The experimental procedure consisted of placing a periodic object into the x-ray beam at a known distance from the source and measuring the contrast in images taken at specific distances from the object.

The object was a phase grating with a sinusoidal profile and a grating period a of 6.35 micrometers. It was placed at a distance of 55 m from the source. The images were taken at D0= DT/ 4 and D1= 3DT/ 4, where DT is the Talbot distance.

When using an x-ray energy of 17.5 keV, the half-Talbot distance is DT /2 = a2/lambda ~ 57 cm.


The figure below shows such images obtained with the grid mounted vertical. The same procedure was repeated with the grating lines placed horizontally.

Figure: Images taken at DT/4 et 3DT/4 with the grid mounted vertical. The x-ray energy was set to 17.5 keV.


Assuming a source with a Gaussian shape, the angular source dimensions were calculated using the following expression:


From the values obtained (sV= 1.4 µrad, sH= 4.9 µrad) we derive a vertical source size of 79 µm and a horizontal source size of 269 µm.


*For more details, please, contact one of the following authors: J.P. Guigay, P. Cloetens, P. Rejmankova, J. Baruchel, V. Mocella, and S. Zabler.


More information on the technique can be found in: "Fractional Talbot imaging of phase gratings with hard x-rays", P. Cloetens, J.P. Guigay, C. De Martino, J. Baruchel, M. Schlenker, Optics Letters, Vol. 22, 14, 1059-61 (1997)