Characterization of small CdTe detectors to be used for linear and matrix arrays

For a better understanding of the performances of X-ray and gamma-ray detectors made of CdTe crystals, the authors have investigated two different operation modes. The first one, the ´type A´ solution, has the direction of the bias electric field parallel to the direction of the impinging radiation; the second one, named the ´type B´ solution, has the bias electric field perpendicular to this direction. Experimental results and a Monte Carlo simulation applied to type A and B detectors have underlined the advantage of the former configuration for photon energies of the order to 100 keV and of the latter design for photon energies on the order of 500-700 keV, these higher values being typical for medical and industrial applications. Type B detectors of 2.5 mm*2.5 mm*20 mm show a very good energy resolution (full width at half maximum 10 keV for 511 keV and of 11 keV for 662 keV) and an acceptable time resolution (45 ns) even for a preliminary and not-optimized experimental set-up. The Monte Carlo simulation is also described in detail.<>