Large area silicon drift detectors for new applications in nuclear medicine imaging

In this work we have investigated the performance of a large area (1 cm/sup 2/) square shaped Silicon Drift Detector (SDD) operating as a gamma-ray detector in direct conversion mode as well as a photodetector in combination with a single crystal CsI:Tl scintillator (10 mm /spl times/ 10 mm /spl times/ 7 mm). An external FET along with a low-noise charge sensitive preamplifier was used for testing the prototype detector in the temperature range -23/spl deg/C to 26/spl deg/C. In direct conversion mode the SDD exhibited an energy resolution of 195 eV FWHM (at 5.9 keV, -23/spl deg/C, 4 /spl mu/s shaping time). Pulse height spectra and signal rise times were recorded at different locations across the SDD surface with the aid of a relocatable collimator. Depending on collimator position we measured signal rise times between 100 ns and 750 ns. After coupling the CsI-scintillator directly to the SDD surface we obtained an excellent energy resolution of 7% FWHM with an uncollimated /sup 57/Co source (122 keV, -10/spl deg/C, 12 /spl mu/s shaping time). The corresponding signal rise time was approx. 20 /spl mu/s. A short analysis regarding the different SDD-signal rise times with and without scintillator will be presented.