Interchangeable spark unit, system and calibration method

Abstract

The present invention relates to an exchangeable spark unit for an optical emission spectrometer, a system for analyzing samples using optical emission spectroscopy, and a method for calibrating an exchangeable spark unit. The exchangeable spark unit (10) for an optical emission spectrometer (12) comprises a sample carrier (20) defining a sample plane (22) for positioning a sample to be analyzed, the sample carrier (20) having an aperture (24), and an electrode (26) arranged at a distance (D) relative to the sample plane (22) in the region of the aperture (24) such that a spark can be generated between the electrode (26) and a sample positioned in the sample plane (22) to emit light. The exchangeable spark unit (10) further comprises a coupling interface (30) for mechanically coupling the exchangeable spark unit (10) with the optical emission spectrometer (12) and an optical component (44) for influencing the emitted light.

Description

[Technical field]

[0001] The present invention relates to a replaceable spark unit for an optical emission spectroscopy instrument, a system for analyzing a sample using optical emission spectroscopy, and a method for calibrating the replaceable spark unit. [Background technology]

[0002] During different stages of metallurgical steel processing, e.g. converter processing, samples are taken from the molten steel and analyzed to determine the chemical composition. This makes it possible to control the process stages and adjust the properties of the steel produced. Typically, spark emission spectroscopy (OES) is used to determine the chemical composition of a steel sample. In this method, electrical energy is used to generate a spark between a solid steel sample and an electrode, as described for example in US Pat. No. 5,285,251. Through this, the atoms or ions of the sample are excited, creating a discharge plasma with a unique emission spectrum for each chemical element. Optical processing and analysis of the spectral lines of this spectrum makes it possible to determine the presence of the chemical elements present. By using a suitably calibrated system, the amount of the sample can be determined, and therefore also the chemical composition. Such methods are disclosed in US Pat. No. 4,592,655 (A), US Pat. No. 7,911,606 (B2) and German Patent No. 3,344,944 (A1).

[0003] In early methods, samples were mechanically prepared by cooling and grinding. In addition, the analysis was performed spatially away from the sampling site, i.e., the steel plant. Thus, there was a long turnaround time between sampling and receiving the results. Devices and methods have been developed to accelerate this process.

[0004] Eliminating the need for surface preparation reduces analysis time and is also economically advantageous for metal producers. Various solutions to this problem are described in European Patents 3336511(A1), 3336512(A1), 3336513(A1), 3336514(A1), 3581913(A1), and 3581914(A1). These documents relate to Direct Analysis (DA) samplers, a type of molten metal immersion sampler that produces DA samples. DA samples do not require any type of surface preparation before analysis, and therefore the use of spark-OES analysis can provide significant economic benefits in terms of both the availability of timely chemical results as well as laboratory time savings.

[0005] During spark OES, particles detached from the sample by the spark cause contamination of the spark chamber and adjacent areas of the spectroscopic analysis device. Such particles may accumulate on optical elements such as windows, mirrors, lenses, or detectors and must be removed to ensure consistent quality of the analysis. Since such cleaning is time consuming, OES systems with replaceable spark units have been provided. Thus, the spark unit can be replaced after one or more measurements to be ready for the next analysis within a few minutes. Such systems are disclosed in WO 2021 / 048382 (A2) and GB 2592853 (A), which are from the same family, as well as in US 2021 / 0285820 (A1). A handheld device for spectroscopic analysis is known from US Pat. No. 4,411,524 (A). Summary of the Invention [Problem to be solved by the invention]

[0006] However, known spectroscopic analysis devices must be calibrated or recalibrated after replacement of the spark unit in order to obtain reliable results. Due to the nature of the analysis, even small deviations from the desired values ​​lead to significant differences in the analyzed light and therefore in the analysis results. For example, small deviations from the desired distance between the electrode and the sample, or between the spark and the optical components for processing the emitted light, lead to a significant reduction in the light intensity and, if applicable, a change in the light composition. Different deviations can accumulate. However, replacement and recalibration of the spark unit is time-consuming and labor-intensive.

[0007] The problem to be solved is to provide a spark unit, system, and calibration method that allows for fast and easy replacement of the spark unit. [Means for solving the problem]

[0008] The problem is solved by a replaceable spark unit according to claim 1 and by a system and method according to the additional claims. Embodiments arise from the dependent claims.

[0009] An exchangeable spark unit for an optical emission spectrometry device serves to solve the problem. The exchangeable spark unit comprises a sample carrier defining a sample plane for positioning a sample to be analyzed. The sample carrier has an aperture. The exchangeable spark unit comprises an electrode, which is arranged at a distance relative to the sample plane in the area of ​​the aperture, such that a spark can be generated between the electrode and a sample positioned in the sample plane in order to emit light. The exchangeable spark unit further comprises a coupling interface for mechanically coupling the exchangeable spark unit with the optical emission spectrometry device and an optical component for influencing the emitted light.

[0010] Preferably, the electrodes and optical components are contained within the same compartment of the replaceable spark unit, i.e., the electrodes and optical components are located in a single compartment of the replaceable spark unit. Thus, these components can be replaced together, facilitating replacement of the spark unit. Additionally, the replaceable spark unit can be calibrated prior to installation and / or replacement.

[0011] In particular, the sample carrier, the electrodes and the coupling interface of the replaceable spark unit are made of metal. In particular, the electrodes are made of tungsten. The electrodes can be electrically insulated from the sample carrier.

[0012] The replaceable spark unit according to the invention comprises optical components that affect the light before it enters the optical emission spectrometer. Thus, part of the optical effects and processes required to analyze the optical spectrum of the spectrometer to determine the composition of the sample are already performed in the replaceable spark unit. When replacing the spark unit, the optical path between the spark position and the optical components is not affected. This optical path can be precisely adjusted in the replaceable spark unit. The replaceable spark unit according to the invention therefore makes it possible to fixedly define in the spark unit part of the path traveled by the light between the spark and the spectrometer. It is therefore possible to replace a contaminated replaceable spark unit with a new one that is already calibrated and defines exactly the same optical path. Most of the optical path is not affected by replacing the spark unit. Therefore, after replacing the spark unit according to the invention, it is not necessary to recalibrate the entire instrument.

[0013] Specifically, the replaceable spark unit and optical emission spectrometer serves to analyze samples during the steelmaking process in a steel plant close to the converter. The device must therefore function reliably under harsh conditions, including heat and contamination. A fast and easy replacement of the replaceable spark unit is therefore required. In addition, in this environment, samples must be analyzed regularly at time intervals of 30-45 minutes. For this reason, replacement of the spark unit must be completed in less than 20 minutes. This is possible with the replaceable spark unit according to the invention, since no recalibration is necessary. Long-term operation of the spectrometer can be achieved by regular replacement of the spark unit.

[0014] The spark unit is a device capable of generating sparks in order to analyze a sample. The sparks are generated by electrical energy applied, in particular, between the sample and the electrode. The sample carrier is a component capable of positioning the sample for analysis. The aperture is an aperture of the sample carrier, which is arranged in the sample plane and passes completely through the sample carrier, so that there is a free space between the sample placed on the sample carrier and the electrode, in particular the electrode tip. Thus, a spark can be generated in the free space. The distance between the electrode and the sample plane is in particular between 1 mm and 4 mm, more particularly between 1.5 mm and 2.5 mm, and preferably about 2 mm.

[0015] The electrode is arranged in the aperture area. This allows for spark generation between the electrode and the sample positioned in the sample plane. In particular, the electrode is arranged coaxially with the aperture. The electrode may have a cylindrical and / or conical shape. Preferably, the electrode has an electrode body and an electrode tip, the diameter of the electrode tip being smaller than the diameter of the electrode body. The electrode tip may be pointed and / or sharp to ensure a stable spark position. The electrode body may be essentially cylindrical, in particular cylindrical. The electrode may have an electrode head with an electrode tip, the electrode head being pyramidal and / or pointed. In one configuration, the electrode is arranged essentially vertically. In particular, the electrode is generally elongated and / or pin-shaped. The aperture may have a circular cross section. The central axis of the electrode may pass through the aperture, in particular through the center of the aperture. The claimed design prevents spark generation between the sample carrier and the electrode. Additionally, an insulating element may be provided between the electrode and the housing of the replaceable spark unit for electrical insulation.

[0016] In a preferred configuration, the sample plane is horizontal. The sample can thus be conveniently positioned and, if applicable, fixed. Preferably, the sample carrier has a flat surface that defines the sample plane. The sample plane, in particular the flat surface, may form the upper surface of the replaceable spark unit. The sample is in particular a metal sample.

[0017] The spark causes the emission of light that is characteristic of the composition of the sample. The replaceable spark unit is coupled to an optical emission spectrometer for analyzing the emitted light. In the following, the optical emission spectrometer is referred to as the spectrometer. The spark unit is replaceable such that it can be mechanically decoupled from the spectrometer and another spark unit according to the invention can be mechanically coupled to the spectrometer.

[0018] The coupling interface contacts the spectroscopic analyzer and thus defines the position of the replaceable spark unit relative to the spectroscopic analyzer. Typically, the coupling interface defines at least the height position (height or z-position) of the replaceable spark unit. In particular, the spectroscopic analyzer and the replaceable spark unit cannot move relative to each other in the coupled state, at least when no external force is applied. The coupling interface may comprise one or more surfaces that can be positioned adjacent to corresponding surfaces of the spectroscopic analyzer. In particular, the replaceable spark unit can be coupled to a housing of the spectroscopic analyzer, in which the components for optical detection are enclosed. The coupling interface may define a coupling plane. The coupling plane may be a bottom surface of the replaceable spark unit. This allows a particularly convenient and error-free installation of the replaceable spark unit.

[0019] Specifically, the replaceable spark unit includes an optical outlet, which is an outlet through which light affected by the optical components can exit the spark unit to enter a spectroscopic instrument for analysis.

[0020] An optical component is a component that affects or changes at least one property of the incident light. An optical component may be, among others, a lens, a mirror, a filter, a beam splitter, a prism, an optical slit, or a diffraction grating. Thus, one or more of the intensity, direction, focus, dispersion, composition, and / or further properties of the incident light can be affected. Gaseous media or optical fibers are not optical components according to the present invention. In particular, the optical components of the replaceable spark unit do not attenuate the light by more than 10%.

[0021] In one embodiment, the replaceable spark unit comprises a first hollow space for light to pass from the generated spark to the optical component and a second hollow space for light to pass from the optical component towards the light outlet of the replaceable spark unit. The compartment containing the electrodes and optical components of the replaceable spark unit comprises the first and second hollow spaces, i.e. the first and second hollow spaces form at least a part of the volume of the compartment. In particular, the angle α between the longitudinal extension of the first hollow space and the longitudinal extension of the second hollow space is between 45° and 120°, more particularly between 90° and 110°.

[0022] The hollow space serves to transmit light. Typically, the first and / or second hollow space have a generally cylindrical shape and / or are realized as tubes. The angle α is measured along the central longitudinal axis of the respective hollow space, which may define a centerline through which the light passes. Below 45°, the hollow space is positioned far away from the electrode, which requires a very large construction space. In particular, the angle is greater than 90° in order to ensure that the sample plane does not include any obstructing components. Between 90° and 110°, an optimal use of the space is possible. In one configuration, the angle α is about 100°. In particular, the second hollow space is at least essentially vertical.

[0023] In one embodiment, the replaceable spark unit comprises a mirror as an optical component. In particular, the optical component is a mirror for reflecting the emitted light. Thus, the light can be directed along a predefined path and / or towards one or more further optical components so that the emitted light can be analyzed by a spectroscopic analyzer. This embodiment allows for a compact construction since the light can be directed towards a spectroscopic analyzer close to the electrode.

[0024] In one embodiment, the replaceable spark unit includes a first hollow space for light to pass from the generated spark to the mirror and a second hollow space for light to pass from the mirror to the light outlet of the replaceable spark unit. Specifically, the angle α between the longitudinal extension of the first hollow space and the longitudinal extension of the second hollow space is between 45° and 120°, more specifically between 90° and 110°.

[0025] In one embodiment, the mirror is configured to reflect the incident light with an angle β of 5°-20°, preferably 8°-12°, relative to the sample plane. If the angle is smaller, the sample plane is blocked by the mirror. If the angle is larger, the spark cannot be fully represented by the emitted light. In addition, blackbody radiation from the hot sample spark region will then enter the spectroscopic analyzer, which leads to an increase in stray light levels. That is, β may be preferably about 10°.

[0026] In one embodiment, the mirror is arranged such that the light reflected by the mirror travels essentially vertically downwards. The sample plane is typically aligned horizontally. Thus, the light reflected by the mirror typically travels perpendicular to the sample plane. This allows for a particularly small construction space.

[0027] In one embodiment, the replaceable spark unit includes a window to allow light to pass toward the optical emission spectroscopy instrument while closing a hollow space for the light to pass through the replaceable spark unit.

[0028] The window acts as an optical outlet for the light affected by the optical component. The closing contributes to keeping the inert gas inside the respective hollow space. In particular, the window allows the light to pass from the second hollow space to the optical emission spectrometer while closing the second hollow space. To contribute to closing the second hollow space, an O-ring can be placed, for example, around a further optical component, for example a filter.

[0029] In one embodiment, the window is configured as an optical component. In particular, the window is configured as a filter or as a lens that allows only a portion of the incident light to pass to the optical emission spectrometer. In other words, the filter reduces the light intensity. Thus, the overall light intensity can be adapted to an amount suitable for the analysis of the spectrometer. The filter can be a neutral density filter. Preferably, the filter is configured to pass less than 50% of the incident light, more preferably less than 30%. In one configuration, the filter attenuates the light intensity by a factor of 10. In one configuration, an additional optical component can be placed in the replaceable spark unit. The additional optical component can be a lens or a filter. Thus, the filter can be placed on top of the lens that acts as a window.

[0030] In one embodiment, the electrode comprises a bearing surface and the replaceable spark unit comprises a positioning element for positioning the bearing surface of the replaceable spark unit such that the distance between the electrode and the sample plane is determined by the positioning element.

[0031] The bearing surface is typically positioned relative to at least one other part of the replaceable spark unit fixed in place in the sample plane, in other words the positioning element serves inter alia to define the distance between the electrode and the at least one other part of the replaceable spark unit.

[0032] By adjusting / selecting the height of the positioning element, the distance D between the electrode and the sample plane can be adjusted. In this way, the distance D can be set particularly accurately. In particular, the positioning element can be selected before coupling the exchangeable spark unit to the spectroscopic device in order to obtain a constant distance D. In particular, the electrode can be adjusted in height by rotating it like a screw. It can thus be ensured that said distance D is accurate, which allows in particular accurate measurements after exchanging the spark unit without recalibration. In one configuration, the electrode can be fixed in the mounted state.

[0033] The positioning element may be, for example, a precision washer fitted so as to be precisely measured to adjust the distance D in question.

[0034] In one embodiment, the replaceable spark unit includes a gas inlet disposed in the second hollow space. Thus, the second hollow space, and subsequently also the first hollow space, can be filled with an inert gas that is heavier than air, such as argon. Specifically, the gas inlet is positioned at a low position in the second hollow space.

[0035] In one embodiment, the replaceable spark unit includes a gas outlet disposed in a third hollow space through which the electrode extends. This allows a downward flow of an inert gas, such as argon, from the electrode tip to the gas outlet. The third hollow space may be essentially cylindrical, at least in cross section. At least a portion of the electrode is disposed within the third hollow space. Specifically, the gas outlet is disposed at a lower position than the electrode tip. Thus, gravity can support the transport of the ablated material to the gas outlet.

[0036] In one embodiment, the replaceable spark unit comprises a fastening means for mechanically fastening the replaceable spark unit to the optical emission spectroscopy device in a mechanically coupled state. Specifically, the fastening means comprises one or more screws. In other words, the replaceable spark unit can be mechanically fastened to the optical emission spectroscopy device in a coupled state. Specifically, all degrees of freedom are constrained such that a stable connection of the replaceable spark unit and the optical emission spectroscopy device is achieved.

[0037] In one embodiment, the replaceable spark unit comprises a positioning pin for positioning the replaceable spark unit relative to the optical emission spectrometer, or a receiving space for receiving the positioning pin. The positioning pin can be attached to the replaceable spark unit or the optical emission spectrometer. In that case, the respective other item comprises a receiving space for receiving the positioning pin. The positioning pin can also be a separate element arranged inside the receiving space of the replaceable spark unit and the receiving space of the spectrometer. In particular, the positioning pin is perpendicular to the lower surface of the replaceable spark unit and / or the upper surface of the optical emission spectrometer. The positioning pin defines the relative position at least along said surfaces.

[0038] In one embodiment, the replaceable spark unit comprises an orientation means for reaching a defined angular orientation between the replaceable spark unit and the spectroscopic analyzer when in a mechanically coupled state. The orientation means ensures correct positioning of the replaceable spark unit on the spectroscopic analyzer, specifically in at least two directions perpendicular to each other, which may be referred to as the x-direction and the y-direction. In one configuration, a positioning pin may be positioned off-center to serve as the orientation means. In other words, the positioning pin has an offset. It may be rotationally asymmetrically shaped. A suitable positioning pin may serve to position the replaceable spark unit both rotationally and translationally with respect to the spectroscopic analyzer. Alternatively or additionally, the orientation means may comprise a form element, such as at least a part of the outer contour of the component that interacts with a corresponding form element for positioning.

[0039] In one embodiment, the sample carrier is made of a conductive material and is provided with electrical contacts for applying an electrical potential through the sample carrier to a sample positioned on the sample carrier. In other words, the sample carrier contacts the sample and thus forms part of an open electrical circuit between the power supply, the electrodes and the sample, which is temporarily closed by a spark to analyze the sample. In one configuration, the sample plane is aligned essentially horizontally as intended during use.

[0040] In one configuration, the replaceable spark unit includes a housing. The sample plane can define a top surface of the housing. In one configuration, the coupling interface and the optical outlet of the replaceable spark unit can be disposed on a side of the lower housing.

[0041] The housing may be made of metal. In particular, the sample carrier, electrodes, coupling interface, and / or housing of the replaceable spark unit may be made of metal. The electrodes may be electrically insulated from the housing and the sample carrier.

[0042] In particular, the sample plane and the plane defined by the coupling interface are parallel to each other. Typically, the two planes are arranged horizontally. This allows for a convenient and error-free installation of the exchangeable spark unit on the spectroscopic analyzer and at the same time a convenient and error-free positioning of the sample on the sample interface.

[0043] A further aspect of the invention is a system for analyzing a sample using optical emission spectroscopy. The system comprises a replaceable spark unit according to the invention and an optical emission spectroscopy device. The optical emission spectroscopy device comprises a coupling interface to which the coupling interface of the replaceable spark unit can be mechanically coupled. The coupling interface of the optical emission spectroscopy device is typically located on a housing of the spectroscopic device, preferably forming a top surface of the spectroscopic device. All the above mentioned features, embodiments and advantages of the replaceable spark unit are also valid for the system and vice versa.

[0044] In one embodiment the system comprises a sample fixing means for fixing the sample to be analysed on the sample carrier.

[0045] The optical emission spectrometer can be, for example, a Czerny-Turner spectrometer. In this case, a grating that diffracts the incident light is placed between a first mirror (collimating mirror) and a second mirror (focusing mirror) to focus the incident light at different peaks (spectral maxima). The light can be directed through the grating to a location where the spectrum can be analyzed, for example to a CCD detector.

[0046] A further aspect of the invention is a method for calibrating a replaceable spark unit. The method comprises providing a replaceable spark unit according to the invention. The method further comprises detecting a distance D between the electrode and the sample plane and adjusting the mounting position of the electrode if the distance D deviates from a desired distance. The mounting position of the electrode is the position of the electrode inside the housing of the replaceable spark unit relative to said housing or another reference point of the replaceable spark unit. Detecting the distance can be done by calibration measurements and / or using an optical emission spectrometer. Providing an accurate distance D is important for the analysis. The calibration method therefore allows replacing the spark unit without the need to recalibrate the entire instrument.

[0047] Specifically, determining whether the distance has deviated from the desired distance is performed by comparing the detected distance with the desired distance, and if the difference exceeds or falls below a predetermined threshold, the distance is determined to have deviated from the desired distance. This means that the mounting position is adjusted only if the difference exceeds or falls below the threshold. In one configuration, the desired distance is 2 mm and / or the threshold is ±0.05 mm. In one configuration, the threshold is less than ±5% of the desired distance, preferably ±2.5% of the desired distance.

[0048] Specifically, adjusting the electrode placement position is Adjusting the height of the electrodes, in particular by twisting them; and fixing the height of the electrode by inserting a positioning element selected according to its height.

[0049] In one embodiment, the method further comprises detecting a height H of the replaceable spark unit and adjusting the height H of the replaceable spark unit if the height H deviates from a desired height. The height H is the height of a part or all of the replaceable spark unit. Specifically, the height is measured between the sample plane and the coupling interface, e.g., the lowest point of the coupling interface. The height H also affects the length of the optical path and therefore the analysis. Thus, this embodiment allows for high accuracy analysis.

[0050] Adjusting the height refers to any step that affects the measured height. Adjusting the height is in particular performed by machining, for example grinding. The machining is preferably performed on the sample carrier.

[0051] Similar to above, the height may be determined to deviate from the desired distance if the height exceeds or falls below a predetermined threshold.

[0052] In one configuration, the method further comprises mechanically coupling the replaceable spark unit to the optical emission spectroscopy device. In that case, the method can also be referred to as a method for preparing a system for analyzing a sample using optical emission spectroscopy. The coupling step and the steps of detecting and adjusting the distance can in principle be performed in any order. However, the steps of detecting and adjusting are preferably performed before the step of coupling, in particular before delivering the replaceable spark unit. The optional step of detecting the height is performed in particular before the step of coupling. Thus, replacement of the spark unit can be performed particularly quickly.

[0053] In one configuration, the replaceable spark unit comprises a mounting block, typically made of metal. The mounting block may directly or indirectly hold at least one of the different components, such as a sample carrier, an optical component, or an electrode. The mounting block may constitute at least one of the different components, such as a coupling interface. In one configuration, the mounting block is manufactured by machining on a CNC machine, specifically a multi-axis CNC mill, using only one single setup. In other words, a piece of metal is mounted on the machine, which is not released until the final mounting block is completed. Thus, particularly low tolerances regarding distances, lengths, and angles are possible, which are not possible with the use of conventional machining tools.

[0054] In the following, exemplary embodiments of the present invention will be described in detail with reference to the figures. The features of the exemplary implementations may be combined individually or in multiple combinations with the claimed subject matter, unless otherwise indicated. The scope of protection claimed is not limited to the exemplary implementations. [Brief description of the drawings]

[0055] The figure shows: [Figure 1] 1 is a cross-sectional view of a system according to the present invention; [Diagram 2] FIG. 2 is an enlarged detail of “A” in FIG. [Diagram 3] FIG. 1 is a perspective view of a system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] Fig. 1 shows a system 15 according to the invention. The system comprises an exchangeable spark unit 10 according to the invention, which is shown in the circle marked "A" above. The exchangeable spark unit 10 is mechanically coupled to an optical emission spectrometer 12, for example a Czerny-Turner spectrometer 13. For this purpose, the exchangeable spark unit 10 is provided on the underside with a coupling interface 30, which is realized as a horizontal surface, and the optical emission spectrometer 12 is provided on the upper side with a corresponding coupling interface 32, which is also realized as a horizontal surface. In the coupled state shown in Fig. 1, the coupling interfaces 30, 32 lie on top of each other.

[0057] The optical emission spectrometer 12 may comprise optical components such as optical slits, collimating mirrors, diffraction gratings, focusing mirrors, and / or detectors such as CCD detectors. These components, and in particular also further elements of the optical emission spectrometer 12, may be housed in a suitable housing, which may consist of one or more parts. The coupling interface 32 may be formed by the housing.

[0058] The replaceable spark unit 10 comprises a sample carrier 20 defining a sample plane 22 in which a sample to be analyzed can be positioned. The sample carrier 20 is formed by the upper wall of a housing 28 of the replaceable spark unit 10. The sample plane 22 corresponds to the upper surface of the replaceable spark unit 10. The sample carrier 20 is formed with an aperture 24. The replaceable spark unit 10 further comprises an electrode 26 arranged at a distance to the sample plane 22 below the center of the aperture 24. By applying a potential between the sample and the electrode 26, a spark can be generated between the electrode 26 and a metal sample positioned in the sample plane 22. As a result, light is emitted that is configured depending on the composition of the sample. The light travels downwards from the spark position through the replaceable spark unit 10 and through a window 47 to the optical emission spectrometer 12 for analysis.

[0059] FIG. 2 shows an enlarged view of detail "A" of FIG. 1. The view shows the centerline 29 of the light beam between the spark location and an optical component 44 that influences the emitted light, and which in the configuration shown here is a mirror 45. However, in alternative configurations where the light direction potentially deviates, the optical component can also be realized as, for example, a lens, a filter, or a prism. In the configuration shown, the centerline 29 forms an angle β of about 10° with respect to the sample plane 20. The light reflected by the mirror 45 travels vertically downwards towards the light outlet 46 through which it exits the replaceable spark unit 10 and subsequently enters the optical emission spectrometer.

[0060] The light passes from the spark location to a mirror 45 inside the first hollow space 41. The first hollow space 41 is configured for the most part as a cylindrical tube. The light reflected by the mirror 45 passes through the second hollow space 42, which is also configured for the most part as a cylindrical tube. The angle α between the longitudinal extension of the first hollow space 41 and the longitudinal extension of the second hollow space 42 is approximately 100°. The angle α can also be measured between the center line 29 of the first hollow space 41 and the center line 29′ of the second hollow space 42.

[0061] The light outlet 46 is realized as a window 47 closing the second hollow space 42 in a downward direction. The window 47 can be configured as a further optical component, namely a filter 48, which allows only a part of the incident light to pass through the optical emission spectrometer.

[0062] The gas inlet 55 is located near the bottom end of the second hollow space 42. The gas outlet is located at or near the bottom of the third hollow space 43 where the electrode 26 is located. In particular, an inert gas that is heavier than air, for example argon, can be introduced into the gas inlet 55 to gradually fill the second hollow space 42 from the bottom to the top. As more inert gas is introduced, the first hollow space 41 and then the third hollow space 43 also fill. A portion of the gas can exit the replaceable spark unit 10 through the aperture 24. Another portion of the gas can exit the replaceable spark unit 10 through the gas outlet 56. Typically, during an analysis, a continuous gas flow occurs. During sparking, a high volumetric flow can occur and / or between sparking, a low volumetric flow can occur. Thus, material ablated from the sample is prevented from entering the first hollow space 41 and the second hollow space 42, but is instead transported downwards to exit through the gas outlet 56.

[0063] The electrode 26 is essentially pen-shaped and vertically aligned. At the bottom, it comprises an electrical connection 2 for applying an electric potential between the electrode 26 and the sample. At the top, it comprises an electrode tip that is used to generate a spark with the sample. The distance D between the electrode tip and the sample plane 24, i.e. also between the electrode tip and the sample, may be 2.0 mm. The electrode 26 comprises a peripheral shoulder 51 forming a horizontally aligned bearing surface 50. The electrode 26 rests on a positioning element 52 that may be arranged on or around at least a part of the circumference of the electrode 26. The positioning element 52 thus defines the distance D. The positioning element 52 may be rotationally symmetric. The lower part of the electrode 26 is surrounded by an electrical insulator 2.

[0064] Specifically, the replaceable spark unit 10 is configured such that the positioning element 52 can be removed and replaced with another positioning element 52. The distance D can then be adjusted by replacing the positioning element 52. In this manner, the desired distance can be adjusted precisely, without the need to calibrate the system before measuring, even after replacing the replaceable spark unit 10.

[0065] The sample carrier 20 is made of metal and is provided with electrical contacts for applying an electrical potential to the sample via the sample carrier 20. The electrical contacts may be realised as spark pins made of tungsten, as shown in Figure 2.

[0066] In the configuration shown in FIG. 2, the housing 28 of the replaceable spark unit 10 includes a mounting block. The mounting block may hold or form the different components directly or indirectly. The mounting block forms the coupling interface 30 and the second hollow space 42, and also holds the mirror 45 and optionally the electrode 26. In addition to the mounting block, the housing 28 comprises a top part that includes the sample carrier 20 and at least a part of the first hollow space 41. The top part is a separate component that may be fixedly attached to the mounting block. An O-ring is arranged in the horizontal plane between the top part and the mounting block to seal the third hollow space 43 against the leakage of inert gas. The overall height H of the replaceable spark unit 10 may be adjusted by affecting the height of the top part. This may be done with the mounting block attached to the top part as shown, or with the top part separated from the mounting block.

[0067] When replacing the replaceable spark unit 10, the electrical connection 2 on the electrode 26 can be loosened. In particular, the cable of the electrical power supply can be removed and reinstalled on the replacement spark unit. The electrical connection 2 can be realized as a plug or socket for easy disconnection and connection.

[0068] The coupling interface 30 is formed by the bottom surface of the replaceable spark unit 10 to form a plane. The coupling interface 32 of the optical emission spectrometer 12 is formed accordingly. The receiving space 65 is disposed in the replaceable spark unit 10 to receive the positioning pin 64 to facilitate correct positioning of the replaceable spark unit 10 relative to the optical emission spectrometer.

[0069] 3 shows a perspective view of a system 15 comprising a replaceable spark unit 10 and an optical emission spectrometer 12. Shown are flange-like protrusions at the lower end of the replaceable spark unit 10 and the upper end of the optical emission spectrometer 12, which are secured together by fastening means 60, i.e., screws 62. A similar fastener is provided on the rear side. [Explanation of symbols]

[0070] 1 Electrical insulators 2 Electrical Connections 10 Replaceable Spark Unit 12 Optical emission spectrometer 13 Spectroscopic analyzer 15 System 20 Sample Carrier 22 Sample plane 24 Aperture 26 electrodes 28 Housing 29 Center line 29' center line D Distance H Height 30 Bonding Interface 32 Bonding Interface 41 First Hollow Space 42 Second Hollow Space 43 The Third Hollow Space 44 Optical components 45 Mirror 46 light outlet 47 Windows 48 Filters α angle β angle 50 Bearing surface 51 Shoulder 52 Positioning Elements 55 Gas inlet 56 Gas outlet 60 Fixing means 62 Screw 64 Locating pin 65 Receptive Space

Claims

1. A replaceable spark unit (10) for an optical emission spectrometry instrument (12), comprising: a sample carrier (20) defining a sample plane (22) for positioning a sample to be analyzed, said sample carrier (20) having an aperture (24); an electrode (26) arranged at a distance (D) relative to the sample plane (22) in the region of the aperture (24) so ​​that a spark can be generated between the electrode (26) and a sample positioned in the sample plane (22) to emit light; a coupling interface (30) for mechanically coupling the replaceable spark unit (10) to the optical emission spectrometry device (12); The replaceable spark unit (10), further comprising an optical component (44) for influencing the emitted light.

2. The replaceable spark unit (10) of claim 1, characterized in that the replaceable spark unit (10) comprises a mirror (45) as the optical component (44).

3. 3. The replaceable spark unit (10) of claim 2, characterized in that the replaceable spark unit (10) comprises a first hollow space (41) for the passage of light from the generated sparks to the mirror (45) and a second hollow space (42) for the passage of light from the mirror (45) towards a light outlet (46) of the replaceable spark unit (10), wherein an angle α between a longitudinal extension of the first hollow space (41) and a longitudinal extension of the second hollow space (42) is between 45° and 120°, in particular between 90° and 110°.

4. 4. The replaceable spark unit (10) of claim 2 or 3, characterized in that the mirror (45) is configured to reflect incident light having an angle β of 5° to 20° with respect to the sample plane (20) and / or the mirror (45) is arranged such that the light reflected by the mirror (45) travels essentially vertically downwards.

5. The replaceable spark unit (10) according to any one of claims 1 to 4, characterized in that the replaceable spark unit (10) comprises a window (47) for allowing light to pass towards the optical emission spectrometer (12) while closing a hollow space (41, 42) for light to pass through the replaceable spark unit (10).

6. 6. The replaceable spark unit (10) of claim 5, characterized in that the window (47) is configured as a further optical component, in particular as a filter (48) that allows only a portion of the incident light to pass through the optical emission spectrometer (12).

7. 7. The replaceable spark unit (10) of any one of claims 1 to 6, characterized in that the electrode (26) comprises a bearing surface (50) and the replaceable spark unit (10) comprises a positioning element (52) for positioning the bearing surface (50) of the replaceable spark unit (10) such that the distance (D) between the electrode (26) and the sample plane (22) is determined by the positioning element (52).

8. The replaceable spark unit (10) of any one of claims 3 to 7, characterized in that the replaceable spark unit (10) comprises a gas inlet (55) arranged in the second hollow space (42).

9. 9. The replaceable spark unit (10) of any one of claims 3 to 8, characterized in that the replaceable spark unit (10) comprises a gas outlet (56) arranged in a third hollow space (43) through which the electrode (26) extends.

10. The replaceable spark unit (10) according to any one of claims 1 to 9, characterized in that the replaceable spark unit (10) comprises fixing means (60), in particular one or more screws (62), for mechanically fixing the replaceable spark unit (10) to the optical emission spectrometer (12) in a mechanically coupled state, and / or the replaceable spark unit (10) comprises a positioning pin (64) for positioning the replaceable spark unit (10) relative to the optical emission spectrometer (12) or a receiving space (65) for receiving a positioning pin (64).

11. The replaceable spark unit (10) according to any one of claims 1 to 10, characterized in that the replaceable spark unit (10) comprises an orientation means for reaching a defined angular orientation between the replaceable spark unit (10) and the spectroscopic analysis device (12) when in a mechanically coupled state.

12. The replaceable spark unit (10) according to any one of claims 1 to 11, characterized in that the sample carrier (20) is made from an electrically conductive material and is provided with electrical contacts for applying an electric potential via the sample carrier (20) to the sample positioned on the sample carrier (20).

13. A system (15) for analyzing a sample using optical emission spectroscopy, the system (15) comprising a replaceable spark unit (10) according to any one of claims 1 to 12 and an optical emission spectroscopy device (12), in particular a Czerny-Turner spectrometer (13), the optical emission spectroscopy device (12) comprising a coupling interface (32) to which the coupling interface (30) of the replaceable spark unit (10) can be mechanically coupled.

14. A method for calibrating a replaceable spark unit (10), the method comprising: Providing a replaceable spark unit (10) according to any one of claims 1 to 12; detecting the distance (D) between the electrode (26) and the sample plane (22), and adjusting a mounting position of the electrode (26) if the distance (D) deviates from a desired distance.

15. 15. The method of claim 14, further comprising detecting a height (H) of the replaceable spark unit (10) and adjusting the height (H) of the replaceable spark unit (10) if the height (H) deviates from a desired height.

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