MODIFICATIONS TO THE 1989 SHADOW RAY-TRACING CODE FOR GENERAL ASYMMETRIC PERFECT-CRYSTAL OPTICS

The dynamical theory of the diffraction of X-rays from perfect crystal s is traditionally expressed in terms of Maxwell's equations using a s emi-classical theory originally due to Ewald and Von Laue. Combining t he work of Batterman and Cole, Caticha and Caticha-Ellis, and Zacharia sen, one can obtain a formalism that treats the general asymmetric, th ick and thin crystal, Laue and Bragg cases within the second-order dis persion surface approximation with no assumptions concerning the centr o-symmetry of the crystal lattice. We have implemented this formalism with the thick-Bragg-crystal E-field boundary-value conditions in seve ral routines we have added to one of the Advanced Photon Source's modi fied copies of the 1989 VAX/VMS version of the SHADOW ray-tracing code in order to allow us to ray trace distorted inclined double-crystal m onochromators and high-resolution backscattering analyzers.