Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/06—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diffraction, refraction or reflection, e.g. monochromators
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K2201/00—Arrangements for handling radiation or particles
  • G21K2201/06—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements
  • G21K2201/061—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements characterised by a multilayer structure
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K2201/00—Arrangements for handling radiation or particles
  • G21K2201/06—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements
  • G21K2201/062—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements the element being a crystal
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K2201/00—Arrangements for handling radiation or particles
  • G21K2201/06—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements
  • G21K2201/064—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements having a curved surface

Definitions

• the present invention relates in general to multilayer reflective optical assemblies with lateral gradient intended to reflect X-rays at a low angle of incidence.
• small angle of incidence angles of incidence less than a value of the order of 10 ° (the angle of incidence being defined with respect to the reflecting surface).
• the invention relates to a multilayer reflective optical assembly with a lateral gradient, the reflecting surface of which is intended to reflect incident X-rays at a low angle of incidence by producing a two-dimensional optical effect.
• the invention also relates to a method for producing such an optical assembly.
• the invention also relates to the generation and conditioning of X-rays in the context of angle dispersive X-ray reflectometry applications.
• two-dimensional optical effect is meant an optical effect using two different directions of space.
• It can for example be a focusing on a point (from a point source), or a collimation, of a beam whose rays are not parallel in any direction of space (conical beam divergent for example).
• the invention finds an application in the generation and conditioning of X-rays in the context of applications of angle dispersive X-ray reflectometry.
• Other non-limiting applications of the invention relate to X-ray generation, X-ray analytical applications such as diffraction, crystal diffraction, protein crystallography, texture analysis, film diffraction thin, stress measurement, reflectometry, X-ray fluorescence.
• the optics described in document US Pat. No. 6,041,099 are joined in a facing configuration ("Kirkpatrick-Baez device side by side") and have a multilayer coating.
• FIG. 1a shows such an optical assembly 33, which comprises two mirrors 331, 332 joined opposite one another, the surfaces of these two mirrors having curvatures centered on two axes perpendicular to one another.
• An object of the invention is to make it possible to produce optical assemblies as mentioned in the introduction to this text, and which are not affected by the drawbacks mentioned above.
• one aspect of the invention relates to the implementation of such optical assemblies for applications of angle dispersive X-ray reflectometry.
• an incident X-ray beam is conditioned on a sample to be analyzed so that the incident X-rays have a range of angles of incidence ⁇ on the sample considered (at the image spot level). ) on the order of a few degrees.
• Analysis of the intensity of the X-rays reflected as a function of the angle of incidence ⁇ makes it possible to determine characteristics such as the thickness, the structure, the density or the interfacial roughness of a thin film of material present on the sample.
• One such application relates in particular to the analysis of thin films for the microelectronics industry.
• the RX reflectometry technique is then particularly effective for the analysis of very thin layers (typically less than 50 nm) compared to so-called optical techniques such as for example ellipsometry (technique very widespread in the industry of semiconductors for thickness and structure controls of dielectric materials).
• the dispersion of the incidences of the rays of the beam arriving on the sample is obtained by the displacement of mobile elements of the measuring device.
• the measurements R ( ⁇ ) are carried out using an X-ray source and a plane monochromator, the angle dispersion being obtained by rotating the sample around a perpendicular axis. at the sample surface and the direction of X-ray propagation.
• FIG. 2a An example of such a known configuration is shown in Figure 2a.
• This figure shows an X-ray source S whose ray flux
• X is directed to a monochromator M.
• a sample E1 is carried by a sample holder E2.
• the sample E1 has on the surface a thin film E10 which it is desired to characterize by reflectometry.
• the rays from the reflection on the monochromator are directed towards the sample. And after their reflection on the sample, it is an X-ray detector D which will collect the reflected rays and allow their analysis.
• the arrow F illustrates the controlled movements of the sample holder and its sample.
• the measurements R ( ⁇ ) therefore require controlling the movements of mechanical elements of the device.
• This second type of method is known as the angle dispersive RX reflectometry method.
• FIG. 3a a one-dimensional view of a device 40 making it possible to perform angle dispersive RX reflectometry measurements is presented.
• This device 40 includes: • Means 41 for generating and conditioning X-rays.
• These means comprise an X-ray source and an optical assembly for conditioning the X-ray beam coming from said source, the optical assembly making it possible to condition an X-ray beam which one wishes to direct on a sample 42,
• the conditioning provided by the optical assembly of the means 41 corresponds to a controlled dispersion of the incidences of the X-ray beam directed towards the sample. It is thus sought that the X-rays arrive on the sample with an angular dispersion of a few degrees. According to a preferred application of the invention, it is sought to obtain an angular dispersion of the order of 2 ° or more.
• the beam reflected at the level of the sample is then collected by means of the detector 43.
• the optical conditioning produced by the optical assembly of the means 41 can correspond to a one-dimensional effect (for example focusing according to a single dimension) , or a two-dimensional optical effect.
• the detector 43 is of the PSD ("Position Sensitive Detector") type and comprises a sensor 430 of the CCD or photodiode type with a large number of pixels.
• PSD Position Sensitive Detector
• the detector 43 may be of the type * two-dimensional detector.
• a two-dimensional detector makes it possible to identify and group pixels corresponding to values of identical angles of incidence.
• pixels placed at different horizontal positions can correspond to identical angles of incidence . Indeed a certain divergence according to this second dimension
• This type of two-dimensional detector therefore makes it possible to take advantage of two-dimensional optics and in particular optics making it possible to collect a large flux along the two dimensions, which is the case of the optical assembly considered in the invention.
• To perform a two-dimensional conditioning of the beam for angle-dispersive RX reflectometry measurements it is known according to a first variant to exploit the diffraction of the beam from a source. X-rays from an optical assembly whose surface is a two-dimensional curved crystal.
• Such crystals make it possible to condition an initial beam according to an RX diffraction phenomenon which takes place according to Bragg's law.
• the Bragg condition for a crystal is of the form where n is the order of reflection, ⁇ the wavelength of the incident radiation for which the diffraction occurs, d the period of spacing between the atomic planes of the crystal involved in the diffraction and ⁇ B the angle of incidence on these same atomic planes which is necessary for the phenomenon of diffraction to occur.
• the two-dimensional curved crystals thus make it possible to produce a two-dimensional effect on the initial beam, with a view to achieving the desired conditioning.
• This conditioning can thus correspond to a focusing in two different directions.
• a particularity of crystals compared to the multilayer coating is that it is difficult to apply a gradient to such crystals in order to increase the useful surface of the crystal.
• each of the two mirrors of the KB device preferably comprises a multilayer coating with lateral gradient, which allows to reflect the initial beam X1 according to Bragg's law.
• optical assemblies can be associated with a relatively large size.
• the invention proposes, according to a first aspect, a multi-layer reflective optical assembly with lateral gradient, the reflecting surface of which is intended to reflect incident X-rays at low angle of incidence producing a two-dimensional optical effect, characterized in that said reflecting surface consists of a single surface, said reflecting surface being formed in two curvatures corresponding to two different directions
• optical assembly Preferred, but not limiting, aspects of such an optical assembly are the following:
• the two-dimensional optical effect is obtained by a single reflection of the incident rays on the optical assembly
• the multilayer is a multilayer with a gradient in depth
• Said reflecting surface is suitable for reflecting rays of the Cu-K ⁇ lines
• the reflecting surface has a geometry of substantially toroidal shape, “the reflecting surface has a geometry of substantially paraboloidal shape,
• the reflecting surface has a geometry of substantially ellipsoidal shape
• the reflecting surface has a geometry of substantially circular shape in a first direction, and elliptical or parabolic in a second direction,
• the reflecting surface has a sagittal radius of curvature less than 20 mm
• a window opaque to X-rays and comprising an opening is associated at the input and / or output of the optical assembly, to control the flow of input and / or output of the optical assembly, • the windows are removable,
• the window openings are sized to achieve a flux / divergence radiation compromise.
• the invention also provides a method of manufacturing an optical assembly according to one of the above aspects, characterized in that the method comprises coating a substrate already having a curvature, and the curvature of this substrate in a second different direction.
• the substrate already has a curvature which corresponds to the sagittal direction of the optical assembly
• the substrate itself is constituted, starting from an element in the form of a tube, cone, or pseudo-cone already having a curvature in a direction perpendicular to the axis of the tube, the cone or the pseudocone,
• the element in the form of a tube, cone or pseudo-cone has a roughness of less than 10 angstroms rms and a radius of sagittal curvature of less than 20mm,
• the element is a glass tube with circular cross section
• the glass is of the Duran type (registered trademark)
• the constitution of the substrate comprises cutting the tube in the longitudinal direction of the tube, so as to obtain a substrate in the form of an open cylinder ,
• the coating is made to constitute a multilayer before bending the substrate,
• the substrate is bent to conform to the desired geometry before being coated to form a multilayer,
• the optical assembly is coupled to a filter, to ensure the attenuation of the unwanted spectral bands while guaranteeing sufficient transmission of a band of predetermined wavelength for which it is desired to reflect the incident X-rays,
• the filter is a 10 ⁇ m nickel filter
• the invention proposes an X-ray generation and conditioning device for angle dispersive X-ray reflectometry applications comprising an optical assembly according to one of the above aspects coupled to an X-ray source. so that the X-rays emitted by the source are conditioned in two dimensions in order to adapt the beam emitted by the source to a sample, the X-rays having different angles of incidence on the sample considered .
• Preferred, but non-limiting aspects of such a device are the following:
• the dispersion of the angle of incidence on the sample corresponds substantially to the angular dispersion along the sagittal dimension of the beam reflected by the optical assembly,
• the optics are oriented with respect to the sample in such a way that the normal at the center of the optical assembly is substantially parallel to the surface of the sample,
• the capture angle at the level of the sample is greater than 2 ° along a first dimension corresponding to the sagittal dimension of the optical assembly and of the order of 1 ° along a second dimension corresponding to the southern dimension of l optical assembly, the optical assembly being positioned in such a way that the angle of incidence of the X-rays on the sample is greater than 2 °, the sample being placed at a distance greater than 15 cm from the optical assembly.
• Figure 1 is a schematic representation of a first embodiment of an optical assembly according to the invention, for performing a two-dimensional focusing of an incident beam of X-rays
• Figure 2 is a similar view showing a second embodiment of an optical assembly according to the invention, making it possible to collimate an incident beam of X-rays
• FIG. 3 is a similar view showing a third embodiment of an optical assembly according to the invention, in which a small divergence in the reflected flux is sought,
• Figure 4 is a schematic representation of an angle dispersive RX reflectometry device according to the invention (the X-ray detector is not shown in this figure for reasons of clarity), • Figures 5a and 6a show schematically highlighting the elongation stresses related to KB type optical assemblies known, which are necessary to increase the angular dispersion of the reflected beam in the directions transverse to the direction of propagation of the beam.
• the southern direction corresponds to the mean direction of propagation of this beam (and more precisely to the mean direction between the mean directions of propagation of the beam before and after its reflection on the optical assemblies which will be discussed),
• the sagittal direction corresponds to a horizontal transverse direction of this southern direction (the vertical being here defined by the average normal to the part of the reflecting surface of the optical assemblies which will be described and which is actually used to reflect the beam of X-rays incident).
• an optical assembly 10 for reflecting incident X-rays from a source S of X-rays.
• the source S may in particular be of the X-ray tube, rotating anode, or even X-ray source type with micro focus.
• the optical assembly 10 comprises a multilayer structure formed on a substrate (for example made of glass), which defines a reflecting surface for the incident X-rays.
• the reflecting surface of this optical assembly has a particular geometry.
• this reflecting surface is shaped according to two curvatures corresponding to two different directions. And this reflective surface thus presents significant differences compared to reflective surfaces of the type of those used in optical assemblies such as those taught by the document US Pat. No. 6,041,099:
• the reflecting surface is a single reflecting surface, unlike what is the case for optical assemblies in which two different elementary mirrors have been assembled,
• This reflecting surface is regular (this term signifying in the present text that the reflecting surface does not present any second order discontinuity (angular points or edges - protruding or hollow - etc.),
• the reflecting surface of the optical assembly according to the invention has a curvature Rx in the southern X direction, and a curvature Ry in the sagittal Y direction.
• FIG. 1 makes it possible to visualize these radii of curvature, two curves Cx and Cy having been represented to show the shape of the curves defined by the radii of curvature Rx and Ry respectively.
• Each of the two radii of curvature can be constant, or vary along its associated curve.
• Each of the curves Cx, Cy can thus be a circle, but also an ellipse, a parabola, or another curve (open or closed).
• the reflecting surface of the optical assembly 10 does not have a simple spherical shape (that is to say that the radii Rx and Ry are not both equal and constant).
• FIG. 1 represents the case in which each curve Cx, Cy produces a one-dimensional focus.
• Rx and Ry are different, but each is constant (the curves Cx and Cy are circles).
• the reflecting surface of the optical assembly thus has a toroidal geometry.
• this optical assembly is one-piece (not requiring delicate assembly).
• the reflective surface is unique and regular. It has been said that the reflecting surface of the optical assembly 10 is defined by a multilayer.
• This multilayer (like all the multilayers which will be discussed in this text) comprises at least a "lateral gradient”.
• This characteristic makes it possible to effectively reflect X-rays having different local incidences with respect to the reflecting surface.
• lateral gradient multilayer is understood here to mean a multilayer whose layer structure is adapted so that the Bragg condition is respected at all points of the useful surface of the mirror.
• n order of reflection
• ⁇ wavelength of the incident radiation
• d period of the multilayer
• ⁇ angle of incidence on the surface of the multilayer.
• the gradient is obtained by varying the period of the multilayer locally, in a suitable manner.
• This type of multilayer structure with lateral gradient thus makes it possible to increase the solid angle of collection of the optical assembly, which leads to a higher reflected flux compared to single-layer mirrors operating in total reflection, for a geometry of identical optics.
• the presence of a lateral gradient also makes it possible to overcome the limits of certain known configurations, such as the configurations using the Rowland circle for which the distance between the source and the optics and the distance between the optics and the sample are identical, and the variations of angles of incidence on the optics can be small for optics of small sizes.
• the multilayer of the various embodiments of the invention may also have a depth gradient.
• Such a depth gradient makes it possible to fulfill the Bragg conditions for fixed angles of incidence and variable wavelengths, or vice versa.
• the wavelength tolerance of the optical assembly is used (tolerance in ⁇ ).
• a tolerance on the wavelength corresponding indeed - within the framework of the Bragg condition - to a tolerance on the angle of incidence it is possible at constant wavelength of the incident beam to collect and reflect a incident light flux whose rays of the same wavelength have different local incidences.
• FIG. 2 another preferred embodiment of the invention has been shown, illustrated by an optical assembly 20.
• the reflecting surface of the multilayer of this optical assembly is shaped in the respective directions X and Y according to two curves Cx and Cy respectively parabolic and circular, each of these curves producing a collimation according to its associated X or Y direction.
• a parallel collimation in all directions of space is thus generated from the divergent incident beam.
• optical assemblies composed of a multilayer mirror (with lateral gradient, and optionally also with depth gradient), the reflecting surface of which may have one of various aspherical complex shapes. It is thus possible in particular to give this reflecting surface one of the following geometries: geometry of substantially toroidal shape, geometry of substantially paraboloidal shape, geometry of substantially ellipsoidal shape, • geometry of substantially circular shape in a first direction (in particular the direction sagittal), and elliptical or parabolic in a second direction (in particular the southern direction).
• the lateral gradient may in particular extend along the southern direction of the incident X-rays.
• the period of the multilayer may be adapted to reflect in particular the radii of the Cu-K ⁇ lines.
• an optical assembly 30 according to the invention, provided with two end walls 31 and 32, positioned respectively at the entry section and the exit section of the radiation to be reflected. by this optical assembly.
• Each wall 31, 32 has an opening (respectively 310, 320) allowing the X-ray radiation to pass, the walls being moreover opaque to the X-rays.
• the walls could for example be made of lead. And it is possible to adjust the shape and size of each opening
• the walls 31 and 32 can be designed to be removable, for example by being screwed onto the horizontal transverse edges of the optical assembly as shown in FIG. 3.
• optical assemblies can be flexibly adapted to seek, if necessary, a desired flux / divergence compromise.
• each wall associated with its opening thus constitutes a "window" allowing the X-rays to pass.
• the surface roughness specifications for substrates of multilayer X-ray mirrors usually correspond to roughness not to exceed a maximum value of the order of 10 angstroms rms (root mean square)
• the requested surface condition is obtained without any particular treatment, by using to form the optical assembly a substrate which already has a curvature in a direction of curvature.
• the direction in which the substrate already has a curvature preferably corresponds to the sagittal direction of the optical assembly, once it is manufactured and placed relative to the X-ray source (this direction being as we said defined with respect to the incident radiation, but which can also be defined with respect to the optical assembly itself insofar as the optical assembly is intended to be oriented in a specific manner with respect to the incident radiation).
• a substrate has a face which corresponds to the face of the optical assembly which will carry the reflecting surface. This face of the substrate will be called “optical face”.
• a substrate which already has a curvature (in a direction which will preferably be corresponded to the sagittal direction of the optical assembly), and this substrate is curved in a second different direction. (preferably corresponding to the southern direction of the optical assembly).
• the optical face of the substrate is also coated with a multilayer. This coating can be carried out before the curvature of the substrate, or after.
• an optical assembly is thus obtained.
• a substrate having the desired curvature (in shape and in value (s) of radius of curvature), and by bending it as desired, an optical assembly can be obtained having the desired geometry.
• the substrate itself, in particular starting from an element (in particular out of glass) such as a tube, a cone, or even a pseudo-cone (which is defined here as a surface of revolution generated by the revolution along a curve such as an ellipse of a generative line oblique to its axis of revolution and intersecting it in space).
• an element in particular out of glass
• a pseudo-cone which is defined here as a surface of revolution generated by the revolution along a curve such as an ellipse of a generative line oblique to its axis of revolution and intersecting it in space.
• the tube can have a circular cross section, but also elliptical, or correspond to any closed curve.
• an element can also be an open cylinder whose directrix is an open curve such as a portion of a parabola.
• the starting element has a curvature in a direction which preferably corresponds to the sagittal direction of the optical assembly which it is desired to manufacture.
• such a substrate can in particular be obtained from a glass tube whose cross section is circular.
• the substrate from which the optical assembly will be produced and which has a curvature in a direction can be obtained in particular by:
• Such a substrate will then be curved in a direction (preferably southern), with the desired curvature, to obtain the optical assembly. And it is specified that it is possible - in this embodiment as in the others - to proceed first to the curvature of the element (here the cut tube), and then to the coating.
• the multilayer thus formed is a multilayer with lateral gradient (and possibly also with depth gradient).
• the glass tube is cut in the longitudinal direction of the tube by making a section in a direction parallel to the axis of symmetry of the tube (and may even include this axis to form a half-tube), so as to obtain a substrate in the form of an open cylinder.
• the director of this open cylinder therefore has in this preferred embodiment the shape of a part of a circle - for example a semicircle.
• This longitudinal cutting is followed by another cutting to size the optic in length.
• the coated substrate After having coated the substrate with the multilayer, the coated substrate is bent in the second desired direction, which corresponds to the southern direction, to conform the surface of the multilayer according to the desired geometry.
• a cylindrical substrate can be formed, the director of which has substantially the shape of a part of a circle, then the coating is carried out with a such substrate, and the curvature of this substrate in a direction not included in the plane of the director of the cylinder of said substrate (in particular along the direction of the generatrix of the cylinder).
• substrates, used subsequently for the multilayer coating having a very good surface condition (roughness not exceeding 10 angstroms rms), and small radii of sagital curvature (less than 20 mm ).
• the cylindrical substrate is first curved, then the coating is carried out to form the multilayer on the surface thus shaped.
• the coating can be carried out with all types of materials making it possible to produce reflective multilayers for X-rays.
• this coating can implement any type of process known for this purpose, for example spraying (possibly assisted by plasma) or another type of vacuum deposition. It is also specified that for applications requiring high spectral purity, the optical assembly intended to reflect X-rays may be coupled to a filter made from a thickness and of an appropriate material, to ensure the attenuation of the unwanted spectral bands while guaranteeing sufficient transmission of a band of predetermined wavelength for which it is desired to reflect the incident X-rays.
• a 10 ⁇ m nickel filter can be used to attenuate with a factor 8 the K ⁇ copper line (0.139 nm) while retaining sufficient transmission for K ⁇ lines (greater than 60%). This filtering function is added to the "natural monochromatization" obtained using the multilayer and can therefore allow, for applications where spectral purity is a priority, to increase the performance of the multilayer optics described in the invention.
• FIG. 4 represents a device 60 making it possible to carry out measurements of type R ( ⁇ ) for this type of application.
• the X-ray detector normally intended for detecting rays from reflection on the sample is not shown in this figure, for the sake of clarity. With reference to FIG. 4, it is specified that the angular dispersions of the beam X2 reflected on the optical assembly 61 are not representative.
• the device 60 comprises a source S of X-rays, which emits an initial beam X1.
• the initial beam X1 originating from the source is directed towards the optical assembly 61, the reflecting surface of which is shaped according to two curvatures corresponding to two different directions.
• This optical assembly 61 is thus able to produce on the initial beam X1 a two-dimensional optical effect, to generate a beam X2 which has a controlled angular dispersion.
• the beam X2 is then directed towards the sample 62 for which it is desired to characterize the reflectivity, for example for applications as mentioned at the beginning of this text in connection with measurements of type R ( ⁇ ).
• the different elements of the device 60 are fixed for all of the measurements R ( ⁇ ) for a given analysis spot on the sample.
• optical assembly 61 makes it possible to generate a beam X2 conditioned in a desired manner according to a two-dimensional effect (which is typically a two-dimensional focusing).
• the optical assembly 61 conditions the beam X2 in such a way that a high convergence angle is obtained at the level of the sample, and in particular along a dimension which corresponds to the sagittal dimension of the optical assembly 61 ( i.e. direction Y in Figure 4).
• the capture angle at the level of the sample (that is to say the angle of convergence of the optics) is:> greater than 2 ° along a dimension (corresponding to the sagittal dimension of the optics), and of the order of 1 ° according to another dimension (corresponding to the southern dimension of the optics),
• this positioning is defined in such a way that the dispersion of angles of incidence of the X-rays arriving on the sample is greater than 2 °.
• This device 60 makes it possible to carry out rapid angle dispersive RX reflectometry measurements, since it does not involve displacement of a mechanical element.
• optical assembly 61 which ensures the angular dispersion of the beam X2 by conditioning this beam so as to adapt it to the level of the sample so that the X-rays arriving on this sample have different angles of incidence at the level of the image spot considered (focal point of the optical assembly on the sample).
• the optical assembly 61 therefore has a single reflecting surface, this surface being curved along two dimensions with a first curvature in the sagittal direction and a second curvature in the southern direction.
• Figure 4 gives a more detailed illustration of this optical assembly.
• it is an optical assembly making it possible to focus in 2 dimensions with a first curvature in the direction Y (circular curvature CY) and a second curvature in the direction X (circular curvature CX).
• the optics therefore have a toroidal shape.
• the optical assembly 61 may have a toroidal shape or an ellipsoidal shape in the case of two-dimensional focusing.
• the optical assembly 61 may also have a paraboloidal shape in the case of a two-dimensional collimation. According to another variant, the optical assembly 61 may also have a circular curvature along one dimension, for example along the sagittal direction, and a parabolic curvature along another dimension, for example along the southern direction.
• the optical assembly 61 has a multilayer coating with a lateral gradient (that is to say in the southern direction which corresponds to the direction X in FIG. 4).
• optical assembly 61 has a large useful collection area, which makes it possible to obtain a high convergence angle at level of the sample, in particular according to the sagittal dimension of the optics.
• the useful collection area of the optical assembly is the useful collection area of the optical assembly
• 61 can thus have in the sagittal direction a dimension of the order of 1 cm for focusing distances of the order of 200 mm.
• the dimension mentioned above corresponds to the length of the straight line obtained by joining the two extreme points of the useful collection surface in the sagittal direction.
• the useful collection surface can correspond to a portion according to the sagittal dimension of the order of a quarter circle or about 1cm, which corresponds to a capture angle at the level of the sample of the order of
• the sample is placed at focusing distances (distance between the optical assembly 61 and the sample) greater than 150 mm.
• the focusing distances can be of the order of 300 mm to 200 mm.
• the orientation of the optical assembly 61 relative to the sample will thus be adapted so that the dispersion in angles of incidence of the X-rays on the sample is greater than 2 °.
• the orientation of the optical assembly 61 is defined as the angular position of this optical assembly for a given rotation around its optical axis (axis parallel to the southern direction).
• a privileged positioning of the elements of the device consists in orienting the optical assembly in such a way that the dispersion of angles of incidence on the sample corresponds substantially to the angular dispersion along the sagittal dimension (the direction Y in FIG. 4) of the X2 beam reflected at the optical assembly.
• a privileged positioning thus consists in orienting the optical assembly in such a way that the average normal to the useful surface of the optical assembly (or the normal to the center of the optics) is substantially parallel to the surface of the sample.
• the average incidences on the sample are grazing and in the case of very grazing incidences (average incidence of the order of 1 °) the orientation of the optical assembly 61 can be described as such that:
• the mean normal of the optical assembly is substantially parallel to the surface of the sample 62
• the sagittal direction of the optical assembly 61 is substantially perpendicular to the surface of the sample 62,
• the southern direction of the optical assembly 61 is substantially parallel to the surface of the sample 62.
• the optical assembly 61 will not be oriented in such a way that the average normal to the useful surface of the optical assembly 61 is substantially perpendicular to the surface of the sample. 62 if we consider a grazing incidence (the dispersion of angles of incidence on the sample 62 would then correspond substantially to the angular dispersion of the beam X2 in the southern direction).
• the optical assembly makes it possible to collect a flux important and according to a preferred application, the angular dispersion of the beam X2 reflected is of the order of 1 ° along this southern direction (direction X in FIG. 4).
• the optical assembly 61 therefore makes it possible to obtain a high angle of incidence dispersion at the level of the sample while conditioning a maximum of flux at the level of the sample.
• the optical assembly 61 in fact makes it possible to obtain, for a given length (in the southern direction), a collection surface which is larger in the sagittal direction than what one would obtain with a configuration implementing packaging by a KB type optics.
• the angular dispersion of the beam treated by the useful surface of the optical assembly is higher in the sagittal direction, and a high angular dispersion is obtained on the sample.
• obtaining an equivalent angular dispersion with optical assemblies of type KB would require the elongation of the optical assembly in the direction Y.
• any incident ray must indeed strike the optical assembly in a particular zone (corresponding to the hatched zones of the mirrors of FIGS. 5a and 6a) to undergo a double reflection.
• the useful collection surface of the mirror along the sagittal dimension can describe a portion such as a quarter or even a semicircle, this which corresponds to a capture angle at the level of the sample according to the sagittal dimension which is important.
• the possibility for the optical assembly 61 to increase the useful collection surface in the sagittal direction is due to the fact that the angle of incidence on the optics of the X-rays coming from the same source point varies very little in this direction (direction Y in Figure 4).

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