Sketches of the shear cell in coordinate systems with the z-axis along the X-ray beam, with z = 0 being the sample plane. In (a) a vertical cut through the cell illustrates the design principle, where the dashed line indicates the path of the X-ray beam. The outer part of the shear cell (1, 3, 4, 5) consists of a base plate (4) which holds the front plate (5) via three micrometre screws (1, diameter 2.5 mm, purchased from Owis, Staufen, Germany). The guiding nuts (1a) for the micrometre screws are glued into the base plate with two-component adhesive. Both parts are screwed together with three screws (3, diameter 2.5 mm). Springs (3a) between these screws and the base plate allow the force on the micrometre screws to be controlled. In the inner part of the shear cell (2, 6) two piezo shear actuators (2, purchased from PI Ceramic, Lederhose, Germany) are situated which provide movement of the inner front plate (6) along the x-axis with an amplitude of maximum ±2.5 µm. The Si3N4 membrane windows are glued onto the outer (5) and inner (6) front plate with wax. (b) A cut perpendicular to the beam direction, showing the positioning of the micrometre screws (1), the fixing screws (3), the piezo actuators (2), the outer (5) and inner front plate (6). The black dot shows the hole for the X-ray beam. (c) Position of the shear cell (sample thickness 5–10 µm) in the optical path of the X-ray microscope. Shear is induced by moving one of the two silicon nitride window membranes (inset).