Energy-dependent visibility measurements, their simulation and optimisation of an X-ray Talbot-Lau Interferometer

The visibility is a crucial quality parameter in grating-based X-ray phase-contrast imaging as it directly influences the noise of the obtained phase signal. In order to evaluate its behaviour with respect to energy, we used the photon counting semiconductor detector Timepix to obtain a series of measurements at different energy thresholds. These energy-dependent measurements of the visibility response of a Talbot-Lau Interferometer for X-ray phase-contrast imaging are presented in this paper. Furthermore, we report on the results of our effort to model this behaviour in our simulation, where a very good agreement between measurement and simulation could be achieved for two available setups. With this tested workflow we are now able to predict the expected visibility response of a specific setup. This capability is an important prerequisite for the optimisation of an X-ray Talbot-Lau Interferometer. It is predicted that the visibility of our current laboratory setup could be doubled by choosing an appropriate X-ray spectrum or filter material.