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Proceedings Paper

New twist in the optical schematic of surface slope measuring long trace profiler
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Paper Abstract

The advents of fully coherent free electron lasers and diffraction limited synchrotron storage ring sources of x-rays are 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 (PBI). These devices have been consistently improved upon by the x-ray optics metrology community, but appear to be approaching their metrological limits. Here, we revise the traditional optical schematic of the LTP. We experimentally show that, for the level of accuracy desired for metrology with state-of-the-art x-ray optics, the Dove prism in the LTP reference channel appears to be one of the major sources of instrumental error. Therefore, we suggest returning back to the original PBI LTP schematics with no Dove prism in the reference channel. In this case, the optimal scanning strategies [Yashchuk, Rev. Sci. Instrum. 80, 115101 (2009)] used to suppress the instrumental drift error have to be used to suppress a possible drift error associated with laser beam pointing instability. We experimentally and by numerical simulation demonstrate the usefulness of the suggested approach for measurements with x-ray optics with both face up and face down orientations.

Paper Details

Date Published: 7 September 2017
PDF: 17 pages
Proc. SPIE 10385, Advances in Metrology for X-Ray and EUV Optics VII, 103850I (7 September 2017); doi: 10.1117/12.2274400
Show Author Affiliations
Sergey M. Nikitin, Lawrence Berkeley National Lab. (United States)
Gevork S. Gevorkyan, Lawrence Berkeley National Lab. (United States)
Wayne R. McKinney, Diablo Valley College (United States)
Ian Lacey, Lawrence Berkeley National Lab. (United States)
Peter Z. Takacs, Brookhaven National Lab. (United States)
Valeriy V. Yashchuk, Lawrence Berkeley National Lab. (United States)

Published in SPIE Proceedings Vol. 10385:
Advances in Metrology for X-Ray and EUV Optics VII
Lahsen Assoufid; Haruhiko Ohashi; Anand Krishna Asundi, Editor(s)

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