A new position sensing X-ray detector: working principle and experimental results

The working principle and the first experimental characterization of a new fully depleted X-ray detector, called controlled-drift detector (CDD), are presented. The detector is operated in integrate-readout mode. During the integration phase the signal electrons generated by the incident X-ray are stored in suitably engineered potential wells. During the readout phase the potential wells are removed and replaced by a uniform drift field that transports the signal electrons to the readout electrode. The drift time gives the position of incidence. Full depletion of the detector wafer allows for high X-ray efficiency and for backward illumination. The first experimental measurements demonstrate the fast readout of the integrated signal electrons achievable with a static drift field. At a drift field of 300 V/cm the measured readout speed is 0.35 cm/μs. The expected charge handling capacity is 10⁵-10⁶ electrons per pixel. The new detector provides unambiguous two-dimensional (2-D) position measurement with readout times of the order of 10 μs