Monochromator chamber and monochromator

Abstract

The invention relates to a monochromator chamber for a monochromator for x-ray radiation, and to a monochromator having a monochromator chamber according to the invention. According to the invention, the monochromator chamber is in the form of a cylinder or prism with a main axis and two side walls. The monochromator chamber comprises at least one incidence window for an incident x-ray and an exit window for an exiting x-ray. A course direction for an incident and exiting x-ray is predefined by the incidence and exit windows. According to the invention, the incidence and exit windows are arranged such that the course directions defined by them for x-rays in the monochromator chamber form an angle γ> 0° with the main axis of the monochromator chamber.

Description

[0001] Monochromator chamber and monochromator

[0002] Technical area

[0003] The present invention relates to a monochromator chamber and a monochromator with a monochromator chamber according to the invention, such as those used, for example, in X-ray diffraction.

[0004] State of the art

[0005] Monochromators of the type relating to the invention are known from the prior art and are described, for example, in Article 1 by F. Senf et al. (A plane-grating monochromator beamline for the PTB undulators at BESSY II; Journal of Synchrotron Radiation Vol. 5, 1998, pp. 780-782). They essentially consist of reflection optics for monochromatizing and focusing an X-ray beam incident on the optics, such as plane mirrors and plane gratings. After monochromatization and, if necessary, reflection, the X-ray beam exits the monochromator and is made available for further use.

[0006] Monochromatization here refers to a restriction of the spectral width A l around a specific wavelength A for which the diffraction conditions on the plane grating are met. The quality of the monochromatization depends, among other things, on the achievable spectral width of the diffracted X-ray beam. A specific wavelength A can be selected by adjusting the line density N (lines / mm) of the plane grating or the grating spacing in a crystal by setting a corresponding total deflection angle 29 on the mirror or crystal, and in the case of plane grating monochromators, additionally by changing the diffraction angle / ? of the incident beam. This causes this beam to be monochromatized for a diffraction order "m" in the further beam path.

[0007] A = (sin

[0008] By using a plane mirror, the light is offset in height in the further beam path. A large wavelength range λ requires large angular ranges for the total deflection angle 2θ and diffraction angle β. For the total deflection angle 2θ, long plane mirrors are used in plane grating monochromators according to DE 3045 931 A1. In the disclosed arrangement, an increase in the rotation range results in an increase in the space required in the monochromator chamber. For the linguistically correct classification of the terms in the prior art, it should be noted that a monochromator may or may not include a monochromator chamber, and that a monochromator chamber with a monochromator together can also be referred to simply as a monochromator.

[0009] The optics, i.e., the monochromators themselves, are housed for specific applications in an evacuable housing, the monochromator chamber, which is equipped with at least entrance and exit windows or slits for the incoming and outgoing X-rays. To change the monochromatization conditions, the optics are each equipped with drives that allow them to rotate about an axis, with these axes arranged perpendicular to the incident X-ray beam. To record the currently set angle of the drives, these can be equipped with angle decoders. The volume of the monochromator chambers determines the duration and pump power required to evacuate the chamber (evacuation capability).Evacuation of the monochromator chambers is particularly necessary at wavelengths where the absorption of X-rays in air is high, especially in the extreme ultraviolet (XUV) range. However, the volume of the monochromator chamber also determines the space available within the chamber for the arrangement of the monochromators and their drive units. In particular, the rotation of the axes of the monochromator optics, which can also occur eccentrically, creates space requirements, and the rotation is limited by the available space.

[0010] The monochromator chambers considered in connection with the invention are characterized by the fact that they are designed in the geometric shape of a cylinder, in particular a right cylinder, as a general case, and as a special case of this also as a prism, in particular a right prism, whereby the cylinder or prism is closed. The prismatic shape also includes, in particular, cuboids. For the purposes of the invention, the cylinder also includes those with an elliptical cross-section. A cylinder or a prism, whether oblique or straight, is always characterized by the cylinder axis or main axis of the prism. An ellipsoid and a cube are also possible as limiting shapes. The cylindrical shape, in particular, is further characterized by shape-related, manufacturing-technically advantageous properties, since there are only two edges. The cylindrical or prismatic chambers are closed off by side walls at the ends of the cylinder or prism.The side walls are arranged perpendicular to the main axes, resulting in straight bodies, which is advantageous for manufacturing. The side walls do not necessarily have to be flat. Outwardly curved designs are particularly advantageous for stabilization. Evacuable monochromator chambers (recipients) are advantageously designed in a cylindrical shape due to the external atmospheric pressure and the resulting large surface forces, and are equipped with end faces designed as dished ends for stabilization.

[0011] The monochromator chambers known in the prior art, with the monochromators arranged within them, are aligned with the incoming and outgoing X-rays in such a way that the beam path runs through the optics of the monochromators in the monochromator chambers such that both the incoming and outgoing X-ray beams run parallel to the main axes of the monochromator chambers. Accordingly, the entrance and exit windows in the chambers are located on the side walls, possibly slightly offset from each other in their position on the side walls. The entrance and exit windows each determine the directions of travel for the incoming and outgoing X-rays in the beam path of the monochromators.The parallel arrangement of the paths to the main axis of the monochromator chamber is advantageous in terms of manufacturing technology and facilitates the orientation of the optics of a monochromator in a monochromator chamber and the alignment and adjustment with respect to an incident X-ray beam. The monochromator chambers concerned by the invention are intended for the formation of monochromators which, in particular, have beam paths in which - apart from diffraction of the X-rays - there is only a slight offset between the incoming and outgoing X-ray beams, as is the case, for example, for planar grating monochromators or double-crystal monochromators, so that an imaginary connection between the inlet and outlet windows almost coincides with the beam path via the optics of the monochromators and, if necessary, even a line of sight exists between the windows.

[0012] Task

[0013] The object of the invention is to provide a monochromator chamber which is optimized both in terms of evacuability and in terms of space in the chamber and thus the rotation range for optics to be arranged in the chamber, and is advantageous in terms of manufacturing technology.

[0014] The object is solved by the subject matter of claims 1 and 4. Advantageous embodiments are the subject matter of the subclaims.

[0015] The monochromator chamber according to the invention is intended for accommodating a monochromator for X-rays. The monochromator chamber is in the shape of a cylinder or a prism and thus has a main axis, the cylinder axis or main axis in the prism. The monochromator chamber is supplemented and enclosed by two side walls, which can be either flat or rounded. Furthermore, the monochromator chamber comprises at least one incidence window and one exit window for an incoming X-ray beam and one exit window for an outgoing X-ray beam. The incidence window and the exit window determine the paths for the incoming and outgoing X-ray beams, which run congruently with the beam path of the monochromator optics to be arranged in the monochromator chamber.In accordance with the generic monochromators of the invention, the paths for the outgoing and incoming X-ray beams run in the same plane at a fixed angle to one another and also parallel. According to the invention, both paths now enclose a constant angle / with the main axis of the monochromator chamber, whereby both paths - that for the incoming and that for the outgoing X-ray beam - lie in the same plane with the main axis of the monochromator chamber. The angle y is greater than 0°. These geometric relationships result in the incidence window and the exit window being arranged on the side walls in opposite eccentric positions (to the cylinder or main axis) or even being arranged on the cylinder jacket or one of the prism surfaces or edges.An imaginary connecting line between the incidence and exit windows does not have to run through the center of gravity of the shape determined by the monochromator chamber, but is advantageously spaced from it, so that two compartments of different sizes are formed in the monochromator chamber, which are marked by the course of the imaginary connecting line, in which a monochromator is to be arranged in the chamber on this connecting line and the part of the chamber in which the monochromator is arranged forms a compartment.The monochromator chamber according to the invention is oriented according to the X-ray propagation directions when used with the optics of an X-ray monochromator such that the incoming and outgoing X-ray beams coincide with the propagation directions. This results in the main axis of the monochromator chamber, and thus also its geometric shape, being tilted - corresponding to the angle enclosed by the propagation directions and the main axis / relative to the orientation in which the main axis is oriented parallel to the propagation direction of the incoming X-ray beam or coincides with it. The X-ray radiation, for which a monochromator of the generic type is usually used for the invention, usually originates from a synchrotron and is thus horizontal, at least as viewed by the experimenter at the synchrotron.The proposed arrangement of the windows in the monochromator chamber thus results in a tilt of the chamber relative to the horizontal plane. The tilt direction is particularly oriented towards a monochromator to be arranged in the monochromator chamber and its intended orientation with respect to an incident X-ray beam.

[0016] Due to the inventive arrangement of the windows and the resulting predetermined directions of travel of the incoming and outgoing X-rays, the arrangement of the monochromator's optics in the monochromator chamber is shifted compared to the prior art in the inventive monochromator chamber toward the part of the chamber determined by the directions of travel. This shift and the tilting of the X-ray directions relative to the main axis of the monochromator chamber free up space in the other part of the monochromator chamber, which can be used for rotating (pivoting) the optics for monochromatization in the chamber. This increases the possible rotation range of the monochromator's axes and thus the range of applications (in terms of possible monochromatization with respect to energy / wavelength) of a monochromator in a monochromator chamber according to the invention.This increase in rotation range is achieved by the invention without enlarging the monochromator chamber or, if necessary, redesigning it, but simply by relocating the windows and rotating (tilting) the entire monochromator chamber compared to the conventional arrangement. However, the volume does not increase, thus ensuring that evacuation is not compromised, which is another advantage of the invention.

[0017] In one embodiment of the invention, the angle y enclosed by the directions of travel predetermined for X-rays in the monochromator chamber through the windows and the main axis of the chamber is y > 20°.

[0018] According to the invention, the angle y is furthermore in particular < 90° and in particular < 45°. The invention makes particular use of an extension of the monochromator chamber, which is designed to be prismatic or cylindrical and, in the limiting case, elliptical or cubic, along the main axis in order to arrange optics which also have a direction of particularly pronounced extension, such as certain plane mirrors, without increasing the volume of the monochromator chamber to increase the rotation range of the optics. In particular, plane mirrors are designed to completely capture an X-ray beam at small diffraction angles with a significant extension in one direction and are advantageously arranged in a monochromator chamber according to the invention as part of a monochromator to be arranged therein with an enlarged rotation range.The invention also works for monochromator chambers whose major axis is shorter than the other dimensions within the chamber, although the effect achieved is smaller in this case. The X-ray beam paths determined by the inventive arrangement of the windows in the monochromator chamber do not necessarily have to correspond to a spatial diagonal in the cylinder or prism.

[0019] In a third embodiment of the invention, the incident window is formed as a flange on the cylindrical or prism shell. Furthermore, a monochromator for X-rays is claimed, which comprises at least one monochromator chamber according to the invention, corresponding to the above description thereof, and a monochromator for X-rays. The beam path of the monochromator, with its incident and exit directions for X-rays, is congruent with the directions of travel for X-rays in the monochromator chamber, which are determined by the incident and exit windows of the monochromator chamber.

[0020] The monochromator according to the invention includes all the advantages provided by the monochromator chamber according to the invention and the associated arrangement of the optics, in particular the enlarged angular range for y with a simultaneous volume favorable for evacuation.

[0021] Example

[0022] The invention will be explained in more detail in an embodiment and with reference to two figures.

[0023] The figures show:

[0024] Fig. 1: Schematic representation of a monochromator with monochromator chamber according to the state of the art ( / = 0°)

[0025] Fig. 2: Schematic representation of a monochromator with monochromator chamber according to the invention (y — 20°)

[0026] Fig. 1 shows a monochromator 1 with a monochromator chamber 2, as is known from the prior art. The monochromator 1 comprises a monochromator chamber 2, an incidence window 3 and an exit window 4 for X-rays (not shown). The incidence window 3 and the exit window 4 determine the directions (— ) of incident and exit X-rays in the monochromator chamber 2, which directions congruent with a beam path (•••) of the monochromator (represented by the plane mirror 5a and the plane grating 5b), which is arranged in the monochromator chamber 2, with regard to its direction of incidence and exit. The monochromator chamber 2 is designed as a cylinder with curved (rounded) side walls 6a, 6b and has a main axis (the cylinder axis, — ).The principal axis (— ) coincides with both the direction of travel (— ) for incoming X-rays and the direction of incidence onto the monochromator in its beam path (— ). The direction of travel for outgoing X-rays, in turn, coincides with the direction of exit in the monochromator's beam path. In the figure, the lines for these directions cannot be distinguished in this area. The plane mirror is rotated eccentrically using a mechanism 7, according to DE 10 2022 130 836. Furthermore, the bearing 8 of the monochromator chamber is indicated, and the angles ß and 2θ, which determine the diffraction according to (1), are also drawn.

[0027] An embodiment of a monochromator 1' with a monochromator chamber 2' according to the invention is shown in Fig. 2. The monochromator 1' comprises a monochromator chamber 2' according to the invention with an incident window 3' and an exit window 4' for X-rays (not shown). The incident window 3', designed here as a flange, and the exit window 4' determine the directions of travel (— ) for X-rays in the monochromator chamber 2', which directions of travel congruent with a beam path (■••) of the monochromator (represented by the plane mirror 5a and the plane grating 5b), which is arranged in the monochromator chamber 2', with regard to its direction of incidence and exit.Due to the inventive arrangement of the windows 3', 4', the paths (— ) for X-rays in the monochromator chamber 2' are tilted relative to the main axis (the cylinder axis, — ) of the monochromator chamber 2' and enclose an angle / greater than zero, in the exemplary embodiment y- 20°, with the same. Due to the inventive arrangement, space is freed up in the part of the monochromator chamber 2' that does not contain the monochromator including the plane grating 5b, which is available for pivoting (rotating) the plane mirror 5a of the monochromator and as a result of which the rotation range for the plane mirror is significantly increased (20 + 2 / vs 20 ) compared to the arrangement according to the prior art, as shown in Fig. 1.The long plane mirror in the plane grating monochromator shown in the exemplary embodiment is suspended eccentrically from a pivot point according to DE 3045 931 A1, so that when the mirror rotates, the incident beam travels along the mirror surface and, at the same time, the grating is always centrally illuminated by the reflection of the mirror. Here, too, the plane mirror is rotated eccentrically using a mechanism 7 according to DE 10 2022 130 836. Furthermore, the bearing 8 of the monochromator chamber is also indicated in this figure. The angle y, by which the monochromator chamber is tilted relative to the main axis (— ), is marked in the figure. Also marked is the additional space (double arrow) in the monochromator chamber gained by the arrangement according to the invention. The monochromator chamber 2' in the exemplary embodiment corresponds in manufacture to the monochromator chamber 2 known from the prior art.The advantage of the inventive design of the monochromator chamber 2' and the resulting arrangement of the monochromator (5a, 5b) in the chamber 2' is evident from the space gained (double arrow arc), which in the example results in a larger rotation range for the plane mirror 5a.

[0028] The advantages of the invention concerning the increased rotation range of the optics of a monochromator in the monochromator chamber according to the invention, without increasing the volume and thus optimized evacuatability, are demonstrated by the exemplary embodiment. In terms of manufacturing technology, the invention corresponds to the state of the art and is therefore not

[0029] Disadvantage.

Claims

Patent claims 1. Monochromator chamber for a monochromator for X-rays, which is designed in the form of a cylinder or prism with a main axis and two side walls, at least comprising an incidence window for an incident X-ray beam and an exit window for an exiting X-ray beam, and wherein a direction of travel for an incident X-ray beam and an exiting X-ray beam is predetermined by the incidence and exit windows, characterized in that the incidence and exit windows are arranged such that the directions of travel for X-rays in the monochromator chamber determined by them enclose an angle y > 0° with the main axis of the monochromator chamber.

2. Monochromator chamber according to claim 1, characterized in that the angle y is > 20°.

3. Monochromator chamber according to claim 1 or 2, characterized in that the incident window is designed as a flange.

4. Monochromator for X-rays comprising at least one monochromator chamber according to one of claims 1 to 3 and a monochromator for X-rays, wherein the directions of travel for X-rays in the monochromator chamber, which are determined by the incidence and exit windows of the monochromator chamber, are congruent with the incoming and exiting X-ray beams in the beam path of the monochromator.

Images