A CdTe pixel detector–CMOS preamplifier for room temperature high sensitivity and energy resolution X and γ ray spectroscopic imaging

X and γ ray imaging devices with spectroscopic capabilities are strongly demanded in industrial, medical and scientific applications. CdTe detectors with Schottky contacts are very interesting due to their high absorption coefficient and the low leakage current of the reverse-biased rectifying junction even at room temperature. A CdTe detector with a pixel size of 0.75 mm × 0.75 mm has been coupled to SIRIO, a research-grade charge sensitive preamplifier with 1.2 electrons r.m.s. intrinsic noise. The system has been characterized at +20 °C for X and γ ray spectroscopy with a 241Am source. An intrinsic energy resolution of 326 eV FWHM has been measured and spectral line widths from 337 eV FWHM at 2.7 keV to 843 eV FWHM at 59.54 keV have been recorded. The linearity error of the spectrometer has been measured to be within ±0.1% in the 2.7 keV–59 keV energy range. Effects of escaping photons and fluorescences have been resolved and identified. The line widening sources and their effect on Fano factor determination have been discussed.