Apparatus for analyzing a metal sample using a laser beam, comprising means for shaping the laser beam - Patent 7222247

Abstract

The present invention relates to a diaphragm 7 of an elemental analysis device 3, comprising a body 71 provided with a selective opening 72 for selecting a portion of a laser beam 5, characterized in that the diaphragm 7 is impermeable to the waves of the laser beam and holds an element 73 positioned within the selective opening 72 for deforming the selective opening 72 into an annular shape.

Description

[Technical Field]

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

[0002] More particularly, the present invention relates to high resolution analytical instruments, particularly but not exclusively for mapping elements within metallic solids.

[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 hydrides, 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] Conventionally, analytical devices have - a module for generating a laser beam; a diaphragm for selecting a portion of the laser beam emitted by the generating module; - optical means for focusing the laser beam onto the sample under study; - means for collecting luminescence; - a means for determining the elements of the sample under consideration; The device has a frame to which the

[0012] Once generated by the generating module, the laser beam travels until it reaches the sample under consideration.

[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 optical emission is performed by a collecting means, which is then analyzed by a determining means to map the elements that make up the sample under consideration.

[0015] However, the interaction between the laser and the sample material under study is directly related to the geometry of the plasma and the aperture of the focused beam.

[0016] The focused beam is the portion of the laser beam that is located between the last lens and the sample.

[0017] This focused beam has a conical shape that tapers from the last lens.

[0018] In analytical situations, the larger the aperture of the focused beam, the less of the beam that is absorbed by the plasma, which benefits the ablation of the surface of the sample by the laser beam and therefore the quality of the analysis.

[0019] In other words, the larger the cone is at its base, the better the interaction between the beam and the sample material, and consequently the better the analytical results.

[0020] On the other hand, the smaller the aperture of the focused beam, the more of the beam is absorbed by the plasma, which is detrimental to the ablation of the surface of the sample by the laser beam and, consequently, to the quality of the analysis.

[0021] In other words, the smaller the cone is at its base, the worse the interaction between the beam and the sample material, and consequently the worse the results of the analysis.

[0022] However, increasing the aperture of the focused beam results in a central cone with a small aperture that becomes increasingly larger depending on the aperture of the focused beam.

[0023] The presence of this central cone with a small opening then leads to a decrease in the quality of the analysis as explained above. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] European Patent No. 0,654,663 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 invention is to provide a solution that allows the generation of a beam with a large aperture, which improves the quality of the analysis compared to prior art solutions.

[0027] Another object of the present invention is to provide such a solution that is compatible with focused beams of all sizes.

[0028] A further object of the present invention is to provide such a solution that is simple to implement. [Means for solving the problem]

[0029] These objectives, and others that will become apparent later, - a module for generating a laser beam; - optical means for focusing the laser beam onto the sample under study; - means for collecting luminescence; - a means for determining the elements of the sample under consideration; 1. An apparatus for the elemental analysis of a sample under consideration, comprising a frame on which are mounted: This is achieved by the present invention relating to the analytical device, which is characterized in that the analytical device also comprises a module for shaping a laser beam incorporating at least one lens and a diaphragm for selecting a portion of the laser beam emitted by the generation module, the diaphragm having a body provided with an opening for selecting a portion of the laser beam, and the diaphragm holds an element that is positioned within the selective opening and deforms the selective opening into an annular shape, and through which the waves of the laser beam cannot pass.

[0030] The use of such a diaphragm makes it possible to obtain at the output of the focusing means focused laser radiation that does not have a central cone with a small aperture.

[0031] This in turn has a direct benefit to the quality of the ablation of the sample by the laser radiation, thereby facilitating the use of the ablation results to map the elements that make up said sample.

[0032] In fact, the diaphragm makes it possible to mask the central part of the laser beam, so that it does not have a central cone that would degrade the quality of the laser beam when it is intended to be an open beam at the output of the focusing optics.

[0033] According to an advantageous embodiment, the non-penetrable element has a shape complementary to the shape of the selective opening.

[0034] Such shape complementarity makes it possible to obtain a tubular shaped laser beam whose outer contour of the masked cross section corresponds to the outer contour of the selected opening in the diaphragm.

[0035] This allows the uniformity of the laser beam to be maintained, and when the laser beam is used to ablate a sample, it allows the uniform shape of the ablation to be maintained, making it easier for a technician to analyze the ablation.

[0036] According to another advantageous aspect, the impermeable element is connected to the body by at least one retaining arm.

[0037] This makes it possible to maintain the position of the impermeable element in all circumstances, especially when the diaphragm is moved from one position to another.

[0038] In other words, when the diaphragm is moved, the non-permeable element does not need to be repositioned relative to the selected opening, only the position of the diaphragm relative to the laser production module is adjusted.

[0039] According to another advantageous aspect, the impermeable element is made integral with the body.

[0040] In this case, the diaphragm can be made, for example, by material extrusion, stock cutting (ie machining a blank or cut piece of material).

[0041] Furthermore, this ensures that the non-permeable element maintains its position relative to the selection opening.

[0042] According to another advantageous aspect, the impermeable element is fixed to the film.

[0043] By positioning the non-permeable element on the film, it becomes possible to vary the shape and / or size of the non-permeable element, in fact, in that case all that is required to change the shape of the beam coming from the diaphragm as required is to change the film.

[0044] According to another advantageous aspect, the film is transparent to the wave of the laser beam for which the diaphragm is selected.

[0045] In this way, the film does not impede the passage of the laser radiation, which limits the risk of degradation of the quality of the laser radiation.

[0046] Furthermore, the present invention provides - generating a laser beam via a generation module; - focusing the laser beam via focusing optical means to obtain a focused beam; - determining the elemental composition of the sample under consideration via a collecting means and a determining means; A method for elemental analysis of a sample under consideration by means of an analytical device as described above, comprising: The method relates to a method in which the step of focusing the laser beam includes the substep of masking a central cone in the focused beam via a diaphragm.

[0047] In this way it is guaranteed that a focused beam is obtained that does not have a central cone with a small aperture, ie the beam coming from the focusing means.

[0048] Other characteristics and advantages of the invention will become more apparent on reading the following description of a preferred embodiment of the invention, given as an illustrative and non-limiting example, and also from the accompanying drawings, which are described below. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a schematic diagram of an analytical system including an analytical device according to the present invention; [Figure 2] 3 is a schematic detail of a focused beam obtained by the focusing optical means of the analysis device according to the invention; FIG. [Figure 3] 1 is a schematic perspective view of a diaphragm of an analytical device according to the present invention, according to a first embodiment; [Figure 4] 1 is a schematic perspective view of a diaphragm of an analytical device according to the invention, according to a second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0050] FIG. 1 shows a system 1 for elemental analysis of a sample 2 under consideration.

[0051] The system 1 includes an analytical device 3, which will be described below. The analytical device 3 comprises a stand 31 for receiving a sample 2.

[0052] The analysis device 3 also a module 4 for generating a laser beam 5; a module for shaping the laser beam 5 incorporating at least one lens 6 and a diaphragm 7 for selecting a portion of the laser beam 5 emitted by the generation module 4; optical means 8 for focusing the laser beam 5 onto the sample 2 under study; It also has a frame on which it is attached.

[0053] As shown by FIG. 1, the analysis device 3 comprises a number of lenses 6 and diaphragms 7 along the direction of emission of the laser beam 5 from the generation module 4 towards the sample 2 .

[0054] The analysis device 3 also comprises a number of mirrors 32 making it possible to deflect the laser beam 5 from the generation module 4 until it reaches the focusing means 8 in order to limit the footprint of the analysis device 3 .

[0055] At the output of the focusing optical means 8, the laser beam 5 becomes a focused beam 51. In this case, the focused beam 51 has a conical shape that tapers in the direction of the sample 2, whereas between the generating module 4 and the focusing means 8 the laser beam 5 has a substantially cylindrical shape.

[0056] Furthermore, the system 1 comprises collecting means 9 and determining means 10. The role of these means will be explained below.

[0057] As previously mentioned, the system 1 allows for the analysis of a sample 2 to map its elemental composition.

[0058] For this purpose, a laser beam 5 is emitted by the generation module 4 so as to be directed towards the sample 2 and to impinge on its surface.

[0059] When the laser beam 5 strikes the sample 2 under consideration, a plasma P is generated, producing an optical emission that is analyzed to map the elements that make up the sample 2 .

[0060] Collection of the plasma emission is performed by collection means 9 .

[0061] For this purpose, as shown by FIGS. 2 and 3, the collecting means 9 comprise an optical fiber 91 whose free end, which defines the termination, is closest to the plasma P.

[0062] The collecting means 9 also comprise first communication means 95 intended to establish a communication path with the second communication means 101 of the determining means 10 .

[0063] The first communication means 95 and the second communication means 101 may be of the wireless type, or they may be in the form of connectors intended to receive plugs of wired connection cables.

[0064] The focused beam 51 can have a large aperture or a small aperture.

[0065] More specifically, the focused beam 51 has a conical shape that tapers from the last lens, i.e., the focusing optics 8. As shown in FIG. 2, the focused beam 51 has a truncated conical shape between the focusing optics 8 and the sample 2. This truncated conical shape results from the sample 2 being positioned a predetermined distance from the focusing optics 8 such that the cross section of the focused beam 51 is larger than the simple point formed by the ends of the cone shape of the focused beam. In other words, the distance between the focusing optics 8 and the sample 2 is strictly less than the height of the cone formed by the focused beam 51. It should be recalled that the height of the cone is measured from the base to the apex of the cone.

[0066] In analytical situations, the larger the aperture of the focused beam 51, the less the beam 5 is absorbed by the plasma P, which is beneficial for the ablation of the surface of the sample 2 by the laser beam 5 and therefore also for the quality of the analysis.

[0067] In other words, the larger the cone is at its base, the better the interaction between the beam 5 and the material of the sample 2 and therefore the better the results of the analysis.

[0068] On the other hand, the smaller the aperture of the focused beam 51, the more of it will be absorbed by the plasma P, which is detrimental to the ablation of the surface of the sample 2 by the laser beam 5 and therefore to the quality of the analysis.

[0069] In other words, the smaller the cone is at its base, the worse the interaction between the beam 5 and the material of the sample 2, and consequently the worse the results of the analysis.

[0070] However, as shown in FIG. 2, increasing the aperture of the focused beam 51 results in a central cone 52 with a small aperture that becomes increasingly larger depending on the aperture of the focused beam 51.

[0071] The presence of this central cone 52 with a small opening reduces the quality of the analysis as explained above.

[0072] The diaphragm 7 of the module shaping the laser beam 5 is specifically designed to eliminate or at least limit this central cone 52 .

[0073] More specifically, with reference to Figures 3 and 4, the diaphragm 7 comprises a body 71 having a selective opening 72 therein.

[0074] When the laser beam 5 passes through the diaphragm 7, a portion of its cross section is blocked by the body 71 of the diaphragm 7 so that only the portion located opposite the selective opening 72 can pass through the diaphragm 7.

[0075] Furthermore, the diaphragm 7 carries an element 73 through which the waves of the laser beam 5 cannot pass.

[0076] The impermeable element 73 is positioned within the selected opening 72 as shown in FIGS.

[0077] The non-transmissive element 73 then forms a barrier to the wave of the laser beam 5, thereby deforming the selective opening 72 into an annular shape.

[0078] The laser beam 5 emerging from the diaphragm 7 then has a tubular shape as opposed to the solid cylindrical shape it had before reaching the diaphragm 7 .

[0079] In Figures 3 and 4, the body 71 of the diaphragm 7 has a length substantially equal to its width (or its diameter, since a body having a circular cross section is shown here) and is therefore substantially cylindrical, or the diaphragm 7 may have a shorter length so as to assume a substantially annular shape.

[0080] According to a first embodiment illustrated by FIG. 3, the impermeable element 73 is connected to the body 71 via at least one retaining arm 74 .

[0081] According to the particular embodiment of Figure 3, the diaphragm 7 comprises three equally spaced arms 74. More specifically, each arm 74 is spaced apart from the other arms 74 by an angle of 120 degrees.

[0082] The arms 74 and the impermeable element 73 can be made integral with the body 71. In other words, the arms 74 and the impermeable element 73 are made from the same material as the body 71, just as the diaphragm 7 is obtained, for example, by machining or cutting a block of material or directly from a casting.

[0083] According to other variants, the diaphragm may comprise only two arms 74 or, conversely, four or more arms 74 .

[0084] According to a second embodiment illustrated by FIG. 4, the impermeable element 73 is fixed to a film 75 .

[0085] The film 75 is then applied to the body 71 of the diaphragm 7 and is held to the body 71 by ad hoc means.

[0086] Advantageously, the film 75 is transparent to the waves of the laser beam 5 .

[0087] In other words, the film 75 is transparent to the wave of the laser beam 5 for which the diaphragm 7 is selected.

[0088] Alternatively, the film 75 may be independent of the body 71 of the diaphragm 7, for example by being attached to a support positioned in front of the body 71.

[0089] This makes it possible to maintain the full power and full spectrum of the laser beam 5 passing through the diaphragm 7 .

[0090] As described above, the analysis of the sample 2 by the analysis device 3 is performed as follows: - generating a laser beam 5 via a generation module 4; - focusing the laser beam 5 via optical means 8 to obtain a focused beam 51; - determining the elemental composition of the sample 2 under consideration via collecting means 9 and determining means 10; The method is carried out by a method including:

[0091] According to the invention, the step of focusing the laser beam 5 includes the sub-step of masking a central cone 52 in the focused beam 51 via a diaphragm 7 .

[0092] Masking of the central cone 52 is accomplished by the impermeable element 73 as previously described.

Claims

1. An analytical device (3) for elemental analysis of a sample (2) under study, comprising: a module (4) for generating a laser beam (5); optical means (8) for focusing said laser beam (5) onto the sample (2) under study; means (9) for collecting said emitted light; means (10) for elemental determination of the sample (2) under consideration; a frame having a The analysis device (3) also comprises a module for shaping the laser beam (5), the module incorporating at least one lens (6) and a diaphragm (7) for selecting a portion of the laser beam (5) emitted by the generation module (4), the diaphragm (7) comprising a body (71) provided with an opening (72) for selecting a portion of the laser beam (5), the diaphragm (7) being coupled to an element (73) positioned within the selection opening (72) and deforming the selection opening (72) into an annular shape, through which the waves of the laser beam (5) cannot pass.

2. 2. An analytical device (3) according to claim 1, characterized in that the non-permeable element (73) has a shape complementary to the shape of the selective opening (72).

3. 3. An analytical device (3) according to claim 1 or 2, characterized in that the non-permeable element (73) is connected to the body (71) by at least one retaining arm (74).

4. 4. An analytical device (3) according to claim 3, characterized in that the non-penetrable element (73) is made integral with the body (71).

5. 3. An analytical device (3) according to claim 1 or 2, characterized in that the non-permeable element (73) is fixed to a film (75).

6. 6. The analytical device (3) according to claim 5, characterized in that the film (75) is transparent to the wave of the laser beam (5) from which the diaphragm (7) is selected.

7. generating a laser beam (5) via said generating module (4); focusing said laser beam (5) via said focusing optical means (8) to obtain a focused beam (51); determining the elemental composition of the sample under study (2) via said collecting means (9) and said determining means (10); A method for elemental analysis of a sample (2) under consideration by an analysis device (3) according to any one of claims 1 to 6, comprising: A method, wherein the step of focusing the laser beam (5) comprises the sub-step of masking a central cone (52) in the focused beam (51) via the diaphragm (7).

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