Energy Sciences

The advent of fully coherent free electron laser and diffraction limited synchrotron storage ring sources of x-rays is catalyzing the development of new ultra-high accuracy metrology methods. To fully exploit the potential of these sources, metrology needs to be capable of determining the figure of an optical element with sub-nanometer height accuracy. Currently, the two most prevalent slope measuring instruments used for characterization of x-ray optics are the auto-collimator based nanometer optical measuring device (NOM) and the long trace profiler (LTP) using pencil beam interferometry. These devices have been consistently improved upon by the x-ray optics metrology community, but appear to be approaching their metrological limits. Here, we consider a novel operational mode for the LTP. The fundamental measuring principle of the LTP is reviewed, and a suggested mode of operation is analytically derived. This mode of operation leads to significant suppression of the instrumental systematic errors. Via cross-comparison measurement with the LTP in old and new modes, the performance of the profiler in the new mode is investigated. We also discuss potential areas of further development, including the possibility for local curvature measurement.