Alumni

Current research / employment

Photon counting X-ray detectors are gaining increasing interest in medical imaging and other applications. In contrast to conventional systems which integrate the charge released in the sensor they are able to count single photons. The Medipix2 detector is such a detector. With this detector it is possible to determine the energy of the incoming X-ray photon which provides valuable information.

Exploiting this we are able to determine the quality and quantity of materials. One application is the quantitative detection of contrast agents in medical imaging. Among other advantages this helps to reduce the dose for the patient compared to conventional methods.

Silicon, the common sensor material, however is due to its low absorption efficiency not adequate for most medical applications. Therefore there is a huge demand for high-Z sensor materials such as Cadmium Telluride (CdTe). This II-VI compound semiconductor which can be operated at room temperature due to its large band gap (1.5 eV) has a high atomic number (ZCd=48 and ZTe=52). This makes him a promising candidate for the sensor material. As there has been made great progress in the last years concerning quality in terms of homogeniety and charge transport properties on the one hand and comercial availability on the other hand I was able to carry out detailed studies on the spectral performance of such a detector.For this reason new high-Z sensor materials like CdTe have to be investigated.

In the first part of my Phd work I investigated the influence of pixel pitch and pixel pad size on the spectroscopic behaviour of the detector in order to find a proper combination for material reconstruction with a CdTe sensor.

The second part of my Phd work deals with the development of the material reconstruction strategy for a CdTe sensor. I implemented the knowledge gained from the measurements with this CdTe detectors in our MC-simulation tool ROSI. With this simulation tool I am able to simulate the energy response functions which are crucial for material reconstruction.


Publications E. Guni, J. Durst, T. Michel, G. Anton, Material reconstruction with the Medipix2 detector with CdTe sensor, submitted to JINST, , , (2010)

E. Guni, J. Durst, T. Michel, G. Anton, M. Fiederle, A. Fauler, A. Zwerger, The influence of pixel pitch and electrode size on the spectroscopic performance of a photon counting pixel detector with CdTe sensor, submitted to Trans. Nucl. Sci., , , (2010)

T. Koenig, A. Zwerger, M. Zuber, P. Schuenke, S. Nill, E. Guni, A. Fauler, M. Fiederle, U. Oelfke, Commissioning of a 1 mm Thick CdTe Medipix Hexa Detector with 165 µm pixel pitch, submitted to NIM A, , , (2010)

T. Koenig, A. Zwerger, M. Zuber, P. Schuenke, S. Nill, E. Guni, A. Fauler, M. Fiederle, U. Oelfke, Spectral resoluton of a CdTe Medipix2 MXR Hexa Detector with a 165 μm pixel pitch, submitted to JINST, , , (2010)