Sample examination device using X-ray ultra-small angle scattering

Abstract

Apparatus for examining a liquid or powdered sample (140) by means of ultrasmall angle X-ray scattering, comprising: a beam shaping device (120) comprising an elliptical mirror (120), a monochromator (130), an analyzer (150), and a detector (160) for X-ray radiation, wherein the monochromator (130) is arranged between the beam shaping device (120) and the analyzer (150) and wherein the beam shaping device (120) is configured to focus an X-ray beam (115) in front of the monochromator (130); wherein the liquid or powdered sample (140) is arranged between the monochromator (130) and the analyzer (150), wherein a focus of the elliptical mirror (120) is directed towards the monochromator (130).

Description

[0001] The present invention relates to a device for examining a sample using ultra-small angle X-ray scattering, also known as "Ultra Small Angle X-Ray Scattering", USAXS.

[0002] To examine a material sample, it can be illuminated with X-rays. To draw conclusions about the sample's structure, the diffracted or scattered X-rays, particularly their angular distribution, can be analyzed. By analyzing the scattering of the X-rays and measuring the scattered radiation, inferences about the sample's structure can be made.

[0003] One such common structural analysis technique is small-angle X-ray scattering (SAXS), which consists of an X-ray source, a beam shaping device, the sample under investigation, and a detector. The beam shaping device includes collimation and monochromatization. With standard laboratory equipment, particles, clusters, or molecules up to 100 nm in diameter can typically be analyzed; with very good instruments, this can be achieved up to 200 nm.

[0004] Since SAXS measurements are naturally performed very close to the primary beam, as scattering is investigated at small scattering angles, this technique benefits from the brilliance of X-rays supplied by particle accelerators, the so-called synchrotrons.

[0005] However, if one wants to examine samples containing objects with larger diameters, i.e., larger than the previously mentioned 100-200 nm, this places higher demands on the apparatus, as smaller angles then need to be resolved. This is due to the Bragg equation, which shows that an increasing structure size results in smaller scattering angles. In other words, it is necessary in this case to use an ultrasmall angle scattering (USS) apparatus. Using a monochromator and an analyzer, the momentum magnitude resulting from the scattering process is measured as a function of the rotation angle of the analyzer crystal and an "OD" detector, and not, as is usual with SAXS, via an intensity change as a function of the angle at a 2D detector. A 2D detector is a detector that provides two-dimensional information about the impact or detection location of a particle; a 0D detector, on the other hand, provides no spatial information.Therefore, a single large pixel is sufficient to detect the X-rays that pass through the analyzer.

[0006] Typically, a collimation system is used to produce a parallel beam. A channel-cut, for example made of germanium, can be used as both the monochromator and the analyzer. An X-ray-sensitive detector, such as a proportional counter or a scintillation counter, can be used as the detector. The problem with this setup is that, due to the significant intensity reduction caused by collimation, measurements can only be performed at a very powerful X-ray source, such as a synchrotron. In a laboratory setting, however, the collimation system would block almost all X-ray quanta, and this, combined with the low power of typical laboratory X-ray tubes, makes the examination virtually impossible.

[0007] The publication EP 1 876 440 B1 describes how, in addition to the aperture system, a parabolic multilayer mirror can be used to collect and collimate the radiation from the X-ray source. However, the achievable beam yield is still not optimal. Furthermore, a parabolic multilayer mirror is only suitable for setups used to measure solid samples or powders that are sandwiched or stabilized between two films. When examining liquid samples or powders in capillaries with very thin walls, the X-ray beam must be collimated after the parabolic multilayer mirror using apertures. Typical beam diameters after the parabolic multilayer mirror are approximately 2 mm, while a capillary typically has a diameter of 0.5 to 1 mm.Therefore, if a beam of 2 mm has to be "cut down" to 0.5 mm, 15 / 16 of the intensity is lost, leaving only a small fraction of approximately 6% of the original intensity.

[0008] The publication EP 3 124 961 A1 discloses a microbeam generation unit for a small-angle X-ray scattering device, which generates X-rays with a microspot size with which a sample is irradiated in order to detect the diffracted X-rays with a one-dimensional or two-dimensional detector.

[0009] The publication by Sztucki et al. [2] concerns the optimization of a Bonse-Hart instrument for small-angle scattering by suppressing surface-induced parasitic scattering radiation.

[0010] The publications EP 3 141 889 A1, US 2001 / 0 028 699 A1, EP 1 469 304 A2, US 2007 / 0 009 091 A1, as well as the publications by Sun et al. (2013) [3] and Seller et al. (2000) [4] also concern the technical field of X-ray analysis.

[0011] The present invention is based on the objective of enabling small-angle X-ray scattering on liquid or powdered samples, even using a conventional laboratory X-ray device.

[0012] In a first embodiment, a device for examining a sample by means of small-angle X-ray scattering comprises a beam shaping device comprising an elliptical mirror or a polycapillary, a monochromator, an analyzer, and an X-ray detector, wherein the monochromator is arranged between the beam shaping device and the analyzer, and wherein the beam shaping device is configured to focus an X-ray beam in front of the monochromator.

[0013] According to another embodiment, the beam shaping device can include a focusing element that focuses the X-ray beam in such a way that a focus of the X-ray beam lies in the area between the monochromator and the detector, or close behind the detector.

[0014] According to another embodiment, the beam shaping device can comprise an elliptical multilayer mirror.

[0015] According to another embodiment, the beam shaping device can comprise a focusing or parallelizing polycapillary.

[0016] According to another embodiment, the device can be configured to include a sample.

[0017] According to another embodiment, the sample can be arranged between the monochromator and the analyzer.

[0018] According to another embodiment, the monochromator can isolate a first wavelength range from the X-ray beam.

[0019] According to another embodiment, the monochromator can comprise a channel-cut monochromator.

[0020] According to another embodiment, the analyzer can be arranged between the sample and the detector and can be rotatable, allowing the radiation scattered by the sample to pass through only at a certain angle of rotation.

[0021] According to another embodiment, the analyzer can include a channel-cut analyzer.

[0022] According to another embodiment, the channel-cut monochromator and / or the channel-cut analyzer can consist of a single-crystal material that can reflect the characteristic radiation of the X-ray source.

[0023] According to another embodiment, the device can include an X-ray source configured to provide the X-ray beam.

[0024] According to another embodiment, the detector can include a hybrid pixel detector.

[0025] In a further embodiment, a small-angle X-ray scattering examination method for a sample is specified, comprising: shaping an X-ray beam with an elliptical mirror or a polycapillary as a beam shaping device, monochromatizing the shaped X-ray beam, analyzing X-ray radiation generated by scattering the X-ray beam at a sample; and detecting the X-ray radiation, wherein the monochromatizing takes place between the beam shaping device and the detector, and the beam shaping device focuses the X-ray beam in front of the monochromator. Fig. Figure 1a shows the schematic structure of a device according to an embodiment of the present invention; Fig. 1b shows a different schematic setup of the device according to a further embodiment; Fig. Figure 2 shows a further schematic setup of the device with alternative beam shaping according to a comparative example; and Fig. Figure 3 shows a schematic flowchart of a procedure for examining a sample using small-angle X-ray scattering.

[0026] As previously described, a parabolic multilayer mirror can be used to align the X-ray beam. In contrast, according to one embodiment of the present invention, an elliptical mirror is used, which can focus the X-ray beam, for example, to 0.5 mm at the level of the sample. Thus, none of the original intensity would need to be attenuated. Even if an aperture were used in this case, the X-ray beam would only need to be reduced from, for example, 0.5 mm to 0.4 mm, which would result in only a relatively small loss of intensity.

[0027] Fig. 1a, Fig. 1b and Fig. Figure 2 shows two different variants of the device, in which different means are used as beam-shaping elements. Fig. 1a and Fig. 1b an elliptical mirror is used, Fig. 2 a polycapillary. Fig. Figure 1b shows the case in which the focus of the elliptical mirror is directed towards the monochromator. Fig. Figure 1a shows the case where the focus is at the detector.

[0028] In Fig. 1a and Fig. Figure 1b shows an X-ray source 110. An X-ray source 110 can, for example, comprise a conventional electron gun and a transmission or reflection target. The interaction of the electron beam in the target material produces X-ray radiation 115, which includes characteristic radiation as well as bremsstrahlung.

[0029] The X-ray radiation 115 emitted from the X-ray source 110 strikes a beam-shaping element, the elliptical mirror 120. Such an elliptical mirror is characterized by the special shape of its reflecting surface, which in this case corresponds to a section of an ellipsoid, and exhibits specific reflection properties. The mirrors used can be so-called multilayer mirrors, which are characterized by high reflectivity in certain wavelength ranges. These mirrors have a multilayered structure of the reflecting surface.

[0030] This mirror 120 focuses the X-ray radiation 115, which then strikes the monochromator 130. The monochromator 130 ensures that the X-ray radiation 115 essentially has only a narrow wavelength band, for example, with a width of a few tens of eV. A so-called channel-cut monochromator can be used as the monochromator, for example.

[0031] The monochromatic X-ray radiation 115 passes through the sample 140. As mentioned above, the sample 140 can be a solid sample, but liquid or powdered samples can also be examined; these must be enclosed in suitable sample holders if necessary. When the sample 140 is passed through, the X-ray radiation 115 is scattered.

[0032] After the X-ray radiation 115 has passed through the sample 140 and been scattered there, the scattered X-ray radiation enters the analyzer 150. The analyzer 150 operates similarly to the previously described monochromator 130 and selects the X-ray radiation 155 scattered by the sample 140 according to its direction. To select the X-ray radiation 155 according to direction, the analyzer 150 is rotatable. A so-called channel-cut analyzer, for example, can be used as the analyzer.

[0033] The detector 160 is arranged in the beam path after the analyzer 150. This detector is designed, for example, for the wavelength range selected by the monochromator. Scintillation counters or proportional counters can be used. However, the use of hybrid pixel detectors can be advantageous. In such a hybrid pixel detector, readout electronics with a threshold are located behind each pixel. If the deposited charge is higher than the threshold, the detector counts a photon. In some embodiments, a semiconductor detector can be segmented, i.e., have pixels. Such a detector generally exhibits no electronic noise and thus provides a better signal-to-noise ratio [1].

[0034] In Fig. Figure 1a shows an optional aperture 125, which cuts the X-ray beam between the elliptical mirror 120 and the monochromator 130. This can be used, but is usually obsolete due to the use of the elliptical mirror 120.

[0035] Fig. 1a differs from Fig. 1b mainly because the focal point 165, which the mirror 120 creates, is located in different places, in the example of the Fig. 1a the focus 165 lies in the area of ​​detector 160, in the example of the Fig. 1b the focus 165 lies in the area of ​​the monochromator 130, in this case more precisely in the entrance area of ​​the monochromator 130.

[0036] In a Fig. In the further embodiment shown in Figure 2, a polycapillary can be used instead of the elliptical mirror. This simplifies the overall setup. When using a multilayer mirror, whether elliptical or parabolic, adjusting the mirror is relatively complicated because an angle of approximately 6 degrees must be achieved between the X-ray source 110 and the emitted beam of the mirror. Therefore, not only must the exact position of the mirror be found in all three spatial directions, but also the correct tilt angle, which can require a very time-consuming adjustment process.

[0037] If, however, a polycapillary is used, it only needs to be placed vertically at the correct distance from the outlet of the X-ray source. This allows for a straight-line setup, eliminating the need for an angle between the X-ray source and the mirror.

[0038] In Fig. Figure 2 shows an example of an embodiment in which such a polycapillary is used. Analogous to the embodiments of Fig. 1a+b is in Fig. Figure 2 shows an X-ray source 210. As explained previously, the X-ray source 210 can, for example, comprise a conventional electron gun and a transmission or reflection target. X-ray radiation 215 is generated in the X-ray source 210.

[0039] The generated X-ray radiation 215 strikes a beam-shaping element, the aforementioned polycapillary 220. Such a polycapillary 220 is able to focus or parallelize the incoming X-ray radiation 215, analogous to mirrors. For solid samples, such as platelets or powders, a parallelizing polycapillary could be used, for example; for liquid samples, which may be enclosed in a capillary, a focusing polycapillary could be used to achieve high intensities within the sample volume.

[0040] The X-ray radiation 215 passing through the polycapillary 220 next encounters the monochromator 230, which ensures that the X-ray radiation 215 essentially has only a single wavelength. The channel-cut monochromators described above can be used as monochromators.

[0041] The monochromatic X-ray radiation 215 illuminates the sample 240, which can again be a solid sample or a liquid or powdered sample.

[0042] After the X-ray radiation 215 has been scattered by the sample 240, the scattered X-ray radiation enters the analyzer 250, which can select the X-ray radiation 215 scattered by the sample 240 according to its direction.

[0043] The detector 260 is arranged in the beam path after the analyzer 250. This detector can be, for example, a scintillation counter, a proportional counter, or a semiconductor detector, as described above.

[0044] As mentioned, the elements used for beam shaping can focus the beam, that is, reduce its divergence. This leads, for example, to a parallel beam in some cases when a parallelizing element such as a polycapillary is used, and to a focused beam in other cases when a focusing element such as a multilayer mirror is used.

[0045] When the beam is focused, it is possible to place the focus at different positions along the beam path. In some cases, it may be advantageous to place the focus near the sample, while in others it is more beneficial to place it near the detector. The term "near the detector" can refer to whether the focus is located in front of or behind the detector, or even within the detector itself. If the focus is located in front of or behind the detector, this can be immediately in front of or behind it, for example, in the range of 0 to 5 millimeters in front of / behind it, or it can be close to the detector, for example, in the range of 0 to 5, 10, or 25 centimeters in front of or behind it. The area in front of the detector refers to the side of the detector facing the analyzer, and the area behind the detector refers to the side of the detector facing away from the analyzer.

[0046] The described embodiments have in common that they include both a monochromator and an analyzer. These elements serve to selectively transmit incident radiation, such as the X-rays used here, according to wavelength and direction. This means that radiation deviating from the desired wavelength and direction is filtered out. The monochromator can be configured to select the incident X-rays according to wavelength, while the analyzer can be configured to transmit the radiation scattered by the sample only at a specific angle, i.e., to select it according to direction. For example, in the described case of small-angle X-ray scattering, this allows for the filtering out of interfering background radiation, because since the process under consideration is elastic, no wavelength change occurs, and all wavelengths except the initial one can be ignored.

[0047] Channel-cut monochromators, for example, can be used as monochromators and / or analyzers. These can consist of a single-crystal material into which a channel has been sawn or milled. Within this channel, fine wavelength selection takes place through multiple reflections. Germanium, for example, can be used as the single-crystal material, but silicon is also possible and can be considered, among other reasons, for cost reasons.

[0048] Fig.Figure 3 shows a schematic flowchart of a procedure for examining a sample using small-angle X-ray scattering. In a first step 310, an X-ray beam is shaped using an elliptical mirror or a polycapillary as a beam shaping device. In a second step 320, the shaped X-ray beam is monochromatized. In a third step 330, the X-ray radiation generated by scattering the monochromatized X-ray beam from a sample is analyzed, and in a fourth step 340, this X-ray radiation is detected. The monochromatization 320 takes place between a beam shaping device and a detector. The X-ray beam is focused by the beam shaping device in front of a monochromator.

[0049] Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding process, so that a block or component of a device is also to be understood as a corresponding process step or as a feature of a process step. Similarly, aspects described in connection with or as a process step also constitute a description of a corresponding block, detail, or feature of a corresponding device.

[0050] The embodiments described above merely illustrate the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other people skilled in the art. Therefore, it is intended that the invention be limited only by the scope of protection set forth in the following claims and not by the specific details presented herein by way of description and explanation of the embodiments. References: [1] Johnson et al., “Eiger: a single-photon counting x-ray detector,” Journal of Instrumentation, Vol. 9, May 2014 [2] Sztucki et al.: “Optimization of a Bonse-Hart instrument by suppressing surface parasitic scattering,” Journal of Synchrotron Radiation, Vol. 15, No. 4, 2008, pp. 341-349 [3] Sun et al.: „Performance of polycapillary X-ray optics for confocal energy-dispersive small-angle X-ray scattering“, Journal of Applied Crystallography, Vol. 46, 2013, S. 1880-1883 [4] Seller et al.: „Photon counting hybrid pixel detector for X-ray imaging“, Nuclear Instruments and Methods in Physics Research A, Vol. 455, 2000, S. 715-720

Claims

[1] Apparatus for examining a liquid or powdered sample (140) by means of ultrasmall angle X-ray scattering, comprising: a beam shaping device (120) comprising an elliptical mirror (120), a monochromator (130), an analyzer (150), and a detector (160) for X-ray radiation, wherein the monochromator (130) is arranged between the beam shaping device (120) and the analyzer (150) and wherein the beam shaping device (120) is configured to focus an X-ray beam (115) in front of the monochromator (130); wherein the liquid or powdered sample (140) is arranged between the monochromator (130) and the analyzer (150), wherein a focus of the elliptical mirror (120) is directed towards the monochromator (130). [2] Device according to claim 1, wherein the beam shaping device (120) comprises an elliptical multilayer mirror. [3] Device according to one of claims 1 to 2, wherein the monochromator (130) is configured to isolate a first wavelength range from the X-ray beam (115). [4] Device according to any one of claims 1 to 3, wherein the monochromator (130) comprises a channel-cut monochromator. [5] Device according to any one of claims 1 to 4, wherein the analyzer (150) is arranged between the sample (140) and the detector (160) and is rotatable and is configured to allow the radiation scattered by the sample (140) to pass through only at a certain angle of rotation. [6] Device according to claim 6, wherein the analyzer (150) comprises a channel-cut analyzer. [7] Device according to any one of claims 4 to 6, wherein the channel-cut monochromator and / or the channel-cut analyzer consist of a single-crystal material that can reflect the characteristic radiation of the X-ray source. [8] Device according to any one of claims 1 to 7, further comprising: an X-ray source (110) which is set up to provide the X-ray beam (115). [9] Device according to any one of claims 1 to 8, wherein the detector (160) comprises a hybrid pixel detector. [10] X-ray ultrasmall angle scattering analysis method for a liquid or powdered sample, comprising: Shapes (310) of an X-ray beam (115) with an elliptical mirror (120) beam shaping device (120), Monochromatizing (320) the shaped X-ray beam (115) by a monochromator (130), Analyzing (330) X-rays (155) by an analyzer (150) produced by scattering the monochromatic X-ray beam (115) on a liquid or powdered sample (140); and Detecting (340) the X-ray radiation (155); wherein the monochromatization (320) takes place between the beam shaping device (120) and a detector (160) and the X-ray beam (115) is focused by the beam shaping device (120) in front of the monochromator (130); wherein the liquid or powdered sample (140) is arranged between the monochromator (130) and the analyzer (150), wherein a focus of the elliptical mirror (120) is directed towards the monochromator (130).

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