Performance of position sensitive scintillator detectors when readout with a low noise photodevice
The technique of position sensitive scintillating bar detectors used as the building blocks of position sensitive planes offers the remarkable advantage of greatly reducing the number of readout electronic chains. A position sensitive bar is usually readout by two photo-detectors and, combining the two signals, energy and position of an interacting particle or gamma-ray can be evaluated. In this kind of detector the performances can suffer from the double readout that introduces the noise and uncertainty of two readout systems. The use of Silicon Drift Chamber as a photo-detector opens new perspectives in the design of scintillating bar detectors. In this case the high quantum efficiency of Si for light detection and the very low noise of the device practically cancel the disadvantages of a double readout system. In this work the results achieved stimulating with gamma rays of different energies scintillating bars with square cross section of 3 mm and various length from 15 cm to few cm, with double side Silicon Drift Chamber readout are presented and discussed. For these test an old scintillating material as CsI(Tl) has been chosen manly for its easy availability in different shapes and the good matching of the wavelength of its scintillation light with Si. The use of different materials is also discussed.
Detectors for high-resolution gamma-ray imaging based on a single CsI(Tl) scintillator coupled to an array of silicon drift detectors
Silicon drift detectors (SDDs) coupled to scintillators have been recently employed successfully in gamma-ray detection. The low value of output capacitance of an SDD allows to reach a lower electronics noise with respect to a conventional silicon photodiode. Detectors based on array of SDDs are of particular interest for gamma-ray imaging. A first prototype conceived for high-resolution imaging is based on a monolithic array of small SDDs (5 mm/sup 2/ each unit) with on-chip junction field-effect transistor (JFET). The first results obtained with a seven-elements array are here reported. For the realization of gamma detectors of larger active areas based on assembled units; SDDs of 30 mm/sup 2/ of area with external JFET have been produced. We present the experimental results obtained in the characterization of a single CsI(Tl)-SDD unit.
Gamma ray spectroscopy with CsI(Tl) scintillator coupled to silicon drift chamber
A /spl gamma/-ray detector, designed around a silicon drift chamber having a diameter of 3 mm and coupled to a CsI(Tl) scintillator of the same diameter and 10 mm thick, has been realized and extensively tested. This detector may operate over a wide energy band with a minimum energy threshold that may be set around 10 keV at room temperature or at around 4 keV at 0/spl deg/C. At the typical energy of 662 keV used to characterize a /spl gamma/-ray spectrometer, an energy resolution of 4.4% full-width at half-maximum has been measured at room temperature. This detector shows high energy resolution over the full energy range explored, 6 keV-1.27 MeV, and to our knowledge the results reported are the best ever obtained with a scintillator.