Bent Laue crystal monochromator for producing areal x-ray beams

A bent Laue crystal monochromator for diffraction of areal monochromatic x-ray beams from a polyenergetic x-ray rotating anode source has been developed at the National Synchrotron Light Source (NSLS). The monochromatic beam, with a solid angle of more than 5 degrees×5 degrees and energy range tunable from 15 keV to 100 keV, is completely separated from the white beam at a distance of less than 1 m from the source. The absolute reflectivity of the monochromator ranges from 10% to 40%, depending on the energy of the x rays being diffracted and on the source size. The energy bandwidth, around 2%, is controllable by varying the diffraction planes used, the crystal thickness, the asymmetry angle and the bending radius. A single emission line from an x-ray tube source can be selectively diffracted into the entire exit-beam solid angle. The monochromator was tested using a compact rotating anode x-ray source at Science Research Laboratory (SRL). The [formula omitted]-alpha characteristic lines (both [formula omitted]-alpha1 and [formula omitted]-alpha2) of cerium and barium targets were diffracted by the monochromator and used for the above and below iodine [formula omitted]-edge imaging of phantoms with several concentrations of iodine contrast agent. Digital subtraction of the images produced an iodine image. The potential applications of the device in clinical radiography are discussed. © 1997, American Association of Physicists in Medicine. All rights reserved.