Application of CdTe and CZT detectors in ultra fast electron beam X-ray tomography

Ultra fast electron beam tomography has been developed as a novel tool for visualisation of fast processes. As in medical electron beam CT this technique is based on the generation of images from radiographs produced with a rapidly scanned electron beam. Thereby an electron beam of sufficiently high power (typically UB=150kV, power up to 10 kW) is scanned across a circular metal target producing X-rays in a small focal spot. With the rotation of the spot around an object radiographs from different viewing angles are produced and subsequently reconstructed to slice images. A fast electron beam scanner at FZD operates with beam sweeping of up to 7 kHz, producing up to 7000 images per second. The X-ray detector used in this device consists of 240 room temperature semiconductor elements operated in current mode. Photon flux at the detector is rather high, being >10^11 ph/s. The detector is sampled with 1 MHz frequency. It is known, that high flux current mode operation poses problems for semiconductor detectors made of CZT and CdTe due to polarization effects and decay time in the few hundred ns range. We have compared both types of detectors regarding their suitability in such an application. The presentation will give an overview on these results and furthermore give an introduction of this new fast imaging technique.