edge response function of the imaging system; metallic test objects and bone tissue were imaged. Image contrast values as low as C=10% were obtained for a minimum 5:1 S.N.R.

The use of a double sided mu -strip silicon crystal for X-ray detection is being investigated. The detector is 300 mu m thick and the read-out pitch is 100 mu m for both sides. It operates in capacitance charge division mode by means of floating strips between read-out strips. The detector has been irradiated by /sup 241/Am and /sup 109/Cd sources. Different zones within the 100- mu m read-out pitch have been individually exposed. The following characteristics have been studied as a function of the impact point of the photon: (a) the charge collection mechanism; (b) the relative detection efficiency; (c) the energy resolution; and (d) the spatial resolution. The absolute efficiency of the detector has been measured at three energy values. >

We present some additional results obtained with the BETAview system, a digital system for real time /spl beta/-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. We describe the system assembled with a Si detector, 300-/spl mu/m thick, segmented into 64 /spl times/64 square pixels with 170-/spl mu/m pitch. The solid-state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1 Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e/sup -/ (corresponding about 5 keV in Si), and contains a 15-bit counter. The detector sensitive area is about 1 cm/sup 2/, but several detectors could be assembled in arrays. The measured background counts were about 3.5/spl times/10/sup -2/ cps/cm/sup 2/, which implies a very high sensitivity of the device. The detection threshold used in this experiment was /spl sim/15 keV. We show the results obtained in the real-time monitoring of two biological dynamic processes: an amino acid uptake by living cells and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([/sup 14/C]L-Leucine) into Octopus vulgaris eggs cells. The results, described in Section III-B, show that after about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. In Sections III-C and III-D, we also describe the successful performance of the /spl beta/-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different /sup 32/P-radiolabeled nucleotides.

A portable system has been developed for the control and the readout of a 64/spl times/64 pixel silicon hybrid detector (1.1/spl times/1.1 cm/sup 2/ active area), bump-bonded to the Medipix1 readout chip. This system was originally designed for biomedial imaging applications and is based on standard commercial digital I/O boards and a compact dedicated interface (p-MUROS), connected to the portable PC. The Medipix1 chip is hosted in a 257 Pin Grid Array chip carrier directly placed on the p-MUROS board. This board is the simplified version of the MUROS1 readout board already developed in the framework of the Medipix collaboration. User-friendly software system (Medisoft 3.3) has been written to provide control of the system and image acquisition, display and processing. This complete hardware/software imaging system has been used with laboratory /spl alpha/, /spl beta/ and /spl gamma/ sources for test purposes and represents the portable version of a desktop imaging system developed for /spl beta/-autoradiography. The system description and complete imaging tests are presented. Additional applications include the monitoring of the flux and the energy spectrum of X-rays tubes.