A tunable x-ray waveguide used to funnel x-rays from a synchrotron source to a sample. X-rays from the left enter the guide consisting of two plates. The upper plate is positioned to be parallel to the lower plate to within 2nm by using an interferometer technique based on a principle called "fringes of equal chromatic order" (FECO). The distance between the plates determines which xray modes will be transmitted.
Courtesy of J.F. van der Veen, University of Amsterdam.
This research is reported by M. J. Zwanenburg et al. in the 22 February 1999 issue of Physical Review Letters.