Apparatus for elemental analysis of a sample to be examined by laser-induced breakdown spectroscopy, comprising a sample holder

Abstract

The present invention relates to an apparatus for the elemental analysis of a target sample, comprising a base 1 having a flat surface 10 and intended to support a target sample 2, a system 3 for generating a laser beam 30 intended to impinge on the target sample 2 in a direction perpendicular to the flat surface 10 of the base 1 in order to generate a plasma P giving rise to an emission of light 40, means 4 for collecting the emission of light 40, and a sample holder 5 intended to rest on the base 1.

Description

[Technical Field]

[0001] The present invention relates to the field of high resolution mapping and analysis of elements in solids.

[0002] More particularly, but not exclusively, the present invention relates to an apparatus for the qualitative and quantitative analysis of the elemental chemical composition of solid samples.

[0003] The invention is particularly applicable to the elemental analysis of hydrogen and oxygen by optical emission spectroscopy on laser-produced plasmas in the field of the nuclear industry or in the aeronautical or space industry. [Background technology]

[0004] Elemental analysis of metal samples can be essential in applications such as characterizing equipment exposed to radioactive sources or characterizing the aging capabilities of equipment used in particularly harsh environments, such as aircraft or spacecraft.

[0005] More specifically, it may be necessary to be able to map these elements in the sample being analyzed, where mapping means identifying the elements that make up the sample being analyzed and, optionally, the distribution of the various elements and the chemical bonds between them.

[0006] Such analyses can be particularly useful in studying metal embrittlement by hydrogen, or fuel cladding aging in the presence of oxygen, or fuel cladding embrittlement caused by the formation of hydride compounds, which promote crack propagation.

[0007] There are a variety of known methods for mapping the elements present in a sample.

[0008] One of these methods is elemental analysis by optical emission spectroscopy on laser-produced plasma, a technique performed in natural air, also referred to by the English acronym "LIBS," which stands for "laser induced breakdown spectroscopy."

[0009] The method is particularly applicable to the in situ examination and characterization of samples of analyte moieties.

[0010] A method and apparatus for elemental analysis by optical emission spectroscopy on laser-produced plasma in the presence of argon is described in US Pat. No. 5,649,999.

[0011] Such an analytical device - a stand intended to support the sample under consideration; - a system for generating a laser beam intended to impinge on the sample under consideration according to a direction perpendicular to the stand and to generate a plasma that generates light emission; - means for collecting luminescence; Equipped with.

[0012] The laser beam generated by the generating system is shaped by the shaping module and then applied to the sample under study via focusing optics.

[0013] A plasma is then generated upon impingement of the laser beam on the sample under study, this plasma producing an optical emission that is analyzed to map the elements that make up the sample under study.

[0014] Collection of the plasma's emitted light is then performed by a collection means.

[0015] By moving the sample under study relative to the laser beam, it is possible to access the distribution of concentrations of the constituent elements on the surface of the sample, which makes it possible to establish an elemental mapping.

[0016] The device described in the aforementioned document comprises means for transporting the sample to be analyzed.

[0017] More specifically, the sample is placed within micrometer margins on a plate, which is for example motorized, allowing for minute movements along two directional axes.

[0018] The focus produced by the focusing optics is an important parameter, since this focus must be maintained throughout the analysis of the surface of the sample under consideration.

[0019] If the surface of the sample to be analyzed is sufficiently flat (a surface is considered sufficiently flat if its relief does not have a height difference greater than the depth of field of the focusing optics), and if it is ensured that this surface is perfectly perpendicular to the laser beam, there will be no focusing problems.

[0020] If the sample surface is not flat and / or is not perfectly perpendicular to the laser beam, adjustments of the focus must be made as the analysis progresses.

[0021] A similar device is also known, as described in Patent Document 2.

[0022] The device comprises an autofocus system that makes it possible to compensate for such flatness and perpendicularity defects of the surface of the sample under consideration relative to the laser beam, for which purpose it implements a sensor that measures any flatness defects of the sample and a motorized part of the sample holder that can orient the sample holder in a direction depending on the measured flatness defects.

[0023] This design solves the problem of having to focus the laser beam, but introduces inherent complexity into the device. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] International Publication No. 01 / 33202 [Patent Document 2] International Publication No. 2016203163 Summary of the Invention [Problem to be solved by the invention]

[0025] In particular, it is an object of the present invention to overcome the drawbacks of the prior art.

[0026] More specifically, the object of the present invention is to provide an apparatus for the elemental analysis of a sample under consideration of the type described above, which makes it possible to address defects in the flatness and perpendicularity of the surface of the sample under consideration relative to the laser beam in a less complex manner than the methods proposed by the prior art. [Means for solving the problem]

[0027] For this purpose, and others which will become apparent later, a stand having a flat surface and intended to support the sample to be studied; - a system for generating a laser beam intended to impinge on the sample under consideration according to a direction perpendicular to the flat surface of the stand and to generate a plasma that generates light emission; - means for collecting luminescence; An apparatus for elemental analysis of a sample under consideration, comprising: The apparatus includes a sample holder, the sample holder comprising: - a lower flat surface intended to rest on a flat surface of a stand; a cavity intended to receive a sample; - at least one shoulder forming a bearing surface directed towards the cavity, the bearing surface being inscribed in a plane parallel to the lower flat surface of the sample holder; - elastic return means configured to press the sample against the bearing surface; a cylindrical block having a cavity and a shoulder(s); - a base having a lower planar surface and holding means for holding a block on the base, the holding means comprising two jaws for clamping the block, each having a clamping surface whose generatrix extends perpendicular to the lower planar surface; This is achieved by the invention relating to an apparatus, characterized in that it comprises:

[0028] The apparatus according to the invention addresses the flatness and perpendicularity defects mentioned above in a less complex manner than the methods proposed by the prior art (autofocus).

[0029] This is because the design of the device according to the invention makes it possible to ensure that the surface of the sample under consideration extends perpendicularly to the laser beam generated by the generation system of the device.

[0030] The sample holder presses the sample against the bearing surface, with the surface of the sample then extending in a plane parallel to the lower flat surface of the sample holder, and since the lower flat surface of the sample holder rests on the flat surface of the stand, the surface under consideration of the sample extends parallel to the flat surface of the stand and therefore perpendicular to the laser beam, which extends perpendicular to the flat surface of the stand during operation of the device.

[0031] Due to the fact that the surface of the sample to be analyzed is pressed securely against the shoulder, there are no focusing problems when examining the surface of the sample to be examined. The sample holder of the device according to the invention forms a simple mechanical solution, in particular a simpler mechanical solution than the use of an autofocus.

[0032] For example, the cylindrical block is obtained by precision machining.

[0033] This cylindrical block makes it possible to provide a surface that extends parallel or perpendicular to the lower flat surface of the sample holder and the flat surface of the stand when the sample holder is installed in the device.

[0034] More specifically, in that case, the radially outer surface of the block, and more specifically the generatrices of this surface, extend perpendicular to the flat surface of the stand, whereas the bottom surface of the cylinder extends parallel to the flat surface of the stand.

[0035] Each of the two clamping jaws of the block has a clamping surface whose generatrices extend perpendicular to the lower flat surface, and these clamping jaws ensure that they make flat contact with the radially outer surface of the block during clamping, thereby ensuring that clamping does not cause angular tilt of the central axis of the cylindrical block relative to the flat surface of the stand.

[0036] Conversely, fastening using screws that exert a point stress perpendicular to the central axis of the cylindrical block on the radially outer surface of the cylindrical block can result in an offset that distorts the measurement.

[0037] Preferably, the cylindrical block is an axisymmetric cylinder.

[0038] Advantageously, the shoulder has an annular shape.

[0039] Such a shoulder makes it possible to form a continuous bearing surface against which the sample can be pressed.

[0040] According to an advantageous feature, the sample holder comprises a stop connected to the block and forming a support for the elastic return means.

[0041] Such a stop being separate from the block makes positioning of the sample within the block, and also the positioning of the elastic return means, and ultimately the positioning of the stop, easier to perform and helps to ensure proper positioning of the sample relative to the axis of the laser beam.

[0042] Preferably, the elastic return means have at least two upper contacts intended to come into contact with the sample and at least two lower contacts intended to abut against the stops.

[0043] In this way, it is ensured that the support provided by the elastic return means against the stop and the force applied by the elastic return means act in an evenly distributed manner to properly press the sample against the bearing surface formed by the shoulder.

[0044] According to an advantageous embodiment, the elastic return means have the form of a wave spring washer.

[0045] Such a wave spring washer is suitable for achieving a resilient return that ensures proper pressing of the sample against the bearing surface.

[0046] Even more preferably, the spring washer has an S-shaped profile in side view.

[0047] Such a spring washer completely ensures that the sample is properly pressed against the bearing surface.

[0048] The present invention provides a method for elemental analysis of a sample under study by optical emission spectroscopy on a laser-produced plasma, comprising the steps of preparing the sample and positioning it on a stand for its analysis, The step of preparing the sample includes a sub-step of grinding the sample to form a flat surface to be examined, and the positioning step includes the use of a sample holder, the sample holder comprising: - a lower flat surface intended to rest on a flat surface of a stand; a cavity intended to receive a sample; - at least one shoulder forming a bearing surface directed towards the cavity, the bearing surface being inscribed in a plane parallel to the lower flat surface of the sample holder; - elastic return means configured to press the sample against the bearing surface; a cylindrical block having a cavity and a shoulder(s); - a base having a lower planar surface and holding means for holding a block on the base, the holding means comprising two jaws for clamping the block, each having a clamping surface whose generatrix extends perpendicular to the lower planar surface; The present invention is characterized in that it comprises: The positioning step includes: - inserting the sample into the sample holder and positioning the planar surface under consideration on a bearing surface of the sample holder inscribed in a plane parallel to the lower planar surface of the sample holder intended to rest on the planar surface of the stand; - adding elastic return means for pressing the flat surface to be examined of the prepared sample against a bearing surface; The present invention also relates to a method comprising:

[0049] This analytical method can be carried out by the device according to the invention described above.

[0050] This method of analysis ensures proper positioning of the sample relative to the axis of the laser beam.

[0051] Other characteristics and advantages of the invention will appear on reading the following description of various preferred embodiments of the invention, given by way of illustrative and non-limiting example, and will also become apparent from the accompanying drawings, in which: [Brief explanation of the drawings]

[0052] [Figure 1]1 is a schematic representation of a side view of an apparatus for elemental analysis of a sample under consideration according to the invention, comprising in particular a sample holder resting on a stand; [Figure 2] 1 is a schematic cross-sectional view of a sample holder of a device according to the invention, comprising a block for receiving the sample, elastic return means and a stop that allows the sample to be pressed within the block, as well as a base and means for holding the block on the base. [Figure 3] 1 is a schematic diagram of a cross-sectional view of a block that receives a sample and contains therein a resilient return means and a stop. [Figure 4] FIG. 1 is a schematic cross-sectional view of a block alone. [Figure 5] FIG. 2 is a schematic cross-sectional view of a stopper. [Figure 6] 3 is a schematic representation of a profile view of a resilient return means, in particular in the form of a wave washer; FIG. [Figure 7] FIG. 10 is a schematic diagram of a top view of the sample holder, particularly showing the means for holding the block on the base. DETAILED DESCRIPTION OF THE INVENTION

[0053] Referring to Figure 1, the setup for elemental analysis of the samples under study is shown.

[0054] The analysis device is of the type that projects a laser beam 30 onto the sample 2 under consideration to generate a plasma P that generates an emitted light 40 for collection and analysis purposes.

[0055] With continued reference to FIG. 1, the apparatus a stand 1 intended to support a sample 2 to be studied, the stand 1 having a flat surface 10; a system 3 for generating a laser beam 30 intended to impinge on a sample 2 under consideration and generate a plasma P generating an emission of light 40; - means for collecting luminescence; a sample holder 5 intended to hold a sample 2 to be studied above the stand 1, the sample holder 5 resting on the stand 1, more particularly on a flat surface 10 of the stand 1; Equipped with.

[0056] The system 3 for generating a laser beam 30 is configured to emit the laser beam 30 according to a direction perpendicular to the flat surface 10 of the stand 1 .

[0057] The system 3 for generating a laser beam 30 comprises a laser source for generating a laser beam, means for shaping the laser beam and optical means for focusing the laser beam.

[0058] The generating system 3 is configured so that the focus of the laser beam 30 is adapted to the sample 2 under consideration.

[0059] This focal point is defined in part by the depth of field within which the surface of the sample 2 under consideration that is impinged by the laser beam 30 should be located.

[0060] The means 4 for collecting the emitted light 40 then comprise, for example, an optical fiber 41 directed towards and positioned closest to the plasma P to collect the emitted light 40 .

[0061] The sample holder 5 is described in more detail below.

[0062] Referring to Figures 2, 3 and 7, the sample holder 5 is - Block 54, - a base 55; - means 56 for holding the block 54 on the base 55; Equipped with.

[0063] In a simple design, the sample holder 5 is a lower flat surface 50 intended to rest on the flat surface 10 of the stand 1; a cavity 51 intended to receive a sample 2; a bearing surface 520 oriented towards the cavity and inscribed in a plane parallel to the lower flat surface 50 of the sample holder 5; - elastic return means 53 configured to press the sample 2 against the bearing surface 520; Equipped with.

[0064] According to this embodiment, the lower flat surface 50 is provided by a base 55 .

[0065] When the sample holder 5 is placed on the stand 1 , the lower flat surface 50 of the base 55 is in flat contact with the flat surface 10 of the stand 1 .

[0066] A cavity 51 intended to receive the sample 2 is provided by a block 54 .

[0067] The sample holder 5 also comprises at least one shoulder 52 forming a bearing surface 520 .

[0068] In this case, the bearing surface 520 is formed by one single shoulder 52 .

[0069] This shoulder 52 is provided by a block 54 intended to receive the sample 2 in its cavity 51 .

[0070] In this case, the shoulder 52 has an annular shape and therefore corresponds to the inner shoulder of the block 54, which according to the present embodiment is cylindrical, more particularly cylindrical and axisymmetric about a central axis.

[0071] Thus, the bearing surface 520 extends from the peripheral wall of the block 54 in the direction of the central axis of the axisymmetric cylindrical block 54 .

[0072] The axisymmetric cylindrical block 54 is a radially outer surface 541; a lower surface 540 inscribed in one of the two bases corresponding to an axisymmetric cylindrical shape; an upper surface 542 inscribed in the other of the two axisymmetric cylindrical bases; It has.

[0073] The cavity 51 is open to the lower surface 540 .

[0074] The block 54 has an opening 543 centered on an upper surface 542 and opening into the cavity 51 to allow the laser beam 30 to impinge on the sample 2 .

[0075] Being cylindrical, all of the generatrices of the radially outer surface 541 extend perpendicular to the lower surface 540 and the upper surface 542 .

[0076] Similarly, these generatrix lines extend perpendicular to the plane in which bearing surface 520 is inscribed.

[0077] The block 54 is provided with an internal thread 544, the functionality of which will be explained in more detail below.

[0078] Referring to FIGS. 2, 3 and 5, the sample holder 5 includes a stopper 57 .

[0079] This stopper 57 is connected to the cylindrical block 54 and forms a support for the elastic return means 53. In particular, this stopper 57 has an annular shape.

[0080] The fastener 57 is connected to the cylindrical block 54 by being screwed into the cavity 51 .

[0081] For this purpose, the fastener 57 has an external thread 571 which can be screwed complementarily into the internal thread 544 .

[0082] The stopper 57 and the block 54 are configured such that by screwing the stopper 57 into the cavity 51, the upper surface 570 of the stopper 57 is in a plane parallel to the plane inscribed by the bearing surface 520.

[0083] In order for the block 54 and the stop 57 to have a strictly geometric shape, in particular having front and side surfaces inscribed in parallel or perpendicular planes, these two parts are manufactured by high-precision machining or 3D printing.

[0084] 2, 3 and 6, the resilient return means 53 has the form of a wave spring washer.

[0085] More specifically, the spring washer has an S-shaped profile when viewed from the side.

[0086] Such a wave spring washer enables the elastic return means 53 to have at least two upper contacts 531, in this case three upper contacts 531 intended to come into contact with the sample 2, and at least two lower contacts 532, in this case three lower contacts 532 intended to abut against the stop 57, more particularly against the upper surface 570 of the stop 57.

[0087] Due to the profile view of Figure 6, only two upper contacts 531 and two lower contacts 532 are visible, but it can be easily seen that the washer has a third upper point 531 behind the upper point 531 located in the right part of the figure, and a third lower contact 532 behind the lower contact 532 located in the left part of the figure.

[0088] 2 and 7, the retaining means 56 will now be described in more detail below.

[0089] These holding means 56 are fixed on the base 55. The holding means 56 comprise two jaws 561 that clamp the block 54.

[0090] Each jaw 561 has a clamping surface 562 the generatrices of which extend perpendicular to the lower planar surface 50 provided by the base 55 .

[0091] More specifically, the holding means 56 is configured so that the two clamping jaws 561 can be moved towards each other while maintaining the generatrices of the clamping surfaces 562 perpendicular to the lower flat surface 50 .

[0092] To this end, and with more particular reference to the embodiment of Figure 7, the holding means 56 comprises a hinge 563 defining a pivot axis of one of the jaws relative to the other of the jaws 561, which extends perpendicular to the lower planar surface 50. This pivot axis extends perpendicular to the lower planar surface 50. According to another preferred embodiment not shown, the holding means 56 is at least partly made from an elastically deformable material and comprises a thickness reduction at the location of the hinge 563. In this way, the two jaws can be spaced apart from each other to allow the block 54 to be inserted.

[0093] In addition, the holding means 56 comprises a bolt 564 coupled to the two clamping jaws 561 so as to allow the two clamping jaws 561 to be brought closer together.

[0094] Such clamping means ensures that block 54 is clamped in a position where the central axis of block 54 extends perpendicular to lower planar surface 50 .

[0095] The present invention also includes a method for elemental analysis of the sample under study 2 by optical emission spectroscopy on a laser-produced plasma.

[0096] The method includes the steps of preparing a sample 2 and then positioning the sample 2 on a stand 1 for its analysis.

[0097] In particular, the step of preparing the sample 2 includes forming the sample 2.

[0098] As shown schematically in FIGS. 2 and 3, the sample 2 has an essentially axisymmetric cylindrical shape.

[0099] For analytical purposes, the material to be analyzed corresponds, for example, to a metal strip contained in a resin block designed so that the strip to be analyzed is flush with one of the bases of the resin block, which block forms the sample 2 to be studied.

[0100] During the step of preparing the sample 2, a sub-step is carried out in which the sample 2 is ground to form a flat surface to be considered.

[0101] For this purpose, the resin block is ground by bringing its base, flush with the strip of material to be analyzed, into contact with the grinding surface.

[0102] Next, the step of positioning the sample 2 on the stand 1 for its analysis involves the use of the sample holder 5 previously described.

[0103] Therefore, this positioning step is - inserting the sample 2 into the sample holder 5, in particular inserting the sample 2 into the cavity 51 of the block 54 and positioning the flat surface to be considered against the bearing surface 520 of the sample holder 5; - adding elastic return means 53 pressing the flat surface under consideration of sample 2 against the bearing surface 520; Includes:

[0104] Then, of course, the stopper 57 is screwed in to allow the elastic return means to abut against this stopper 57 and exert an elastic return force on the sample 2 to maintain the sample 2 pressed against it.

[0105] The block 54 is then positioned on the base 55 and clamped by the holding means 56 .

[0106] Next, the laser-produced plasma can be analyzed by optical emission spectroscopy, with the sample holder 5 ensuring that the surface of the sample 2 to be analyzed is properly positioned perpendicular to the laser beam 30 and that the surface condition of the sample 2 to be analyzed does not have any height differences that lie outside the depth of field of the focus of the generation system 3.

Claims

1. 1. An analytical device for elemental analysis of a sample under study, comprising: a stand (1) having a flat surface (10) and intended to support a sample (2) to be studied; a system (3) for generating a laser beam (30) intended to generate a plasma (P) that impinges on the sample under study (2) according to a direction perpendicular to the flat surface (10) of the stand (1) and generates an optical emission (40); means (4) for collecting said emitted light (40); Equipped with The analytical device comprises a sample holder (5), which comprises: a lower flat surface (50) intended to rest on the flat surface (10) of the stand (1); a cavity (51) intended to receive said sample (2); at least one shoulder (52) forming a bearing surface (520) directed towards the cavity (51), said bearing surface (520) being inscribed in a plane parallel to the lower flat surface (50) of the sample holder (5); elastic return means (53) configured to press the sample (2) against the bearing surface (520); a cylindrical block (54) having said cavity (51) and said at least one shoulder (52); a base (55) having said lower flat surface (50) and holding means (56) for holding said block (54) on said base (55), said holding means (56) comprising two jaws (561) for clamping said block (54), each having a clamping surface (562) whose generatrices extend perpendicular to said lower flat surface (50); An apparatus comprising:

2. 2. The device according to claim 1, wherein said cylindrical block (54) is axially symmetrical and cylindrical.

3. 3. The device of claim 2, wherein said shoulder (52) has an annular shape.

4. 4. Device according to any one of claims 1 to 3, characterized in that the sample holder (5) comprises a stop (57) connected to the block (54) and forming a support for the elastic return means (53).

5. 5. Device according to any one of claims 1 to 4, characterized in that the elastic return means (53) have at least two upper contacts (531) intended to come into contact with the sample (2) and at least two lower contacts (532) intended to abut against the stops (57).

6. A device according to any one of the preceding claims, characterized in that said elastic return means (53) have the form of a wave spring washer.

7. 7. Device according to claim 5 or 6, characterized in that the spring washer has an S-shaped profile in side view.

8. 1. A method for elemental analysis of a sample (2) under study by optical emission spectroscopy on a laser-produced plasma, comprising: preparing a sample (2) and positioning said sample (2) on a stand (1) for its analysis, The step of preparing the sample (2) includes a sub-step of grinding the sample (2) to form a flat surface to be examined; The positioning step includes the use of a sample holder (5), the sample holder (5) comprising: a lower flat surface (50) intended to rest on the flat surface (10) of said stand (1); a cavity (51) intended to receive said sample (2); at least one shoulder (52) forming a bearing surface (520) directed towards the cavity (51), said bearing surface (520) being inscribed in a plane parallel to the lower flat surface (50) of the sample holder (5); elastic return means (53) configured to press the sample (2) against the bearing surface (520); a cylindrical block (54) having said cavity (51) and said at least one shoulder (52); a base (55) having said lower flat surface (50) and means (56) for holding said block (54) on said base (55), said holding means (56) comprising two jaws (561) for clamping said block (54), each having a clamping surface (562) whose generatrices extend perpendicular to said lower flat surface (50); The present invention is characterized by comprising: The positioning step includes: the sub-steps of inserting the sample (2) into the sample holder (5) and positioning the planar surface under consideration on the bearing surface (520) of the sample holder (5) inscribed in a plane parallel to the lower planar surface (50) of the sample holder (5) intended to rest on the planar surface (10) of the stand (1); adding the elastic return means (53) for pressing the planar surface under consideration of the sample (2) against the bearing surface (520); A method comprising:

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