Dresden 2011 – wissenschaftliches Programm

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ST: Fachverband Strahlen- und Medizinphysik

ST 6: Imaging with Ionizing Radiation II

ST 6.5: Vortrag

Donnerstag, 17. März 2011, 15:00–15:15, POT 112

Improved method for the reconstruction of X-Ray Spectra with pixel detectors such as Medipix2 — •Peter Sievers^1,2, Thorsten Schneider¹, Thilo Michel², and Gisela Anton² — ¹Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig — ²ECAP, Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, 91080 Erlangen

As recently shown, it is possible to use pixelated semiconductor detectors such as Medipix2 for measuring the impinging spectra. If all interaction processes in the sensor like photo effect, compton scattering and fluorescence excitation are implemented correctly in a Monte-Carlo-Simulation, the impinging spectrum can be computed by deconvolution of the measured energy deposition spectrum with monoenergetic response functions. In this work we present an improved reconstruction algorithm to extend the working conditions for low flux fields.

For the measurements a Medipix2 was used. It consists of an ASIC which has 256x256 pixel cells with 55 μm pitch. As sensor we used a silicon layer with a thickness of 300 μm bumpbonded to the ASIC. In the analogue part of each pixel a discriminator with one energy threshold is present. This means only photons with an energy deposition in the sensor that is higher than the threshold are counted. By increasing this threshold gradually the whole deposited spectra can be scanned. In opposite to former studies such a "threshold scan" is now used directly for the deconvolution without the intermediate step of the derivation. This has the advantage of much lower relative errors and therefore has the potential to measure spectra with low statistics.