Comparison of Goebel Mirrors with Other X-Ray Optics. Mark R. Pressprich, James Phillips, Peter J. LaPuma, Siemens Analytical X-Ray Systems, Inc. 6300 Enterprise Lane, Madison, WI 53719-1173

Goebel mirrors are artificially made X-ray diffracting optics composed of alternating layers of B₄C and W. The bi-layers are several tens of angstroms thick and vary over the length of the mirrors. The ability to vary the bi-layer thickness sets the Goebel mirrors apart from conventional monochromators. An appropriate thickness gradient ensures that the Bragg condition is met at all points along the surface of the optic, a condition not met with a conventional monochromator. Goebel optics are stable over time and produce an intense, monochromatic, highly parallel beam.

Experimental and theoretical comparisons of Goebel mirrors with graphite monochromators and Franks mirrors (reflecting optics) will be presented. Experiments were done with sealed tube (normal focus, fine focus, and long fine focus), and rotating anode sources. Theoretical analysis was done for the same systems with a ray-tracing program and required a full characterization of the source and pinhole collimation in order to reproduce the experiments. The results indicate in particular the importance of the source size and intensity profile as it affects the performance of the Goebel mirrors versus a conventional monochromator.