Spectrometric properties of TimePix pixel detector for X-ray color and phase sensitive radiography

Abstract

The semiconductor pixel detector TimePix is a newly developed successor of the Medipix2 device. Each TimePix pixel is provided with preamplifier, discriminator and counter. Discriminators allow full suppression of the noise and selection of energy range of interest. Each counter can be configured to work in one of three principal operation modes: 1. counting of detected particles; 2. measurement of particle energy; 3. measurement of time of interaction. Possibility of per pixel energy measurement presents a substantial advantage for X-ray radiography with polychromatic X-ray sources (tubes). This feature allows to utilize normally not desirable beam-hardening phenomenon for material determination. If the radiographic system is equipped with a microfocus X-ray tube enabling phase sensitive imaging, the spectrometric properties of TimePix bring further advantages as the phase effects are energy dependent. This contribution presents a compact X-ray microradiographic phase sensitive system based on nanofocus X-ray tube and position sensitive single photon counting pixel detector TimePix (256 times 256 square pixels, pitch of 55 mum) with 300 mum thick silicon sensor. The spectral sensitivity of the detector together with the polychromatic nature of the beam allows material determination (color imaging). Moreover, in phase sensitive configuration it is possible to distinguish a transmission (attenuation) image from a phase (refractive) image. Spatial resolution of the system is on the submicrometer level and measuring times in order of seconds.