Misalignment sensitivity of an inclined crystal monochromator

The sensitivity of a novel inclined crystal monchromator design to misalignments has been calculated, and compared to data. Rocking curve line narrowing as well as broadening can occur because the asymmetry factor of dynamical diffraction given by b= s0·n/sH·n can have an absolute value larger or smaller than unity. Here s0 and sH are the direction cosines of the incident and diffracted beams, respectively, and n is the inward surface normal. An inclined double crystal monochromator which is perfectly aligned would have b =-1 for both crystals, and only then would the diffraction be symmetric. We have computed b and rocking curve linewidths for inclination angles of 70.53 degrees and 85.00 degrees, and we compare these to data for silicon (111) reflections using 8 KeV (CuKα1) radiation. The 70.53 degrees case applies to (11 bar 1) reflection from a (111) oriented crystal. For the 85 degrees case we studied the (11 bar 1) reflection from a specially cut silicon crystal. We report that rotations around the reciprocal lattice vector have the largest affect on b