The semiconductor pixel detector TimePix (256 x256 pixels with pitch of 55 um) is a newly developed successor of the Medipix2 device. Each Timepix pixel can be operated in one of three principal modes: 1. counting of the detected particles; 2. measurement of the particle energy; 3. measurement of the time of interaction. The energy measurement in the second mode is performed via the determination of the “Time Over Threshold” (TOT). The possibility of direct per pixel energy measurement presents a substantial advantage for X-ray radiography with polychromatic X-ray sources (tubes) allowing material identification (color X-ray radiography) via analysis of transmission energy spectra recorded by each pixel. The quality of the material recognition is determined by the energy resolution of the detector. The ionization charge generated by the particle is often collected by several adjacent pixels forming a cluster. By proper cluster analysis it is possible to determine not only the particle type but in many cases also direction of its flight.

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