A DOUBLE CRYSTAL MONOCHROMATOR OF SAGITTAL FOCUSING

The double crystal monochromator has been designed, based on the idea of the independent adjustment of crystal positions and orientations, to be able to work in both the fixed beam exit and the variable beam exit cases. The grooved first crystal of the monochromator is cooled directly by water feeding through the rotation axis, and the ribbed second crystal can be bent dynamically to a radius from 1 to 10 meters to perform sagittal focusing by a flexure hinge mechanism. The three degrees of crystal orientations, one for the first crystal and two for the second crystal, can be precisely adjusted in a fraction of arcsecond by flexure hinge mechanisms. The focusing performance of the monochromator has been tested off-line with laser; and the minimum width of 0.6mm for the focusing image has been obtained, which deviates from the theoretical width by 0.12mm and gives a bending radius resolution better than 0.25%.