BENT LAUE CRYSTAL MONOCHROMATOR FOR ANGIOGRAPHY AT THE NSLS.

A focusing Laue-geometry dual energy monochromator has been designed for the human coronary angiography project at the National Synchrotron Light Source. The monochromatic photon beams from (111) reflections from two cylindrically bent left bracket 110 right bracket wafers of silicon focus and cross at the patient. The energy of one of the beams is just above the K edge of iodine, used as a contrast agent for the coronary imaging, and the other beam's energy is just below the edge. The reflectivity of the crystals is enhanced due to bending by an order of magnitude over the dynamical value. This advantage is somewhat offset by limiting the vertical aperture in order to maintain a bandwidth of a few hundred eV in the beams. The major advantage of this device should be its low power absorption in the beam from the superconducting wiggler magnet.