The PEPI (Photon-counting Edge-illumination Phase-contrast Imaging) project is developing a new compact X-ray phase-contrast imaging (XPCI) facility at the INFN laboratories in Trieste (Italy). XPCI performance is enabled by the edge-illumination (EI) technique, whereby an array of beamlets produced by a structured absorbing mask (sample mask) is analyzed either by a second mask or by the detector itself. This arrangement allows the simultaneous detection of attenuation (conventional imaging), phase, and ultra-small-angle scattering USAXS signals, being appealing for biological and material science samples featuring multiple interfaces or a highly granular structure (e.g., pulmonary tissue, additive manufacturing). The setup is suited for samples in the centimeter scale requiring phase/USAXS sensitivity and spatial resolution in the 10 micrometers scale. Thanks to the integration of a photon-counting detector (Pixirad1-PixieIII) with spectral capabilities (2 energy thresholds per pixel) XPCI will be combined with spectral/KES imaging to provide images with lower noise and/or an increased number of decomposition materials.

A Geant4-based simulation framework enabling to simulate refraction (i.e., differential phase-contrast) images in EI mode has been developed.
The simulation features realistic tungsten anode spectra and focal spot distributions, detector energy response, tunable masks (pitch, aperture, thickness), geometry, acquisition modes (double-mask, single-mask, conventional), and movimentation (stepping, dithering). The code of the simulation can be found at this link.