Process-induced inhomogeneities in higher asymmetry angle x-ray monochromators

Korytár, D.; Vagovič, Patrik; Ferrari, C.; Šiffalovič, Peter; Jergel, M.; Dobročka, Edmund; Zápražný, Zdenko; Áč, V.; Mikulı́k, Petr

doi:10.1117/12.2025142

Cited by 3 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The very important parameter of highly asymmetric monochromators as image magnifiers is the crystal surface quality, because the long-range surface undulations 9 deteriorate the final image quality. 8,19 We are also developing the surface processing technologies which can solve the problematic preparation of channel-cut monochromators and consequently allow the production of surfaces of such quality as those prepared by the conventional planar technology. We have applied advanced nanomachining using single-point diamond turning (SPDT) to prepare the crystal surfaces and using several finishing methods including conventional mechanical lapping, chemical polishing, and chemomechanical polishing.…”

Section: Introductionmentioning

confidence: 99%

Calculations and surface quality measurements of high-asymmetry angle x-ray crystal monochromators for advanced x-ray imaging and metrological applications

et al. 2015

View full text Add to dashboard Cite

Abstract. We present the numerical optimization and the technological development progress of x-ray optics based on asymmetric germanium crystals. We show the results of several basic calculations of diffraction properties of germanium x-ray crystal monochromators and of an analyzer-based imaging method for various asymmetry factors using an x-ray energy range from 8 to 20 keV. The important parameter of highly asymmetric monochromators as image magnifiers or compressors is the crystal surface quality. We have applied several crystal surface finishing methods, including advanced nanomachining using single-point diamond turning (SPDT), conventional mechanical lapping, chemical polishing, and chemomechanical polishing, and we have evaluated these methods by means of atomic force microscopy, diffractometry, reciprocal space mapping, and others. Our goal is to exclude the chemical etching methods as the final processing technique because it causes surface undulations. The aim is to implement very precise deterministic methods with a control of surface roughness down to 0.1 nm. The smallest roughness (∼0.3 nm), best planarity, and absence of the subsurface damage were observed for the sample which was machined using an SPDT with a feed rate of 1 mm∕min and was consequently polished using a fine polishing 15-min process with a solution containing SiO 2 nanoparticles (20 nm).

show abstract

Section: Introductionmentioning

confidence: 99%

Calculations and surface quality measurements of high-asymmetry angle x-ray crystal monochromators for advanced x-ray imaging and metrological applications

et al. 2015

View full text Add to dashboard Cite

show abstract

“…The prepared optical elements are to be used for the hard X-ray radiation with the aim to increase diffraction efficiency and intensity throughput either in Laue transmission or Bragg reflection geometry. A perfect surface planarity and reduced roughness is of paramount importance in advanced X-ray metrology or X-ray imaging applications in which the angle of incident or diffracted X-ray beams are very low such as in grazing incidence monochromators or X-ray magnifiers [2,3].…”

Section: Introductionmentioning

confidence: 99%

Nano-machining for advanced X-ray crystal optics

Zápražný¹,

Korytár²,

Jergel³

et al. 2016

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. We present our recent technological achievements in development of the nano-machining of active X-ray crystal optics surfaces. This technique uses a single crystal diamond tool with extremely precise and temperature stabilized positioning system. We can prepare various simple (flat, spherical, cylindrical) as well as more complex freeform surfaces (including aspherical ones). The objective is to prepare high-quality surfaces of the desired shape with subnanometer surface roughness and low sub-surface damage of the crystal lattice. The final surface roughness of a flat Ge surface below 0.4 nm (RMS) was achieved for a very slow regime of the processing using feed rates ≤ 0.25 mm/min. At such a slow feed rate, a parasitic surface grating formed due to rastering the diamond tool along the surface was minimized. Surface roughness Ra was reached well below the level of 3 nm stated by the machining device manufacturer in specifications, which is a very good result. The sub-surface damage varied periodically and followed the surface morphology. Raman peak is shifting to higher phonon frequencies in commercially polished sample as in our sample produced using nano-machining which indicates lower compressive local stresses using our technology. The TEM analysis showed an amorphous layer with thickness of ≈30 nm which origin is the subject of our further research. We would like to emphasize that we do not observe any dislocations in the crystalline phase of germanium (110) laying under amorphous layer. We can conclude from our pilot experiments that the diamond tool nano-machining is a promising technology for high-quality surface treatment to replace less homogeneous chemical methods used in production of X-ray channel-cut crystal optics.

show abstract