Scintillation detection using a silicon drift chamber with on-chip electronics

The performances of a Silicon Drift Chamber (SDC), having a diameter of 3 mm, as scintillation light photodetector have been experimentally evaluated on a prototype of hard X-ray spectrometer employing a Csl(Tl) crystal of the same diameter and 5 mm thick. The SDC, with on-chip electronics, is characterized by an electronics noise considerably lower than that exhibited by a conventional photodiode of equal area and thickness. Consequently, the present hard X-ray detector may operate on a wide energy range, with a minimum energy threshold of about 10 keV at room temperature or lower than 5 keV below 10°C. The measured energy resolution at room temperature is 7.49% FWHM at 122 keV and 4.34% FWHM at 662 keV. The same SDC photodetector has been also used together with a Csl(Tl) crystal having a thickness of 10 mm and, consequently, a useful energy range extending up to soft γ-ray energies. While at room temperature the energy resolutions of the two detector configurations are substantially identical, below 10°C the configuration using the smaller crystal shows appreciably better performances.