Acoustically adjustable LiNbO3 double-crystal monochromator for synchrotron radiation

First experiments with the acoustically controlled LiNbO3 double-crystal mo nochromator for synchrotron radiation have been performed on the diffractio n beamline of the Brazilian National Synchrotron Light Laboratory. In order to modify x-ray optical properties of LiNbO3 crystals, 290 MHz surface aco ustic waves were generated with the aid of interdigital transducers, fabric ated on the polished crystal surfaces by using microelectronics technology. It was shown that by the appropriate choice of diffraction planes, the LiN bO3 double-crystal monochromator can be used for both high-flux and high-re solution applications. Surface acoustic waves allow adjustment of an angula r width of diffraction profile to a divergence of the incident synchrotron radiation, optimizing matching conditions for x rays of different wavelengt hs. Diffraction measurements under surface acoustic wave excitation demonst rated that the parameters of the x-ray beam issuing from the monochromatiza tion system are indeed acoustically controlled, providing a 2-2.5-fold broa dening of the diffraction profile and a 1.5-fold gain in the maximum diffra ction intensity. (C) 1999 American Institute of Physics. [S0034-6748(99)046 03-1].