A prototype focusing Laue geometry dual-energy monochromator, designed fro human coronary angiography, has been tested at the National Synchrotron Light Source. The monochromatic photon beams from (111) reflections from two cylindrically bent [100] wafers of silicon were adjusted such that the energy of one of the beams was just above the K edge of iodine and the other beam's energy was just below the edge. Focusing of the beams by the bent crystals was measured with photographic film. An incident beam 4 mm high was focused to a line less than 0.3 mm high at a distance of 3 m. The monochromatic flux was determined by measuring the integrated intensities of a standard Mo powder sample and was excellent agreement with the theoretical estimates. The reflectivity of the crystals was enhanced due to bending by an order of magnitude over the dynamical value.
