EP2175456A2 - X-ray analysis instrument with mobile aperture window - Google Patents

Abstract

The X-ray analysis instrument has an X-ray source that emits an X-ray beam. A collimator mechanism has an aperture window with an aperture opening (3) through which X-ray beam is passed. The gradual movement of the aperture window is performed along a direction transverse to the X-ray beam. The path of movement of aperture window is larger than the extension of the X-ray beam along preset direction. An independent claim is included for method for operating X-ray analysis instrument.

Description

• eine Röntgenquelle, welche einen Röntgenstrahl emittiert,
• eine Röntgenoptik, insbesondere einen Multischicht-Röntgenspiegel,
• und eine Blendenmechanik, wobei die Blendenmechanik ein Aperturfenster mit einer Aperturöffnung ausbildet, durch welche zumindest ein Teil des Röntgenstrahls tritt.

The invention relates to an X-ray analysis instrument, in particular X-ray diffractometer, comprising

• an x-ray source emitting an x-ray beam,
• an X-ray optics, in particular a multi-layer X-ray mirror,
• and an aperture mechanism, wherein the aperture mechanism forms an aperture window with an aperture opening through which at least a portion of the x-ray beam passes.

Such a Röntgenanalyseinstrument has become known for example by the DE 10 2004 052 350 A1 ,

X-ray diffraction is an efficient method for non-destructive chemical analysis of especially crystalline samples. In modern X-ray diffractometers, the X-ray generated by an X-ray source is directed onto a specimen via a multilayer optic, and the diffracted X-ray is analyzed by a detector.

With multi-layer X-ray optics, monochromatization and, above all, beamforming of the X-ray beam in an X-ray analysis apparatus are performed with good efficiency. However, the structure of the multilayer X-ray optics also determines the beam properties on the output side of the multilayer optics. Physical quantities such as the input and output convergence, the focal lengths between source and image focus, and the magnification ratio and thus also the size of the X-ray beam in the image focus must be established prior to the production of the multilayer optics. In particular, it is not possible subsequently to vary the surface curvature of a multilayer X-ray mirror or the layer spacings in its multilayers. As a result, multilayer X-ray optics are basically inflexible.

A particularly important property in X-ray diffractometry is the convergence angle β, since the resolution of a diffractometer decreases with increasing convergence angle. To adapt to changing measurement requirements convergence diaphragms have become known.

The DE 10 2004 052 350 A1 describes several holes of the same diameter on a rotatably mounted disc of an X-ray analyzer, with which a diaphragm function is achieved. By slightly turning the disc, a shutter can be moved continuously in a first direction, and by changing to another hole on a different radius of the disc, a diaphragm can be moved in discrete steps in a second direction. There are several holesets with different hole diameters. Similar functionality can be achieved with a multi-hole tape.

From the US 7,245,699 B2 is a Montel optics with a fixed thereto variable diaphragm, comprising two L-shaped diaphragm sections, one of which is movable along the bisector between the two mirror surfaces known.

In both cases, the possibilities of beam conditioning are limited. The perforated disc of DE 10 2004 052 350 A1 allows only a stepped adjustment of the beam divergence (corresponding to the hole diameter of the different sets of holes) and in one direction only a stepped aperture shift; Moreover, the mechanical structure is very complex here. The aperture mechanics of US 7,245,699 B2 always always fades out a source-distant part of the X-ray radiation.

Object of the present invention

It is the object of the present invention to provide an X-ray analysis instrument in which there is a greater breadth of possible beam conditioning, so as to improve the possible uses of multi-layer X-ray optics.

Brief description of the invention

This object is achieved by an X-ray analysis instrument of the aforementioned type, which is characterized
that the diaphragm mechanism means for stepless method of Aperture window in at least one direction transverse to the X-ray beam comprises that the aperture opening is at least as large as the cross section of the X-ray beam at the location of the aperture window,
and that the path of the aperture window accessible through the aperture mechanism in the at least one direction is at least twice as large as the extent of the x-ray beam at the location of the aperture window in this direction.

With the diaphragm mechanism according to the invention, it is possible with the aperture opening with respect to the area ratio to select any portion of the X-ray beam cross section at the location of the aperture window and to supply it to a subsequent X-ray experiment. To adjust the proportion of the X-ray beam cross section, the aperture opening is correspondingly proportionally overlapped with the X-ray beam cross section. If the full beam cross section is desired, the aperture opening is brought into complete overlap with the X-ray beam cross section; since the aperture opening is at least as large as the X-ray beam cross-section, the X-ray beam is in no way shaded.

Due to the wide mobility of the aperture window, a partial region of the X-ray cross section can be selected from two opposite sides. In general, the X-ray beam has different properties in different regions of its cross-section, so that the properties of the transmitted X-ray component can also be selected in a simple manner by means of the diaphragm mechanism according to the invention. In the case of an aperture opening which is larger than the X-ray beam, preferably in the at least one direction VW> = AOE + RS, with VW: travel path of the aperture window; AOE: extension of the aperture opening; RS: extension of the X-ray.

Preferably, the at least one direction, in which the aperture window can be moved steplessly and over at least twice the beam extent, extends from the source-near to the source-distant portion of the X-ray beam cross section. As a result, particularly relevant properties of the transmitted X-ray beam can be influenced.

Particularly preferred is an embodiment of the X-ray analysis instrument according to the invention, which provides that the diaphragm mechanism comprises means for continuously moving the aperture window in two independent directions transverse to the X-ray beam,
and that the respective path of the aperture window accessible by the shutter mechanism in each of the independent directions is at least twice as large as the extent of the x-ray beam at the location of the aperture window in the respective independent direction.

The diaphragm mechanism in the design with two independent traversing directions (adjustment possibilities) allows an even larger, almost arbitrary selection of a contiguous subsection of the cross section of an X-ray beam. For this purpose, the aperture opening, which is at least as large as the extent of the x-ray beam, is brought into overlap with the x-ray beam only to the extent that the cross-section of the x-ray beam is to enter the subsequent x-ray experiment (typically the irradiation of a sample).

In most positions of the aperture window, therefore, only part of the aperture opening is irradiated by X-ray radiation, and the remaining part of the aperture opening is illumi- nated. Around the aperture opening, the aperture window has a sufficiently wide shading frame from which the portion of the x-ray radiation that does not pass through the aperture opening is completely shadowed.

In a centered (or completely open) movement position of the aperture window, however, the entire X-ray beam can pass through the aperture window, since the aperture (if appropriate after setting the window size, if this is adjustable) is greater than or at least equal to the extent of the X-ray beam at the location of the aperture window.

The trajectory of the aperture window in the embodiment with two independent traversing directions is sufficiently large so that each point on the edge of the aperture stop can be overlapped with any point on the edge of the X-ray beam cross section (at the aperture window location). As a result, a partial region of the beam cross section of the X-ray beam can be selected from any direction. According to the invention, at least VW> = 2 * RS applies in the two independent directions, with VW: traversing path of the aperture window, and RS: extension of the X-ray beam. In the case of an aperture opening which is larger than the X-ray beam, preferably also in each of the independent spatial directions VW> = AOE + RS, with AOE: extension of the aperture opening.

Due to the infinitely movable diaphragm mechanism, the area of the selected (transmitted) portion of the X-ray beam cross section is also infinitely variable. Within the scope of the invention, this subarea can be selected arbitrarily between 0% and 100% of the X-ray beam cross-section with an area fraction. Note that for this stepless selection of the subregion, a fixed, unchangeable aperture size can be maintained.

In the context of the invention, the selection of a specific subarea of an X-ray beam is carried out in particular to improve the data quality in an X-ray diffractometric measurement, in particular a signal-to-noise ratio. The selection of an optimal subarea can in particular by means of ray tracing methods taking into account the properties of the (multilayer) X-ray optics in a simulation, in particular wherein the distribution of the X-ray flux density over the cross section of the X-ray beam is calculated, and the effects of selecting different subregions of the cross section for the intensity distribution in a detection level is determined.

The at least one direction or the two independent directions are preferably at least approximately perpendicular to the propagation direction of the X-ray beam; Preferably, the two independent directions are still at least approximately perpendicular to each other. The "location of the aperture window" refers to the position with respect to the propagation direction of the X-ray beam.

Further, preferred embodiments of the invention

In a preferred embodiment of the X-ray analysis instrument according to the invention, the size of the aperture opening is not adjustable. An aperture window with fixed aperture opening has a particularly simple and therefore cost-effective design.

In an alternative, advantageous embodiment of the diaphragm mechanism, the size of the aperture opening is adjustable, wherein the aperture opening is adjustable to a size which is at least as large as the cross section of the X-ray beam at the location of the aperture window. Other selectable sizes of the aperture window are then typically smaller than the cross-section of the x-ray beam. In this embodiment, there is an even greater freedom in the selection of the portion of the cross section of the X-ray beam; In particular, subregions in the interior of the cross section (ie subregions without edge portion) can be selected.

In a preferred embodiment of this embodiment, the aperture mechanism for adjusting the size of the aperture opening on two mutually movable, L-shaped Aperturteilstücke. This simple structure has proven itself in practice.

Also preferred is an embodiment of the X-ray analysis instrument according to the invention, in which the diaphragm mechanism is arranged on the output side of the X-ray optics. As a result, the beam geometry, in particular a beam convergence on an illuminated sample, can best be controlled.

Particularly preferred is an embodiment, which provides that the aperture window has a square aperture opening, that the X-ray beam at the location of the aperture stop has an approximately square cross section, wherein the side edges of the square aperture opening and the square cross section of the X-ray beam are oriented parallel to each other, and that at least one direction in which the aperture window is movable, along a diagonal of the square aperture opening is oriented. In this case, by methods along only one diagonal, effectively a square portion of the X-ray beam can be varied in size. Also, the beam quality often varies particularly greatly toward the corner regions of a square X-ray beam cross section, and the above device of the travel paths makes these corner regions particularly easily accessible. Preferably, the at least one direction runs along the diagonal of the X-ray cross section, along which the source-near to the source-distant portion of the X-ray beam is passed. With two independent traversing directions, these typically run on the two diagonals of the square X-ray cross section.

Also preferred is an embodiment, which is characterized in that the X-ray optics are arranged in a gas-tight optical housing and the diaphragm mechanism in a gas-tight diaphragm housing, wherein the two housings are evacuated or are flooded with a protective gas,
or that the X-ray optics and the diaphragm mechanism are arranged in a common, gas-tight housing, wherein the common housing is evacuated or flooded with a protective gas. In both cases, the protective gas can reduce corrosion and soiling on the surfaces of the X-ray optics and the diaphragm mechanism as well as the air absorption.

Also advantageous is an embodiment in which the means for continuous movement of the aperture window comprise at least one micrometer screw and / or at least one fine-threaded bolt. These agents have proven themselves in practice. The micrometer screw is particularly suitable for a direction to be adjusted frequently.

In a further advantageous embodiment, it is provided that the diaphragm mechanism has a holder for a replaceable aperture window element, and that the holder can be moved by the means for stepless movement of the aperture window. As a result, the X-ray analysis device is easily adaptable to different requirements, in particular local expansions of the X-ray beam.

An X-ray analysis instrument according to the invention can be used, in particular in X-ray diffractometry, to select a portion of the X-ray beam to direct reflection separation by means of the aperture opening of the aperture window and to direct it to a sample. With the X-ray analysis device according to the invention, the selection of the proportion (or partial area) is targeted and at the same time particularly simple and flexible.

The scope of the present invention also includes the use of a diaphragm mechanism comprising an aperture window with an aperture opening for selecting a portion of an X-ray beam, wherein the X-ray beam is emitted by an X-ray source and imaged onto a sample by X-ray optics, in particular a multi-layer X-ray mirror in particular wherein this use takes place with an X-ray analysis instrument according to the invention,
characterized in that for adjusting, in particular reducing, the focus size of the X-ray beam at the location of the sample by means of the aperture opening of the aperture window, a proportion of the X-ray beam remote from the X-ray optics is selected. In the context of the present invention it has been found that a source-remote portion of an X-ray beam can give better data quality, in particular a better signal-to-background ratio in X-ray experiments, especially in X-ray diffraction experiments on smaller samples compared to the total X-ray beam at the sample location. In particular, scattering in air, sample holder or other parts of the X-ray analysis instrument can be reduced by an optimized focus size. The selected, distant portion of the X-ray beam extends with its cross-sectional area at the location of the aperture window in the case of a single reflection on the X-ray optics (such as a Göbelspiegel) according to the invention to a maximum of the center line of the cross section of the entire X-ray beam, said center line, the X-ray beam at the location of the aperture window divided into a (with respect to the reflection at the X-ray optics) near the source and a source distant half, each with the same area proportions. In the case of a double reflection on the X-ray optics (such as a Monteloptik) according to the invention extends the selected, distant source portion of the X-ray to a maximum of the two centerlines of the cross section of the entire X-ray beam, said center lines of the X-ray at the location of the aperture window in each case (with respect the respective reflection on the X-ray optics) divide source-near and source-distant half, each with the same area proportion; with others Words, the selected, distant from the source portion of the X-ray is then in that area (typically "quarter") of the X-ray cross section, with respect to which both reflections are attributable to the X-ray optics of the source distant side. The off-center portion of the X-ray comprises, in the case of a single reflection, 50% or less, and preferably 40% or less, of the cross-sectional area of the entire X-ray. In the case of dual reflection, the off-center portion of the X-ray beam typically comprises 25% or less, and preferably 20% or less, of the cross-sectional area of the entire X-ray beam.

In a preferred variant of the use according to the invention, the focus size of the X-ray beam at the location of the sample is set to the size of the sample. By (possibly) complete illumination of the sample, but also only the sample, the signal-to-background ratio can be optimized. The adjustment of the focus size is effected in particular by the relative positioning of the aperture opening to the X-ray beam with respect to source proximity and source distance (ie transversely to the propagation direction of the X-ray beam), whereby the focus size at the sample location can be adjusted even if the size of the aperture opening or the same area of the selected beam cross section is invariable ,

In an advantageous variant of the use according to the invention, the selected portion of the X-ray beam distant from the source has a below-average mean photon flux density compared to the rest of the X-ray beam. Surprisingly, in some cases, despite a lower average flux density in the selected portion than in the rest (or in the total) X-ray, an improvement of the reflection separation or the signal-to-background ratio is possible, compared with, for example, the use of a source-proximate portion with regularly larger average Flux density than the rest (or in the whole) X-ray. The average flux density in a selected portion of the x-ray beam is determined over the total (integrated) photon flux in the selected portion divided by the cross-sectional area of the selected portion; the same applies to the rest of the x-ray beam.

A variant of use is also preferred in which the aperture window is positioned so that no X-ray radiation passes through part of the aperture opening of the aperture window. In other words, only part of the aperture opening is held in the X-ray beam (or overlapped with the X-ray beam). As a result, a portion of an X-ray beam cross-section, which is smaller than the aperture opening, can be selected for transmission with little effort even with a large aperture opening.

Finally, a variant of use is also preferred in which the aperture window is arranged in the X-ray beam between the X-ray optics and the sample. As a result, in turn, the beam geometry, in particular a beam convergence on the illuminated sample, can be well controlled.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, according to the invention, the above-mentioned features and those which are further developed can each be used individually for themselves or for a plurality of combinations of any kind. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Detailed description of the invention and drawing

Fig. 1

eine schematische Darstellung der Strahlgeometrie im Bereich einer Multischicht-Röntgenoptik;

Fig. 2

ein Strahlprofil senkrecht zur Ausbreitungsrichtung eines Röntgenstrahls ausgangsseitig einer Monteloptik, berechnet mittels ray-tracing;

Fig. 3

das Strahlprofil von Fig. 2, mit einem eingeschobenen Aperturfenster eines erfindungsgemäßen Röntgenanalyseinstruments, mit zentrierter Aperturöffnung;

Fig. 4

das Strahlprofil von Fig. 3, mit in diagonaler Richtung A verschobener Aperturöffnung;

Fig. 5

das Strahlprofil von Fig. 3, mit in diagonaler Richtung B verschobener Aperturöffnung;

Fig. 6

Diagrammdarstellung der Fokusgröße als Funktion des Photonenflusses für verschiedene Verfahrpositionen des Aperturfensters von Fig. 3;

Fig. 7

Diagrammdarstellung des Photonenflusses als Funktion der Strahldivergenz für verschiedene Verfahrpositionen des Aperturfensters von Fig. 3;

Fig. 8

Diagrammdarstellung der Photonenflussdichte als Funktion des Photonenflusses für verschiedene Verfahrpositionen des Aperturfensters von Fig. 3;

Fig. 9

eine schematische Darstellung einer vollständig montierten Blendenmechanik eines erfindungsgemäßen Röntgenanalyseinstruments, in Vorderseitenansicht;

Fig. 10

eine schematische Darstellung der Blendenmechanik von Fig. 9 in schräger Rückansicht;

Fig. 11

eine schematische Darstellung der Blendenmechanik von Fig. 9, jedoch ohne Gehäuse und Verstellschrauben;

Fig. 12

eine schematische Darstellung der Blendenmechanik von Fig. 9, jedoch ohne Gehäuse, aber mit Verstellschrauben;

Fig. 13

eine schematische Darstellung eines austauschbaren Apertur-Fenster-Elements in einer Halterung (Blendenaufnahme) für die Erfindung, in Aufsicht;

Fig. 14

die Halterung von Fig. 13 mit herausgenommenem Aperturfenster-Element, in schematischer Schrägansicht;

Fig. 15a, 15b

schematische Aufsichtsdarstellungen auf eine Blendenmechanik mit verstellbarer Größe der Aperturöffnung für die Erfindung, mit zwei verschiedenen, eingestellten Fenstergrößen;

Fig. 16

Baugruppe umfassend eine Blendenmechanik in einem Blendengehäuse und eine Röntgenoptik in einem mit dem Blendengehäuse zusammengebauten Optikgehäuse, für die Erfindung, in schematischer Schrägansicht;

Fig. 17a-17b

experimentell ermittelte Beugungsmuster von einem kleinen Thaumatinkristall, mit einem Strahl mit Fokusgröße am Probenort von 0,25 mm (Fig. 17a) und mit einem Strahl mit erfindungsgemäß verkleinerter Fokusgröße am Probenort von 0,12 mm (Fig. 17b);

Fig. 18a

eine schematische Darstellung eines erfindungsgemäßen Röntgenanalyseinstruments;

Fig. 18b

eine schematische Querschnittsdarstellung zu Fig. 18a senkrecht zur Strahlausbreitungsrichtung am Ort des Aperturfensters;

Fig. 19a-19c

eine schematische Darstellung verschiedener Verfahrpositionen eines Aperturfensters relativ zu einem Röntgenstrahl, zur Illustration der erfindungsgemäßen Verfahrwege des Aperturfensters.

The invention is illustrated in the drawing and will be explained in more detail with reference to embodiments. Show it:

Fig. 1

a schematic representation of the beam geometry in the range of a multi-layer X-ray optics;

Fig. 2

a beam profile perpendicular to the propagation direction of an X-ray beam on the output side of a Monteloptik, calculated by means of ray-tracing;

Fig. 3

the beam profile of Fig. 2 with an inserted aperture window of an X-ray analysis instrument according to the invention, with centered aperture opening;

Fig. 4

the beam profile of Fig. 3 with aperture aperture shifted in the diagonal direction A;

Fig. 5

the beam profile of Fig. 3 with aperture aperture shifted in the diagonal direction B;

Fig. 6

Diagram representation of the focus size as a function of the photon flux for different traversing positions of the aperture window of Fig. 3 ;

Fig. 7

Diagram representation of the photon flux as a function of the beam divergence for different traversing positions of the aperture window of Fig. 3 ;

Fig. 8

Diagram representation of the photon flux density as a function of the photon flux for different traversing positions of the aperture window of Fig. 3 ;

Fig. 9

a schematic representation of a fully assembled aperture mechanism of an X-ray analysis according to the invention, in front view;

Fig. 10

a schematic representation of the diaphragm mechanism of Fig. 9 in oblique rear view;

Fig. 11

a schematic representation of the diaphragm mechanism of Fig. 9 , but without housing and adjusting screws;

Fig. 12

a schematic representation of the diaphragm mechanism of Fig. 9 , but without housing, but with adjusting screws;

Fig. 13

a schematic representation of a replaceable aperture-window element in a holder (diaphragm retainer) for the invention, in a plan view;

Fig. 14

the holder of Fig. 13 with the aperture window element removed, in a schematic oblique view;

Fig. 15a, 15b

schematic plan views of a shutter mechanism with adjustable size of the aperture opening for the invention, with two different, set window sizes;

Fig. 16

Assembly comprising a diaphragm mechanism in a diaphragm housing and an X-ray optics in one with the Blender housing assembled optical housing, for the invention, in a schematic oblique view;

Fig. 17a-17b

experimentally determined diffraction pattern of a small thaumatin crystal, with a spot size spot size of 0.25 mm ( Fig. 17a ) and with a beam with inventively reduced focus size at the sample location of 0.12 mm ( Fig. 17b );

Fig. 18a

a schematic representation of an X-ray analysis according to the invention;

Fig. 18b

a schematic cross-sectional view to Fig. 18a perpendicular to the beam propagation direction at the location of the aperture window;

Fig. 19a-19c

a schematic representation of different traversing positions of an aperture window relative to an x-ray beam, to illustrate the traversing paths of the aperture window according to the invention.

The invention relates to an X-ray analysis instrument, in particular an X-ray diffractometer, having an X-ray source, an X-ray optics, in particular a multi-layer X-ray mirror, and a variable diaphragm mechanism.

Multilayer X-ray optics and their applications in X-ray diffractometry are known, for example, from US Pat DE 198 33 524 A1 for so-called Göbelspiegel, and from the US 6,041,099 known for Montelspiegel (also called Monteloptiken). In these multi-layer X-ray mirrors, engineered multi-layer systems are used to generate X-rays Monochromatize, parallelize or focus applications in X-ray analysis. To provide a parallel beam, the mirror is parabolic, elliptical in shape to provide a focused beam. The multilayers must vary along the mirror in their "d-spacing" to satisfy the Bragg relationship for a single wavelength (eg, Cu-K alpha radiation) at each position of the mirror. The mathematical course of this layer thickness variation is known from earlier work (Laterally d-spacing graded multilayers, see eg M. Schuster et al., Proc. SPIE 3767, 1999, pp. 183-198 ).

Fig. 1 shows by way of example the essential geometric parameters of a focusing (elliptical) Göbelspiegels. Fig.1 shows a Göbelspiegel with the length L, the distance f1 to the source SC, and the distance f2 to the image focus IM and with the semi-axes a and b. α is the light collection angle and β is the convergence (or divergence) of the useful beam. The field of application of the mirrors described in this invention is X-ray diffractometry, with typical photon energies> 5000 eV. Under these conditions, the Bragg angles θ for typical Göbelspiegel in the range of less degrees, so that b «a applies. Therefore, f1 'is approximately equal to f1, and f2' is approximately equal to f2. The ratio f2 / f1 is called the magnification ratio of the optics.

Monteloptiken consist essentially of two Göbelspiegeln, which are mounted vertically to each other. While Göbel mirrors only parallelize or focus the X-ray in one dimension, Montel mirrors effect parallelization or focusing in two dimensions.

A disadvantage of these X-ray mirrors is that the beam properties on the output side of the mirrors are determined by the design of the optics. In the production of, for example, a focusing Göbelspiegels therefore physical variables such as the Ausgangsververgenz, the focal lengths between the source and image focus, the magnification and thus the size of the X-ray image focus before manufacturing. The quantities f1, f2, a, b, θ, L must be determined before production and can not be subsequently varied. A change to the requirements makes the costly and costly production of a new mirror type necessary. This makes the use inflexible for different sample requirements. Other sample requirements must be performed under suboptimal conditions, or require the change of optics, which is expensive and requires significant modification and costly adjustment of the system. A subsequent bending of the mirror to another form is out of the question, since in this case, the coating would have to be changed to fulfill the Bragg condition, which is subsequently no longer possible in the rule.

An essential ray property is the convergence β, since the resolution of the diffractometer decreases with increasing β: The separation of closely adjacent diffraction reflections of the sample requires a not too large β. If the sample requires a higher resolution, the mirror must be changed.

To adapt to changing measurement requirements, therefore, changing apertures (see DE 10 2004 052 350 A1 ) or an adjustable convergence diaphragm (see US 7,245,699 B2 ) proposed. DE 10 2004 052 350 A1 essentially describes a Nipkow disk or alternatively movable belts. Manufacturing these components with the required quality is difficult and their physical dimensions are quite large. An integration in the protection of optics usually evacuated or flushable with inert gas shielded beam path does not seem possible. In US 7,245,699 B2 the aperture always consists of a fixed and a movable part. The moving part blocks in the design of the US 7,245,699 B2 always only the source distant part of the reflected by the optics Radiation; this proportion is loud US 7,245,699 B2 less efficient than the near-source fraction.

However, in these prior art divergence limiting devices, beam conditioning capabilities are severely limited. In US 7,245,699 B2 the aperture consists of a rigid and a movable component. This can hide in particular only the source distant part of the radiation. At the exchangeable apertures DE 10 2004 052 350 the beam divergence is only stepped, but not continuously adjustable.

The aim of the present invention is to broaden the uses of X-ray optics by using an improved, very compact shutter mechanism and thus to improve the data quality of X-ray diffractometers in general.

The present invention proposes an X-ray analysis instrument, in particular an X-ray diffractometer, having an X-ray optics and a diaphragm mechanism consisting of one or more apertures which can be moved continuously in at least one direction, and preferably in two independent directions, perpendicular to the optical axis , And whose travel paths are at least twice as large as the X-ray beam emerging from the X-ray optics, so that any conceivable proportion of the X-ray beam emerging from the X-ray optics can be selected to illuminate the sample. Preferably, at least one fully open position should be achievable with the aperture mechanism. The diaphragm mechanism is preferably mounted on the output side of the X-ray optics.

The construction according to the invention is easy to operate over the prior art, of compact design and therefore cost can be produced, but allows a significant flexibility in the applications of X-ray optics and extremely simple and reproducible handling. It can even in existing, evacuatable optics housing, eg accordingly DE 10 2006 015933 B3 to be fully integrated. This will be explained in more detail below.

In the context of the present invention, a ray tracing program has been developed, which has been optimized for X-ray optics. Comparisons with experiments showed that this ray tracing program makes excellent, accurate predictions. In such ray tracing calculations, it has been found by the inventors that the beam profile on the output side of typical X-ray mirrors is often not homogeneous with respect to the intensity. Fig. 2 shows the ray tracing specific intensity profile of a 150 mm long multi-layer Montelspiegels. High intensity areas are dark, and areas of low intensity are bright. Out Fig. 2 It can be seen that the square beam profile is not homogeneously filled with intensity, but in the upper left corner is particularly dark (and thus rich in intensity). The intense beam area in the upper left corner of Fig. 2 was reflected twice each from a near-source portion of the Montelspiegels, and the lower-intensity beam area bottom right was reflected twice each of a source distant portion of the Montelspiegels. The cross section of the X-ray beam can be divided by the two dashed lines center lines M1 and M2 in each case in terms of area in a near-source and a source distant half with respect to each of the two reflections. From the quadrant on the top left, a source (with respect to both reflections) near the source of the X-ray beam can be selected, and from the quadrant at the bottom right one can select a source (with respect to both reflections). It should be noted that beam portions of the quadrants were reflected once near the source and once away from the source at the top right and bottom left. The graininess in Fig. 2 comes through the fact that the number of rays in the ray tracing program is finite.

On the basis of Fig. 2 At first glance, it may appear advantageous to have this especially dark portion in the upper left corner of the beam as well as in Fig. 4 used to illuminate the sample and to block out the remainder of the beam in the event that, for example, to reduce the divergence, a portion of the beam should be hidden. This corresponds to the procedure according to the prior art according to the US 7,245,699 B2 , The upper left corner apparently contains the after the US 7,245,699 B2 particularly efficient share. However, with ray tracing calculations and subsequent experimental investigations, the inventors have observed other unexpected effects, including the use of other parts than after US 7,245,699 B2 suggested or even after US 7,245,699 B2 possible, for example, the lower right part of the beam as in Fig. 5 sketched, of interest. In order to be able to bring the diaphragm (with regard to the at least one travel direction) into a completely closed position, the travel path of the diaphragm must be at least twice as large as the X-ray beam emerging from the X-ray optics.

In the following figures, the ray tracing calculations used a square aperture (aperture window 2) as in the FIGS. 3 to 5 sketched stepwise in either direction A or direction B, and then the beam properties were determined; the particular beam characteristics are in the FIGS. 6 to 8 shown. It should be noted that the directions A and B are equal to each other, and thus in the context of the invention, the direction pair A / B together only one traversing direction (traversing) of the aperture window 2 across the X-ray beam corresponds. Travel A corresponds in its effect according to the prior art US 7,245,699 B2 ; Travel path B is in the training after the US 7,245,699 B2 not possible or not provided, since here the supposedly less efficient beam component is. In Fig. 6 At 100%, the iris is fully opened along the x-axis. At the considered Example optics is the beam size in focus with fully open aperture about 0.2 mm. In the process of the diaphragm, it now appears that the beam becomes larger in the direction A in the method, and smaller in the method in the direction B. It is thus possible to vary the beam size and to adjust the sample size by choosing the direction of travel. This is very interesting for applications in single-crystal diffractometry for the structure determination of proteins and small organic molecules, where the samples often have a size in the range 0.1-0.3 mm. By the appropriate choice of the direction of travel of the diaphragm, one can set the best beam size, in which only the sample is illuminated. If the sample is smaller than 0.2 mm, then rays which do not hit the sample and which only lead to air scattering and thus generate a raised background in the diffraction measurement can be avoided. If the sample is greater than 0.2 mm, the beam can be increased by travel direction A, so that the sample is homogeneously illuminated, which is also advantageous for the measurement.

Fig. 7 shows that the direction of travel A is advantageous if the divergence is to be reduced, while the flow (photons / sec) should remain as high as possible.

Fig. 8 shows that the direction of travel B is advantageous if the flux density (photons / sec / mm ² ) should remain as high as possible.

These results show that different movement directions of the diaphragm alter the beam properties in different ways, and thus allow increased flexibility in the optimization of the beam properties with changing measurement requirements.

The FIGS. 6 to 8 can be used simultaneously as calibration curves when moving the aperture. All three curves intentionally contain the flow as the x or y axis, but not the travel of the orifice. The exact position of the X-ray in space may not be known exactly, and may change as a result of readjusting the optics or other circumstances. However, the flow on the output side of the diaphragm can be measured very easily, eg with a photodiode. So if you move the aperture, for example, in direction A, until the river is halved, so you can with the FIGS. 6 to 8 Immediately read the resulting beam size, divergence, and flux density. Conversely, to set a particular divergence, one can see how far one has to reduce the flow.

In addition to the traversing directions A and B shown diagonally through the square beam, of course, other beam cross sections, traversing directions (or travel direction pairs) and positionings of the diaphragm are possible.

A diaphragm mechanism BM constructed on the basis of the calculations (see Figures 9 and 10 ) for an inventive X-ray analysis instrument is arranged in a diaphragm housing 1 with optional loading window 7 and optional vacuum connection 4, wherein the diaphragm mechanism BM is equipped with a diaphragm (ie an aperture window 2 with aperture 3) and an adjustment mechanism with two actuators (here Micrometer screw 5 and fine thread bolt 6). In the FIGS. 9 to 14 the optics is rotated by 45 degrees, so that the square beam profile and thus also the square aperture 3 are on the top. Under these conditions, the diagonal movements of the FIGS. 3 to 5 to horizontal or vertical movements. Fig. 11 shows the central adjustment mechanism with diaphragm holder (holder) 11, not yet mounted in the housing. The aperture can be moved by two adjustments perpendicular to the beam direction in the X direction and in the Y direction. It is in the embodiment shown in the X direction via a micrometer screw 5 and in the Y direction by a fine thread bolt 6 adjustable, see. Fig. 12 , The aperture is mounted in a mounted on two axles 12 holder 11, which with two springs 13 against the micrometer screw 5 is pressed. Thus, an automatic reset of the aperture (or the aperture window 2) is ensured in this direction. The suspension of the adjustment mechanism, cf. Fig. 11 , Via two guide pins 14 and rotatably mounted in the aperture housing fine thread bolt 6; Thus, an entire frame 15 of the adjusting mechanism can be moved, cf. Fig. 12 ,

The movement of the aperture in the X and Y direction could also be done by means of other adjustment mechanisms, such as two micrometer screws, two simple screws, slots with screws, etc. A version with only a micrometer and a fine-threaded bolt is advantageous if the aperture only should be aligned once in height on a standing on the point square beam, while the adjustment to hide unwanted beam portions should be mostly horizontal.

To ensure an optimal aperture size and shape, the aperture can be made interchangeable, see. FIGS. 13 and 14 , In this case, an aperture window element 16, in which the aperture opening is formed, is held exchangeably in a holder 11. In FIG. 14 a removed aperture window element 16 is shown in front of the associated holder 11.

In the context of the present invention apertures with holes (aperture openings 3) of different shapes such as rectangles, diamonds, squares or circles can be used. A preferred design uses a standing on the top square. Another type is in the FIGS. 15a and 15b shown rectangle panel, in which the aspect ratios and the size can be adjusted, in particular with two L-shaped Aperturteilstücken 18 a, 18 b. A variable iris diaphragm can also be realized in this way.

The diaphragm housing 1 can, for example, in front of or behind an optical housing 17, for example DE 10 2006 015933 B3 be mounted, cf. Fig. 16 which can be evacuated via the vacuum connection 4 located in the cover housing 1. Thus, the diaphragm can be operated in vacuum or purged with inert gas, which prevents intensity losses of the beam and protects the optics from corrosion. The device is very compact. The beam then leaves the housing 1 through a beryllium window 7 located in the diaphragm housing 1.

The operating direction of the micrometer screw 5 can be changed by installing the adjusting mechanism in a different orientation and mounting the micrometer screw 5 on the opposite side. This facilitates the practical use in left- and right-sided system solutions. In order to continue to operate the housing 1 under vacuum, the hole not used by the micrometer screw is provided with a blanking plug 8.

Example of use:

A crystal of a defined size and with known lattice constants was mounted at a fixed distance from the source and the detector on an X-ray diffractometer (Smart Apex-11, Bruker AXS). The crystal had a long cell axis, which showed a tendency to reflections at the selected detector spacing. The crystal was oriented so that the closely adjacent reflections of the long cell axis were clearly visible on the detector.

As reference measurement several scans were performed with fully opened aperture and evaluated. The total flux of the open aperture source was measured with a photodiode and recorded. Now the scans were repeated on the same crystal with the iris set on halved flow and evaluated in an identical manner. The aperture was first faded out in the direction of travel A until it was halved (setting 1). The evaluation of the measured scans showed that the mean normalized diffracted intensity decreased to 33%. The signal-to-background ratio decreased to almost 60%. Now, with the aperture in direction of travel B, it was hidden except for halving (setting 2). Evaluation of the scans showed that the mean normalized diffracted intensity at setting 2 decreased to 45% and the signal to background ratio decreased to 74%. So setting 2 gave better data than setting 1.

By the method of the aperture on positions with reduced flow, the reflex separation was further improved advantageous. It could be detected more reflexes in the evaluation than with fully open aperture, as Table 1 can be seen. This finding was qualitatively consistent with the predictions of ray-tracing calculations, which did not include any specimen-specific properties such as crystal mosaic. Although the effect of better reflection separation is not dramatic in this application example, it becomes more pronounced with shorter detector spacings or with samples having even longer cell axes for the structure determination.

In summary, setting 2 (travel direction B) gave the better results, in contrast to the prior art according to the US 7,245,699 B2 , After a device of US 7,245,699 B2 this beam is not accessible. Apparently, the leads after the US 7,245,699 B2 Surprisingly, however, the beam proportion described as less efficient improves the signal-to-noise ratio. Table 1 Aperture Setting open (open) setting 1 setting 2 relative flux (relative photon flux) 1 12:49 12:48 #data (number of data points) 32051 32421 32411 resolution range 31.67 - 1.61 Å mean norm. I (mean normalized intensity) 418.6 135.9 187.2 mean l / sig (mean signal-to-background ratio) 22.6 14.2 16.8

The FIGS. 17a and 17b show two diffraction patterns on a small thaumatin crystal, once with an approximately 0.25 mm large beam ( Fig. 17a ), and once with a beam of about 0.12 mm ( Fig. 17b ). Although the photon flux in the case of the smaller beam was only a fraction of the total flux, the result was a much better diffraction pattern, ie much better data. This is essentially because the smaller beam essentially hits only the sample, while the larger beam additionally hits a portion of the sample holder and the surrounding air and excites scattering. This scattering leads to a raised background, which covers the diffraction reflexes.

Such a change in focus size has previously required a change in optics. With the shutter mechanism according to the invention, this is now a very simple and inexpensive way without changing the optics possible. After US 7,245,699 B2 only the path B is possible, which always leads to a beam magnification. This is how the experimental results of FIGS. 17a and 17b show, but unfavorable for small samples.

The Fig. 18a schematically shows an inventive Röntgenanalyseinstrument, here a Röntgendiffratometer 21. From an X-ray source 22, an X-ray beam 23 is emitted, which is from an X-ray optics 24, here a Göbel mirror, reflected and thereby focused. On the output side of the Göbelspiegels an aperture window 2 is arranged with an aperture 3 in the X-ray beam 23. The aperture window 2 is part of a diaphragm mechanism, and can be moved continuously in two independent directions x and y perpendicular to the propagation direction of the x-ray beam 23. Note that the y-direction is perpendicular to the plane of the drawing, and in the region of the aperture window 2, the z-direction is parallel to the propagation direction of the x-ray radiation. For stepless movement of the aperture window 2 means not shown in detail, such as a micrometer screw and a fine-threaded bolt, are formed in the aperture mechanism.

At the location (with respect to the z-direction) of the aperture 2 in the x direction has the X-ray beam 23 an extension RS _x and the aperture 2 has an extension AOE _x in the x-direction. According to the invention, RS _x <= AOE _x (in the exemplary embodiment shown, RS _{x is} slightly smaller than AOE _x ); The same applies to the corresponding quantities in the y-direction.

In the situation shown, the aperture window 2 is used to a first portion of the X-ray beam 23, namely a in Fig. 18 upper portion of the X-ray beam 23, through the aperture 3 to pass (see transmitted X-ray partial beam or portion 26), and a second (in Fig. 18a lower) portion of the X-ray beam 23. Through an upper part of the aperture 3, no X-radiation occurs. Of the transmitted partial beam 26 was at the x-ray optics 24 at a farther from the x-ray source 22, in the FIG. 18a The right-most region of the X-ray optics 24 is reflected, and is therefore referred to as a source distant portion of the X-ray beam 23. The shaded lower portion of the X-ray beam 23, however, was at a closer to the X-ray source 1 lying in the FIG. 18a Reflected left portion of the X-ray optics 24 and is therefore referred to as near source. It should be noted that in the illustrated case an adjustment of the aperture window 2 alone in the x-direction would be sufficient to select a source-distant or near-source portion of the x-ray beam 23. In a variant of the embodiment shown, therefore, the adjustment of the aperture window 2 in the y-direction can therefore be omitted, so that the aperture window 2 in only one direction, namely the x-direction, transversely to the propagation direction (here z-direction) of the x-ray beam 23 is movable ,

Only the partial beam 26 reaches the sample 27 in order to interact with it. Radiation diffracted by the sample 27 can be registered by means of a detector 28; the detector 28 is here movable on a circular arc around the sample 27.

In the Fig. 18b For example, the relationships in the cross-section 32 of the X-ray beam at the location (ie, the z-position) of the aperture window of FIG Fig. 18a illustrated in more detail. The substantially circular cross-section 32 is divided by the center line M into two parts (or halves) QNH, QFH with the same surface area. The in Fig. 18b The right-hand part QNH ("near-source half") was reflected closer to the source of the X-ray optics than the one in Fig. 18b left part QFH ("source far half"). With the aperture 3, a partial beam 26 is selected by overlapping with the cross section 32 of the X-ray beam. In order to select a source distant partial beam (portion) 26, while the aperture opening 3 is advanced to at most the center line M; in Fig. 18b the aperture 3 is not fully advanced to the center line M.

In the Figures 18a . 18b With the aid of an X-ray analysis instrument according to the invention, a source-remote portion of an X-ray beam is selected, as a result of which improved reflection separations and improved signal-to-background ratios can be achieved. With an X-ray analysis instrument according to the invention, however, any other beam components of the X-ray beam, for example a portion close to the source, can also be selected, depending on the requirements of the particular X-ray experiment. Furthermore, according to the invention, a source-distant beam component of the X-ray beam can also be selected with a conventional diaphragm, in particular a diaphragm with a smaller size than the beam cross-section or a mobility of less than twice the beam extension.

The FIGS. 19a to 19c illustrate the movability of an aperture window 2 according to the invention in a plane perpendicular to the propagation direction (in this case z-direction) of an x-ray beam, typically on the output side (behind) of a multi-layer x-ray optics. In the example shown, the aperture window 2 can be moved in two independent (and here also orthogonal) directions x and y via a travel path corresponding to twice the extent of the x-ray beam cross section in the respective direction; According to the invention, however, only one traversing direction (for example only the traversability in the x-direction shown) can be provided, or the traversing possibility in a second direction (approximately the y-direction) can be less than twice the extent of the x-ray beam in the second direction over a travel distance be reduced and serve only a fine adjustment of the aperture window.

Fig. 19a The aperture window 2 comprises a shading frame 31 and a (here) rectangular aperture 3. The aperture 3 has in the x-direction the extent AOE _x , and in the y-direction the extent AOEy. The X-ray beam has in the embodiment shown at the location of the aperture window 2 (unshaded) an oval cross section 32 with an extension RS _x in the x direction and RS _y in the y direction.

According to the present invention, the aperture opening 3 is at least as large as the cross section 32 of the X-ray beam, ie, the cross-section 32 of the X-ray beam is completely within the aperture opening 3 (in the fully open position). In the embodiment shown, RS _x = AOE _x and RS _y = AOE _y ; Within the scope of the invention, however, RS _x <AOE _x and / or RS _y <AOE _{y should also be} established.

Fig. 19b illustrates the mobility of the aperture window 2 in the x direction. The aperture window 2 can be displaced in the positive x direction at least to the extent that the aperture 3 no longer overlaps the cross section 32 of the x-ray beam. The same applies in the negative x-direction, cf. dashed aperture window 2 'with aperture 3'. For this purpose, the travel path VW _{x of} the aperture window 2 (indicated for the lower edge of the aperture 3) in the x-direction in the embodiment shown is at least twice as large as the extent _{x of} the x-ray in the x-direction. In the case of RS _x <AOE _x , a travel path VW _x > = RS _x + AOE _{x must be} established in order to be able to move the aperture window 2 out of the X-ray beam in both positive and negative x directions.

Fig. 19c illustrates the mobility of the aperture window 2 in the y-direction. The aperture window 2 can in turn be displaced in the positive y-direction, at least to the extent that the aperture 3 no longer overlaps the cross-section 32 of the x-ray beam. The same applies in the negative y-direction, cf. dashed aperture window 2 'with aperture 3'. For this purpose, the travel path VWy of the aperture window 2 (indicated for the left edge of the aperture 3) in the y direction in the embodiment shown is at least twice as large as the extent RS _{y of} the x-ray beam in the y direction. in the Case of RS _y <AOE _y is a travel VW _y > set = RS _y + AOE _y to move the aperture window 2 according to the invention in both the positive and negative y-direction from the X-ray beam.

Because the aperture 3 in the two independent spatial directions x and y can at least be moved out of the cross section 32 of the x-ray beam, a marginal portion of the cross section 32 can be selected for overlapping with the aperture 3 from each approaching direction and fed to a subsequent x-ray experiment , The remaining portion of the cross section 32 is then blocked by the shading frame 31. The area fraction of the selected subregion can also be selected steplessly in the two directions x and y, in particular in order to optimize photon flux, photon flux density and / or beam divergence in the subsequent x-ray analysis experiment due to the infinitely variable mobility of the aperture window 2. In addition, the entire X-ray beam in the fully opened traveling position of the aperture window 2 can be supplied to the following experiment. Optionally, the size of the aperture opening of the aperture window may also be adjustable, in particular reducible, and preferably infinitely variable, by the aperture mechanism, so that non-border portions of the cross section of the x-ray beam can also be selected (cf. Fig. 15a and Fig. 15b ).

The present invention allows the greatest possible freedom in the selection of a subarea of an X-ray cross-section for an X-ray analysis experiment.

Claims (15)

X-ray analysis instrument, in particular X-ray diffractometer (21), comprising an X-ray source (22; SC) which emits an X-ray beam (23), an X-ray optical system (24), in particular a multi-layer X-ray mirror, and a diaphragm mechanism (BM), wherein the diaphragm mechanism (BM) forms an aperture window (2, 2 ') with an aperture opening (3, 3') through which at least a part (26) of the x-ray beam (23) passes, characterized,
in that the diaphragm mechanism (BM) comprises means for continuously moving the aperture window (2, 2 ') in at least one direction (A / B, x, y) transversely to the x-ray beam (23),
that the aperture (3, 3 ') is at least as large as the cross-section (32) of the X-ray beam (23) at the location of the aperture (2, 2'),
and that the travel path (VW _x , VW _y ) of the aperture window (2, 2 ') accessible through the aperture mechanism (BM) in the at least one direction (A / B, x, y) is at least twice as large as the extent (RS _x , RS _y ) of the X-ray beam (23) at the location of the aperture window (2, 2 ') in this direction (A / B, x, y). An X-ray analysis instrument according to claim 1, characterized in that the diaphragm mechanism (BM) comprises means for continuously moving the aperture window (2, 2 ') in two independent directions (x, y) transverse to the X-ray beam (23),
and that the respective, through the aperture mechanism (BM) accessible Trajectory (VW _x , VW _y ) of the aperture window (2, 2 ') in each of the independent directions (x, y) is at least twice as large as the extent (RS _x , RS _y ) of the X-ray beam (23) at the location of the aperture window (2, 2 ') in the respective independent direction (x, y). X-ray analysis instrument according to claim 1 or 2, characterized
that the size of the aperture opening (3, 3 ') is not adjustable. X-ray analysis instrument according to claim 1 or 2, characterized in that by means of the diaphragm mechanism (BM), the size of the aperture (3, 3 ') is adjustable, wherein the aperture (3, 3') is adjustable to a size which is at least as large such as the cross section (32) of the X-ray beam (23) at the location of the aperture window (2, 2 '). X-ray analysis instrument according to claim 4, characterized in that the aperture mechanism (BM) for adjusting the size of the aperture (3, 3 ') has two mutually movable, L-shaped Aperturteilstücke (18a, 18b). X-ray analysis instrument according to one of the preceding claims, characterized in that the diaphragm mechanism (BM) is arranged on the output side of the X-ray optical system (24). X-ray analysis instrument according to one of the preceding claims, characterized in that the aperture window (2, 2 ') has a square aperture (3, 3') that the X-ray beam (23) at the location of the aperture diaphragm (2, 2 ') has an approximately square cross-section wherein the side edges of the square aperture (3, 3 ') and the square cross-section of the x-ray (23) are oriented parallel to each other, and that the at least one direction (A / B, x, y) into which the aperture window (2, 2 ') is movable is oriented along a diagonal of the square aperture (3, 3'). Röntgenanalyseinstrument according to any one of the preceding claims, characterized in that the X-ray optics (24) in a gas-tight optical housing (17) and the diaphragm mechanism (BM) in a gas-tight diaphragm housing (1) are arranged, wherein the two housings (1, 17) are evacuated or are flooded with a protective gas, or that the X-ray optics (24) and the diaphragm mechanism (BM) are arranged in a common, gas-tight housing, wherein the common housing is evacuated or flooded with a protective gas. X-ray analysis instrument according to one of the preceding claims, characterized in that the means for continuous movement of the aperture window (2, 2 ') comprise at least one micrometer screw (5) and / or at least one fine-threaded bolt (6). X-ray analysis instrument according to one of the preceding claims, characterized in that the diaphragm mechanism (BM) has a holder (11) for a replaceable aperture window element (16), and in that by the means for continuous movement of the aperture window (2, 2 ') the holder (11) is movable. Use of a diaphragm mechanism (BM) comprising an aperture window (2, 2 ') with an aperture (3, 3') for selecting a portion (26) of an X-ray beam (23),
wherein the X-ray beam (23) is emitted by an X-ray source (22; SC) and is imaged onto a sample (27) by X-ray optics (24), in particular a multi-layer X-ray mirror,
in particular wherein this use with a X-ray analysis instrument according to one of the preceding claims,
characterized,
in that for setting, in particular reducing, the focus size of the X-ray beam (23) at the location of the sample (27) by means of the aperture opening (3, 3 ') of the aperture window (2, 2'), a portion (26) which is remote from the X-ray optics (24). of the X-ray beam (23) is selected. Use according to claim 11, characterized in that the focus size of the X-ray beam (23) at the location of the sample (27) is adjusted to the size of the sample (27). Use according to claim 11 or 12, characterized in that the selected, remote source portion (26) of the X-ray beam (23) has a below average compared to the rest of the X-ray beam (23) average photon flux density. Use according to one of claims 11 to 13, characterized in that the aperture window (2, 2 ') is positioned so that no X-radiation (23) through part of the aperture (3, 3') of the aperture window (2, 2 '). occurs. Use according to one of claims 11 to 14, characterized in that the aperture window (2, 2 ') in the X-ray beam (23) between the X-ray optics (24) and the sample (27) is arranged.

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