X-RAY ANGLE INTERFEROMETRY - A PRACTICAL SET-UP FOR CALIBRATION IN THE MICRORAD RANGE WITH NANORAD RESOLUTION

X-ray interferometry-is a crystallographic diffraction technique utili zing a moire effect generated by the lattice. If almost perfect silico n single crystals are employed, scanning of the periodic moire can be used for the calibration of translation or rotation on a nanometric sc ale since the lattice parameter is well known in terms of the SI unit of length. A monolithic x-ray angle interferometer consisting of two c rystal blocks and a connecting flexure spring allowing relative rotati on was manufactured. Each block supports two x-ray optical lamellae. T heir optimum thickness for good visibility of the angular moire fringe s during rotation was calculated using the dynamical theory of x-ray d iffraction. The main block serves as the base of the interferometer an d also incorporates the piezoelectric drive. This arrangement of three bimorph actuator blades allows angular scanning through the zero degr ee position in order to use the full Bragg reflection width. Pre-tensi oning of the flexure spring, balancing of the rotating part and angula r scanning are possible simultaneously. Different operating modes, fre e-running and locked to the fringe slope, were tested. This very compa ct device can be used as a stand-alone instrument or as a fine scale i n a large angle measuring calibrating facility.