X-ray Optics

Flat and curved multilayer X-ray optics can be used as monochromators, collimators or focussing optics in X-ray diffraction, X-ray reflectometry, X-ray fluorescence analysis and for synchrotron applications. Several types of multilayer X-ray optics can be designed depending on the customers application.

Parallel Beam X-ray Optics

Parallel beam X-ray optics are optical components with a graded multilayer deposited on a substrate having a parabolic shape in beam direction. These optical devices convert (in one dimension) a divergent incoming beam into a parallel one, or vice-versa an incoming parallel beam into a focusing one.

In order to obtain high efficiency, the d-spacing of the multilayer has to be varied from the front end to the rear end of the optics in correspondence to the aspheric curvature. Either the X-ray source or the detector (or detector slit) may be placed at the optics focal distance, for primary or secondary side applications, respectively.

High precision parallel beam optics on bended wafer piece (left) and on prefigured substrate (right).

Spectral lines	Cr, Co, Cu, Ga, Mo, Rh, Ag, In (others on request)
Mean Reflectivity	R > 70%
Monochromaticity	Kα₁+Kα₂ or Kβ
Divergence	Δφ < 0.03° (for 40 μm source width)
Mirror length	L = 40...100 mm (on customers' request)
X-ray source type	line focus
Parallel beam width b	dependent on mirror length, geometry and X-ray wavelength, typical values: 1.5 mm (Cu-K, L = 60 mm), 1.0 mm (Mo-K, L = 100 mm)
Typical focal length (source - mirror center)	x_m = 100..110 mm (others possible)

Focusing X-ray Optics

Focusing X-ray optics convert a divergent incoming beam into a focusing one. Having an elliptical figure of curvature the d-spacing of the multilayer coating has to be changed from the front end to the rear end of the optics. The primary and secondary foci of the mirror are located in the two focal points of the ellipse which typically coincide with the X-ray source point and the sample or detector position.

Generation of a monochromatic focusing beam in one dimension

Beam path and main parameters of focusing X-ray optics

Spectral lines	Cr, Co, Cu, Ga, Mo, Rh, Ag, In (others on request)
Mean Reflectivity	R > 70%
Mirror length	L = 40 mm ... 100 mm (on customers' request)
X-ray source type	line focus
Focal line width b	depending on spectral line, geometry and mirror length typically few tens of µm
Typical focal lengths (source - mirror center - focus)	f_1/2 = 100..2500 mm (others possible, primary and secondary side can be chosen independently)

ASTIX-c: 2-dimensionally collimating

ASTIX-c mirrors are 2-dimensionally collimating X-ray optics in a modified Montel geometry (1) for the generation of 2-dimensional high intensity parallel X-ray beams.

Working principle of ASTIX-c collimating geometry

Parallel beam profile for Mo Kα radiation, I>10⁷ cps (low power µ-source), b² ≈ 1 mm²

High precision vacuum mirror housings for ASTIX optics

Spectral lines	Cr, Co, Cu, Ga, Mo, Rh, Ag, In (others on request)
Typical lengths	60 mm - 150 mm
X-ray source type	all typical types of X-ray sources (rotating and fixed anodes, liquid metal jet and micro focus X-ray tubes)
Typical parallel beam size	1 mm² ≤ b² ≤ 5 mm²
Typical focal length (source - mirror center	f₁ = 100..110 mm (others possible)
Accessories	High precision vacuum mirror alignment housing

ASTIX-f: 2-dimensionally focusing

ASTIX-f mirrors are 2-dimensionally focusing X-ray optics in a modified Montel geometry (1) for the generation of high intensity focused X-ray beams. They can be optimized either for high flux or high resolution.

High Flux (HF) Optics

high photon flux at sample position
high integrated pixel intensity

High Resolution (HR) Optics

small spot size at sample position
high lateral resolution in the detector plane

(1) M. Montel - "The X-Ray Microscope with Catamegonic Roof-Shaped Objective" in: X-ray Microscopy and Microradiography, Vol.5, 1957,pp 177 - 185

Profile of the diffracted beam between optics and focal point (f₂ = 310 mm)

Spectral lines	Cr, Co, Cu, Ga, Mo, Rh, Ag, In (others on request)
Typical lengths	60 mm - 150 mm
X-ray source type	all typical types of X-ray sources (rotating and fixed anodes, liquid metal jet and micro focus X-ray tubes)
Typical focal spot sizes	<30 µm .. 500 µm
Typical focal lengths (source - mirror center	f_1/2 = 100..500 mm (others possible)
Accessories	High precision vacuum mirror alignment housing

Flat Graded X-ray Optics

Flat graded X-ray optics are mirrors with an artificial multilayer coating showing a lateral thickness gradient along the substrate length. They monochromatize the incoming beam while leaving the divergence unchanged, i. e. they generate a divergent monochromatic beam. In order to obtain high efficiency, the d-spacing of the multilayer has to be changed from the front end to the rear end of the mirror. Flat graded optics require a plane substrate and have a single focal point (line). Either the X-ray source or the detector (or detector slit) may be placed at the optics focal distance, for primary or secondary side applications, respectively.

Generation of a monochromatic 1-dimensional divergent beam

Beam path and main parameters of a flat graded multilayer

Spectral lines	Cr, Co, Cu, Ga, Mo, Ag (can be used for different wavelengths)
Mean Reflectivity	R > 70%
Monochromacy	Kα₁+Kα₂
Mirror length	L = 20 mm ... 80 mm (on customers' request)
X-ray source geometry	line focus preferred
Capture angle	φ=0.20° (L = 20 mm) ... φ=0.50° (L = 80 mm) for Cu Kα
Application	monochromator (primary or secondary) in Bragg-Brentano geometry

Monochromators and synchrotron mirrors

Monochromators are optical devices with a multilayer of constant period thickness over the substrate length in order to obtain high efficiency. A plane figure is usually required for such monochromators. Depending on the application either high resolution or high flux multilayer monochromators can be fabricated.

Download: Synchrotron optics prospectus (pdf)
Download: Tender X-ray optics prospectus (pdf)

Spectral range	<50 eV - 100 keV
Material systems	optimized on wavelength or on customer's request
Typical sizes	500 mm length or 8 inches diameter
Resolution	0.25% < ΔE/E < 3% (periodic multilayers) ΔE/E > 5% on request (aperiodic multilayers)
Thickness homogeneity	Δd/d < 0.02%
Applications	monochromators for laboratory X-ray sources and for synchrotrons, optimized for high reflectivity or tailored resolution polarizers in the soft X-ray range (O-K, Fe-L, Ni-L)

Broadband Mirrors / Depth-Graded Multilayers

Tailored multilayers with large number of different bilayer thicknesses to fulfill Bragg’s law for many photon energies / wavelengths
Broadband or bandpass reflectors possible
Energy bandwidths of 20% and more feasible
Can be optimized for photon energies from EUV up to hard X-rays (80 keV and more)
Selected bandwidth is maintained even if energy and corresponding incidence angle are changed
Adaptation of the energy band to the source spectrum possible
Large photon flux due to the collection of a large portion of the source spectrum e.g. at bending magnets