Progress toward a complete metrology set for the International X-ray Observatory (IXO) soft x-ray mirrors

Lehan, John P.; Atanossova, M.; Chan, Kai-Wing; Hadjimichael, Theodore; Saha, Timo T.; Hong, M.; Zhang, W. W.; Blake, P.

doi:10.1117/12.826625

Cited by 6 publications

(5 citation statements)

References 12 publications

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“…After oxidation, in step 2, the mirror front side is measured by a metrology tool at GSFC, which is an interferometer with a cylindrical null. 16 We have found that the measured surface figure before and after oxidation is unchanged (within 10 nm in RMS height), indicating the integrated stress field in the back side oxide is the same as that on the front side. The surface topology map M 1 measured in step 2 is used as the mirror's initial figure.…”

Section: Processmentioning

confidence: 81%

Progress of coating stress compensation of silicon mirrors for Lynx x-ray telescope mission concept using thermal oxide patterning method

Yao¹,

Chalifoux²,

Heilmann³

et al. 2019

J. Astron. Telesc. Instrum. Syst.

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A thermal oxide patterning method has proven to be effective for correcting coating-stress-induced distortion on flat silicon wafers. We report progress on developing this method for correcting curved silicon mirrors distorted by front-side iridium coatings. Owing to the difference in geometry, a finite element model has been established to calculate the appropriate duty cycle maps in thermal oxide hexagon patterns used for compensation. In addition, a photolithographic process, along with three-dimensional printed equipment, has been developed for creating patterns precisely on the back side of curved mirrors. The developed method has been used to recover the original surface shape of two silicon mirrors which are 100-mm long, 0.5-mm thick, having 312-mm radius of curvature, and 30 deg in azimuthal span (Wolter-I geometry). These mirrors' front sides are sputter-coated by 20-nm iridium layers with ∼-70 N∕m integrated stress. Measurement results show that the developed method can mitigate coating-induced distortion by a factor of ∼5 in RMS height and ∼4 in RMS slope error, corresponding to ∼0.5 arc sec RMS slope error. Residual errors after correction are dominated by midfrequency ripples created during the annealing process, which will be resolved in the future. The presented method is precise and inexpensive and a potential candidate for resolving the coating stress issue for Lynx optics in the future.

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Section: Processmentioning

confidence: 81%

Progress of coating stress compensation of silicon mirrors for Lynx x-ray telescope mission concept using thermal oxide patterning method

Yao¹,

Chalifoux²,

Heilmann³

et al. 2019

J. Astron. Telesc. Instrum. Syst.

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“…Typically, the fabricated mirror segments are 30-degrees wide in the circumferential direction. The mirrors are measured in 3-point, 4-point, or 8-point Cantor Tree mount [2][3][4] .…”

Section: Optical Performance Modelingmentioning

confidence: 99%

“…The IXO project at Goddard Space Flight Center has developed metrology techniques suitable [2][3][4] for the mirror surface metrology of grazing incidence mirrors. For the segmented mirrors of full revolution normal incidence metrology can be used.…”

Section: Introductionmentioning

confidence: 99%

Grazing incidence wavefront sensing and verification of x-ray optics performance

Saha¹,

Rohrbach²,

Zhang³

et al. 2011

SPIE Proceedings

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Evaluation of interferometrically measured mirror metrology data and characterization of a telescope wavefront can be powerful tools in understanding of image characteristics of an x-ray optical system. In the development of soft x-ray telescope for the International X-Ray Observatory (IXO), we have developed new approaches to support the telescope development process.Interferometrically measuring the optical components over all relevant spatial frequencies can be used to evaluate and predict the performance of an x-ray telescope. Typically, the mirrors are measured using a mount that minimizes the mount and gravity induced errors. In the assembly and mounting process the shape of the mirror segments can dramatically change. We have developed wavefront sensing techniques suitable for the x-ray optical components to aid us in the characterization and evaluation of these changes.Hartmann sensing of a telescope and its components is a simple method that can be used to evaluate low order mirror surface errors and alignment errors. Phase retrieval techniques can also be used to assess and estimate the low order axial errors of the primary and secondary mirror segments.In this paper we describe the mathematical foundation of our Hartmann and phase retrieval sensing techniques. We show how these techniques can be used in the evaluation and performance prediction process of x-ray telescopes.

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“…It copies the figure of conventionally fabricated mandrels to cOlllIJlercially procured (Schott D263) thin (-0.4 mm) float glass sheets while preserving their excellent micro-roughness (-4A rms measured over a 300 /lm span). As shown in Figure 2 (right panel), it has been able to make mirror substrates consistently at -6.5 are-seconds (HPD); Each entry in the histogram represents a substrate pair which has been precisely measured with optical metrology [19,20,21,22,23,24] and whose x-ray imaging performance calculated with standard performance prediction techniques. The glass slumping process is capable of making substrates the meet the requirements of a sub-l0 arc-second mirror assembly: It has been used to making the more than 10,000 substrates for the NuST AR mission [7].…”

Section: Technical Approaches and Statusmentioning

confidence: 99%

Next generation astronomical x-ray optics: high angular resolution, light weight, and low production cost

et al. 2012

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X-ray astronomy depends on the availability of telescopes with high resolution and large photon collecting areas. Since x-ray observation can only be carried out above the atmosphere, these telescopes must be necessarily lightweight. Compounding the lightweight requirement is that an x-ray telescope consists of many nested concentric shells, which further require that x-ray mirrors must also be geometrically thin to achieve high packing efficiency. This double lightweight and geometrically thin requirement poses significant technical challenges in fabricating the mirrors and in integrating them into mirror assemblies. This paper reports on the approach, strategy and status of our x-ray optics development program whose objective is to meet these technical challenges at modest cost to enable future x -ray missions, including small Explorer missions in the near term, probe class missions in the medium term, and large flagship missions in the long term.

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Progress toward a complete metrology set for the International X-ray Observatory (IXO) soft x-ray mirrors

Cited by 6 publications

References 12 publications

Progress of coating stress compensation of silicon mirrors for Lynx x-ray telescope mission concept using thermal oxide patterning method

Progress of coating stress compensation of silicon mirrors for Lynx x-ray telescope mission concept using thermal oxide patterning method

Grazing incidence wavefront sensing and verification of x-ray optics performance

Next generation astronomical x-ray optics: high angular resolution, light weight, and low production cost

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