Design Aspects of X-Ray Grating Interferometry Timm Weitkamp * , Irene Zanette † , Franz Pfeiffer † and Christian David ** * Synchrotron Soleil, Gif-sur-Yvette, France † Department of Physics, Technische Universität München, Garching, Germany ** Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, Villigen, Switzerland Abstract. Considerations are made for the design of X-ray grating interferometers in general and, in particular, for the case of a parallel beam with a high degree of spatial coherence. We specif- ically discuss the properties of different types of gratings and the interdependence of instrument parameters and performance characteristics. Keywords: X-ray phase contrast imaging; Talbot interferometry; phase-shifting interferometry; microtomography; synchrotron radiation; X-ray optics PACS: 87.59.-e, 42.30.Va, 42.79.Dj, 42.30.Ms, 42.87.Bg, 42.25.Fx INTRODUCTION X-ray grating interferometry (XGI) was first demonstrated on synchrotron sources [1–8]. Today, while the implementation of XGI with X-ray tube sources is rapidly progressing, this technique continues to gain importance at synchrotron imaging beamlines, both because of the high density resolution that XGI phase imaging offers and because XGI gives access to multiple imaging modes, including “dark-field” imaging [9], also referred to as “visibility contrast” [10]. While applications in beam diagnostics and X- ray optics characterization exist [11, 12], most of the fixed setups are optimized for imaging applications, and particularly for phase tomography [13–17]. Figure 1 (left) shows the schematic setup of an XGI as first realized by Momose [2]. This device, also known as a Talbot interferometer, consists of two transmission gratings. Instruments of this type are today available at several synchrotron imaging beamlines [18–20]. A third grating can be added to increase the efficiency when an XGI is used at a source of low brilliance [21]. The three-grating setup is usually named a Talbot-Lau interferometer [22]. While it is most often used with laboratory sources, it can also be beneficial at synchrotron sources of limited brilliance, for example at second-generation light sources [23]. The scope of the present article is limited to the two-grating XGI. There are several important figures of merit for an X-ray grating interferometer, in particular the resolution in refraction angle and the spatial resolution of the instrument. These are are related to instrument parameters such as • the pitch of the gratings used; • the length of the instrument, i.e., the distance between G1 and G2; • the sensitivity of the instrument, i.e., the ratio between observed fringe phase and wavefront propagation direction. • the visibility of the fringes observed in moiré mode or in the intensity oscillations in a phase stepping scan, which has a critical influence on the signal-to-noise ratio International Workshop on X-ray and Neutron Phase Imaging with Gratings AIP Conf. Proc. 1466, 84-89 (2012); doi: 10.1063/1.4742273 © 2012 American Institute of Physics 978-0-7354-1072-5/$30.00 84