High-resolution X-ray imaging using the signal time dependence on a double-sided silicon detector

The possibility of using drift times for electrons and holes in an edge-on double-sided silicon strip detector to achieve a high resolution X-ray image has been investigated with help of computer simulations. The detector is in a scanned slit X-ray imaging geometry and collects electrons and holes on opposite sides of the silicon wafer. The time displacement between collection of electrons and holes is related to the position across the detector where the X-ray photon converted and the results of the investigation indicate this can be translated into a spatial resolution better than 20 mu m. The advantage of this method is that the resolution is not limited by the slit size allowing several times as many photons contribute to the image and thus reduce the scan-time. The study assumed a 300 mu m thick detector which for a slit-width with the same size results in a 10 times more efficient use of the X-ray source compared to a 30 mu m slit. A thicker detector increases this number, but leads to a higher rate of coincidences that would interfere with the time measurements. It was calculated that an average of 2 MHz incoming photons per strip would give less than 5% coincidences. (C) 1999 Elsevier Science B.V. All rights reserved.