A novel instrument for generating angular increments of 1 nanoradian

Alcock, Simon G.; Bugnar, Alex; Nistea, Ioana; Sawhney, Kawal; Scott, Stewart M.; Hillman, Michael; Grindrod, Jamie; Johnson, Iain

doi:10.1063/1.4937352

Cited by 12 publications

(15 citation statements)

References 16 publications

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“…The Diamond nano-angle generator (NANGO) 52 is used to calibrate the linearity of the SAM system. The NANGO angle is varied with a constant step size of 10nrad, and the speckle images were recorded by SAM.…”

Section: Methodsmentioning

confidence: 99%

Nano-precision metrology of X-ray mirrors with laser speckle angular measurement

2021

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X-ray mirrors are widely used for synchrotron radiation, free-electron lasers, and astronomical telescopes. The short wavelength and grazing incidence impose strict limits on the permissible slope error. Advanced polishing techniques have already produced mirrors with slope errors below 50 nrad root mean square (rms), but existing metrology techniques struggle to measure them. Here, we describe a laser speckle angular measurement (SAM) approach to overcome such limitations. We also demonstrate that the angular precision of slope error measurements can be pushed down to 20nrad rms by utilizing an advanced sub-pixel tracking algorithm. Furthermore, SAM allows the measurement of mirrors in two dimensions with radii of curvature as low as a few hundred millimeters. Importantly, the instrument based on SAM is compact, low-cost, and easy to integrate with most other existing X-ray mirror metrology instruments, such as the long trace profiler (LTP) and nanometer optical metrology (NOM). The proposed nanometrology method represents an important milestone and potentially opens up new possibilities to develop next-generation super-polished X-ray mirrors, which will advance the development of X-ray nanoprobes, coherence preservation, and astronomical physics.

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Section: Methodsmentioning

confidence: 99%

Nano-precision metrology of X-ray mirrors with laser speckle angular measurement

2021

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“…There were suggested a number of calibration methods that are specific to the particular measurements. [47][48][49] The drawback of the dependence of the systematic errors on the specific measurement arrangement can be advantageous if people use the correlation method for suppression of systematic errors of slope profilers, as suggested in Ref. 25 The reliability and efficiency of the calibration of a slope profiler can be significantly improved by using the SUT as a reference mirror (self-reference) when calibrating the profiler, avoiding the need for a universal multi-dimensional calibration, accounting for all possible shapes of SUTs.…”

Section: Ltp Systematic Errorsmentioning

confidence: 99%

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

Nikitin

Gevorkyan²,

McKinney

et al. 2017

Advances in Metrology for X-Ray and EUV Optics VII

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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.

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“…Even so, the measurement accuracy is limited by the instrument's inherent systematic errors, which often are on the level of 1-2 µrad over the roughly 10 mrad dynamic measurement range. This has made vital the development of a variety of comprehensive and ingenious calibration methods for suppression of the systematic errors [24][25][26][27][28][29][30][31]. However, with the systematic error dependent on the peculiarities of the experimental set-up and the shapes and sizes of the optics under test [32], accurate calibration of the instruments is an arduous task.…”

Section: Introductionmentioning

confidence: 99%

Multifunctional light beam source for surface slope measuring long trace profilers

Yashchuk

Lacey

Anderson

et al. 2020

Advances in Metrology for X-Ray and EUV Optics IX

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To fully exploit the advantages of fourth-generation synchrotron light sources, diffraction-limited-storage-rings (DLSR) and fully coherent free electron lasers (FELs), beamline mirrors and diffraction grating must be of exceptional quality. To achieve the required mirror and grating quality, the metrology instrumentation and methods used to characterize these challenging optics and, even more so, optical assemblies must also offer exceptional functionality and performance. One of the most widely used slope measuring instruments for characterizing x-ray optics is the long trace profiler (LTP). The easily reconfigurable mechanical design of the LTP allows optimization of the profiler arrangement to the specifics of a particular metrology task. Here, we discuss the optical schematic, design, and performance of an original multifunctional light beam source that provides functional flexibility of the LTP optical sensor. With this source, the LTP can be easily reconfigured for measurements of x-ray mirrors or diffraction gratings that have widely different source coherence requirements. Usage of a source with a low degree of coherence for mirror metrology helps to suppress the LTP systematic errors due to spurious interference effects in the LTP optical elements. A high-coherence narrow-band source is used for groove-density-distribution characterization of x-ray diffraction gratings. The systematic error and spatial resolution of the LTP with the different sources is also measured and analyzed.

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A novel instrument for generating angular increments of 1 nanoradian

Cited by 12 publications

References 16 publications

Nano-precision metrology of X-ray mirrors with laser speckle angular measurement

Nano-precision metrology of X-ray mirrors with laser speckle angular measurement

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

Multifunctional light beam source for surface slope measuring long trace profilers

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