Grazing Incidence Synchrotron Radiation Optics—Correlation of Performance with Metrology

Abstract

The performance of grazing incidence x-ray optical systems is severely compromised by arc-second slope errors arising from surface irregularities in the millimeter spatial period range. It is those errors that limit the performance of most of the aspheric optical systems in use at the National Synchrotron Light Source (NSLS) and it is those errors that are most difficult to control during the polishing process. We present here a set of scanning pinhole measurements made on a grazing incidence cylinder mirror which exhibit typical arc-second beam deflections and then correlate these measurements with surface roughness measurements made with a WYKO optical surface profiler. The average power spectral density (PSD) curve for the surface is computed from the profile measurements, and the various bandwidth-dependent statistical quantities, such as RMS roughness and slope error, which are computed from the PSD curve, are compared with the results from the scanning pinhole measurements.