Application of Controlled-Drift Detectors to Spectroscopic X-Ray Imaging

The controlled-drift detector (CDD) is a fully- depleted silicon detector that allows 2-D position sensing and energy spectroscopy of X-rays in the range 1-30 keV with excellent time resolution (few tens of mus) and limited readout channels. Its working principle is based on the generation of equally spaced potential wells along the drift direction by applying an externally controlled perturbation to the linear drift potential. Operating the detector in integrate-readout mode the X-ray incident position in the drift direction is given by the measurement of the electron drift time while the X-ray energy is obtained from the measurement of the electron charge. A further relevant benefit of the short integration time is the possibility to operate the CDD at room temperature still having an acceptable energy resolution. For more demanding spectroscopic applications the ultimate energy resolution can be reached by moderately cooling the detector. In this paper we will focus on the applications of CDDs to two advanced X-ray spectroscopic imaging techniques, namely X-ray fluorescence imaging and X- ray diffraction-enhanced imaging.