Exchangeable spark unit, system, and calibration method

Abstract

To provide a spark unit, a system, and a calibration method that enable a fast and easy replacement of a spark unit.SOLUTION: An exchangeable spark unit 10 for an optical emission spectrometer 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 in a distance D to the sample plane 22 in a 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 for emitting 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; and an optical component 44 for influencing the emitted light.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] During different stages of metallurgical steel processing, e.g., converter processing, samples are taken from molten steel and analyzed to determine its chemical composition. This allows for process control and the adjustment of the resulting steel's properties. Typically, spark optical emission spectroscopy (OES) is used to determine the chemical composition of steel samples. In this method, electrical energy is used to generate a spark between a solid steel sample and an electrode, as described, for example, in U.S. Pat. No. 5,285,251. Through this, atoms or ions in 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 allows for the determination of the chemical elements present. Using a suitably calibrated system, the quantity of the sample, and therefore its chemical composition, can be determined. Such methods are disclosed in U.S. Pat. Nos. 4,592,655 (A), 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 location, i.e., the steel plant. Therefore, 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 economically advantageous for metal producers. Various solutions to this problem are described in European Patent Nos. 3336511(A1), 3336512(A1), 3336513(A1), 3336514(A1), 3581913(A1), and 3581914(A1). These documents relate to a type of molten metal immersion sampler that produces Direct Analysis (DA) samples. DA samples do not require any type of surface preparation prior to analysis, and therefore, utilizing spark-OES analysis can provide significant economic benefits in terms of both the availability of timely chemistry results and laboratory time savings.

[0005] During spark OES, particles detached from the sample by the spark contaminate the spark chamber and adjacent areas of the spectroscopic analyzer. These particles can accumulate on optical elements such as windows, mirrors, lenses, or detectors and must be removed to ensure consistent analysis quality. Because 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 minutes. Such systems are disclosed in International Publication No. 2021 / 048382 (A2) and British Patent No. 2592853 (A), which are from the same family, as well as U.S. Patent Publication No. 2021 / 0285820 (A1). A handheld device for spectroscopic analysis is known from U.S. Patent No. 4411524 (A). Summary of the Invention [Problem to be solved by the invention]

[0006] However, known spectroscopic analyzers must be calibrated or recalibrated after replacing the spark unit in order to obtain reliable results. Due to the nature of the analysis, even small deviations from the desired value lead to significant differences in the analyzed light and therefore 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 light intensity and, if applicable, a change in light composition. Different deviations can accumulate. However, replacing and recalibrating 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] A replaceable spark unit for an optical emission spectrometer serves to solve the problem. The replaceable spark unit comprises a sample carrier defining a sample plane for positioning a sample to be analyzed. The sample carrier has an aperture. The replaceable spark unit comprises an electrode arranged at a distance from the sample plane in the region of the aperture so that a spark can be generated between the electrode and a sample positioned in the sample plane to emit light. The replaceable spark unit further comprises a coupling interface for mechanically coupling the replaceable spark unit to the optical emission spectrometer and optical components 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, electrodes, and 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 present invention includes optical components that affect light before it enters the optical emission spectrometer. Therefore, some of the optical effects and processing required to analyze the optical spectrum of the spectrometer to determine the composition of a 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 present invention therefore allows a portion of the path traveled by light between the spark and the spectrometer to be fixedly defined within the spark unit. Therefore, it is possible to replace a contaminated replaceable spark unit with a new, already calibrated one that defines the exact same optical path. Most of the optical path is unaffected by replacing the spark unit. Therefore, there is no need to recalibrate the entire instrument after replacing a spark unit according to the present invention.

[0013] Specifically, the replaceable spark unit and optical emission spectrometer analyzer are used to analyze samples during the steelmaking process in steel plants near converters. Therefore, the device must function reliably under harsh conditions, including heat and contamination. Therefore, quick and easy replacement of the replaceable spark unit is required. Additionally, in this environment, samples must be analyzed regularly at 30-45 minute intervals. For this reason, spark unit replacement must be completed in less than 20 minutes. This is possible with the replaceable spark unit of the present invention, since no recalibration is required. Long-term operation of the spectrometer can be achieved by regularly replacing the spark unit.

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

[0015] The electrode is disposed in the aperture region. This allows a spark to be generated between the electrode and a sample positioned in the sample plane. Specifically, the electrode is disposed 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 which is 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, specifically 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 disposed essentially vertically. Specifically, 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, specifically 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 therefore 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, can form the upper surface of an exchangeable spark unit. The sample is in particular a metal sample.

[0017] The spark emits 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. Hereinafter, the optical emission spectrometer will be 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 present 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 (position in the height direction or z-direction) of the replaceable spark unit. Specifically, 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 include one or more surfaces that can be positioned adjacent to corresponding surfaces of the spectroscopic analyzer. Specifically, the replaceable spark unit can be coupled to a housing of the spectroscopic analyzer in which 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 for 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 analyzer for analysis.

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

[0021] In one embodiment, the replaceable spark unit includes a first hollow space for light to pass from the generated spark to the optical components and a second hollow space for light to pass from the optical components to the light outlet of the replaceable spark unit. The compartment containing the electrodes and optical components of the replaceable spark unit includes the first and second hollow spaces, i.e., the first and second hollow spaces form at least a portion of the volume of the compartment. 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°.

[0022] The hollow spaces serve to transmit light. Typically, the first and / or second hollow spaces have a generally cylindrical shape and / or are realized as tubes. The angle α is measured along the central longitudinal axis of each hollow space, which may define the centerline through which the light passes. If the angle is less than 45°, the hollow spaces are positioned far away from the electrodes, requiring a very large construction space. Specifically, the angle is greater than 90° to ensure that the sample plane is free of any obstructing components. Between 90° and 110°, optimal use of space is possible. In one configuration, the angle α is approximately 100°. Specifically, the second hollow space is at least essentially vertical.

[0023] In one embodiment, the replaceable spark unit includes a mirror as the optical component. Specifically, the optical component is a mirror for reflecting the emitted light. Thus, the light can be directed along a predetermined path and / or toward 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 toward a spectroscopic analyzer near 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 incident light with an angle β of 5° to 20°, preferably 8° to 12°, relative to the sample plane. At smaller angles, the sample plane is obstructed by the mirror. At larger angles, the spark cannot be fully represented by the emitted light. In addition, blackbody radiation from the hot sample spark region then enters the spectroscopic analyzer, leading to increased stray light levels. Thus, β may be preferably about 10°.

[0026] In one embodiment, the mirror is positioned so that the light reflected by the mirror travels essentially vertically downward. The sample plane is typically aligned horizontally. Therefore, 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 device while closing a hollow space for light to pass through the replaceable spark unit.

[0028] The windows act as optical outlets for light filtered by the optical components. Closing them helps to keep the inert gas inside each hollow space. Specifically, the windows allow light to pass from the second hollow space to the optical emission spectrometer while closing the second hollow space. To help close the second hollow space, an O-ring can be placed around a further optical component, such as a filter.

[0029] In one embodiment, the window is configured as an optical component. Specifically, the window is configured as a filter or 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 analysis by the spectrometer. The filter can be a neutral density filter. Preferably, the filter is configured to pass less than 50%, more preferably less than 30%, of the incident light. In one configuration, the filter attenuates the light intensity by a factor of 10. In one configuration, an additional optical component can be disposed in the replaceable spark unit. The additional optical component can be a lens or a filter. Thus, the filter can be disposed on top of the lens that acts as the 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, i.e., 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. Specifically, the positioning element can be selected before coupling the replaceable spark unit to the spectrometer to obtain a constant distance D. Specifically, the electrode can be adjusted in height by rotating it like a screw. It can thus be ensured that the distance D is accurate, which allows accurate measurements, particularly after replacing the spark unit, without recalibration. In one configuration, the electrode can be fixed in place when attached.

[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 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 for 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 includes a fastening means for mechanically fastening the replaceable spark unit to the optical emission spectrometer in a mechanically coupled state. Specifically, the fastening means includes one or more screws. In other words, the replaceable spark unit can be mechanically fastened to the optical emission spectrometer in a coupled state. Specifically, all degrees of freedom are constrained to achieve a stable connection between the replaceable spark unit and the optical emission spectrometer.

[0037] In one embodiment, the replaceable spark unit includes 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, where each of the other items includes a receiving space for receiving the positioning pin. The positioning pin can also be a separate element disposed inside the receiving space of the replaceable spark unit and the receiving space of the spectrometer. Specifically, the positioning pin is perpendicular to the bottom surface of the replaceable spark unit and / or the top surface of the optical emission spectrometer. The positioning pin defines the relative position along at least that surface.

[0038] In one embodiment, the replaceable spark unit includes an orientation means for achieving 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- and y-directions. In one configuration, a locating pin may be positioned off-center to serve as the orientation means. In other words, the locating pin has an offset. It may be shaped rotationally asymmetric. A suitable locating pin may serve to rotationally and translationally position the replaceable spark unit relative to the spectroscopic analyzer. Alternatively or additionally, the orientation means may include a form element, such as at least a portion of the outer contour of a component, that interacts with a corresponding form element for positioning.

[0039] In one embodiment, the sample carrier is made of a conductive material and includes 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 during use, as intended.

[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 located 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 isolated from the housing and sample carrier.

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

[0043] A further aspect of the present invention is a system for analyzing samples using optical emission spectroscopy. The system comprises a replaceable spark unit according to the present invention and an optical emission spectrometer. The optical emission spectrometer 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 spectrometer is typically located on a housing of the spectrometer, preferably forming a top surface of the spectrometer. All of the features, embodiments, and advantages of the replaceable spark unit described above are also valid for the system, and vice versa.

[0044] In one embodiment, the system comprises 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, onto a CCD detector.

[0046] A further aspect of the present invention is a method for calibrating a replaceable spark unit. The method includes providing a replaceable spark unit according to the present invention. The method further includes detecting a distance D between the electrode and a 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 the housing or another reference point on 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 the spark unit to be replaced without having 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 wearing 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 is adjusting the height of the electrode, specifically by twisting; and inserting a positioning element selected according to its height to fix the height of the electrode.

[0049] In one embodiment, the method further includes 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 part or all of the replaceable spark unit. Specifically, the height is measured between the sample plane and the coupling interface, for example, the lowest point of the coupling interface. The height H also affects the length of the optical path and therefore the analysis. Therefore, this embodiment enables highly accurate analysis.

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

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

[0052] In one configuration, the method further includes 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 detecting and adjusting distance step can, in principle, be performed in any order. However, the detecting and adjusting step is preferably performed before the coupling step, specifically before delivering the replaceable spark unit. The optional height detecting step is specifically performed before the coupling step. Thus, replacement of the spark unit can be performed particularly quickly.

[0053] In one configuration, the replaceable spark unit includes 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 comprise 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 and is not released until the final mounting block is completed. Therefore, particularly low tolerances on distances, lengths, and angles are possible, which are not possible using conventional machining tools.

[0054] In the following, exemplary embodiments of the present invention will be described in detail with reference to the drawings. 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 explanation of the drawings]

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

[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 comprises, on its underside, a coupling interface 30, which is realized as a horizontal surface, and the optical emission spectrometer 12 comprises, on its upper side, 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 an optical slit, a collimating mirror, a diffraction grating, a focusing mirror, and / or a detector such as a CCD detector. 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 includes a sample carrier 20 defining a sample plane 22 on which a sample to be analyzed can be positioned. The sample carrier 20 is formed by the top wall of the housing 28 of the replaceable spark unit 10. The sample plane 22 corresponds to the top surface of the replaceable spark unit 10. The sample carrier 20 includes an aperture 24 formed therein. The replaceable spark unit 10 further includes an electrode 26 positioned below the center of the aperture 24 and at a distance from the sample plane 22. 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 whose composition depends on the composition of the sample. The light travels from the spark location, through the replaceable spark unit 10, and downward through a window 47 to the optical emission spectrometer 12 for analysis.

[0059] FIG. 2 shows an enlarged view of detail "A" in 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, 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, filter, or prism. In the configuration shown, the centerline 29 forms an angle β of approximately 10° with respect to the sample plane 20. Light reflected by the mirror 45 travels vertically downward toward the light outlet 46 through which it exits the replaceable spark unit 10 and subsequently enters the optical emission spectrometer.

[0060] Light passes from the spark location to a mirror 45 inside a first hollow space 41. A large portion of the first hollow space 41 is configured as a cylindrical tube. The light reflected by the mirror 45 passes through a second hollow space 42, which is also largely configured 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 that closes the second hollow space 42 in a downward direction. The window 47 can be configured as a further optical component, namely a filter 48 that allows only a part of the incident light to pass through the optical emission spectrometer.

[0062] The gas inlet 55 is located near the lower 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. Specifically, an inert gas heavier than air, such as argon, can be introduced into the gas inlet 55 to gradually fill the second hollow space 42 from bottom to top. As more inert gas is introduced, the first hollow space 41 and then the third hollow space 43 also fill. Some 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, a continuous gas flow occurs during an analysis. High volumetric flow can occur during sparking and / or low volumetric flow can occur between sparking events. 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 downward to exit through the gas outlet 56.

[0063] The electrode 26 is essentially pen-shaped and vertically aligned. At its bottom, it has an electrical connection 2 for applying an electric potential between the electrode 26 and the sample. At its top, it has 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., between the electrode tip and the sample, may be 2.0 mm. The electrode 26 has a peripheral shoulder 51 that forms a horizontally aligned bearing surface 50. The electrode 26 rests on a positioning element 52 that may be disposed around the outer periphery of the electrode 26 or at least a portion of the outer periphery. 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, replaceable spark unit 10 is configured so that positioning element 52 can be removed and replaced with another positioning element 52. In that case, distance D can be adjusted by replacing positioning element 52. In this manner, the desired distance can be precisely adjusted, eliminating the need to calibrate the system before taking measurements, even after replacing 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 realized as spark pins made of tungsten, as shown in FIG.

[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 directly or indirectly hold or form different components. 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 includes a top portion that contains the sample carrier 20 and at least a portion of the first hollow space 41. The top portion is a separate component that may be fixedly attached to the mounting block. An O-ring is positioned in the horizontal plane between the top portion and the mounting block to seal the third hollow space 43 against leakage of inert gas. The overall height H of the replaceable spark unit 10 may be adjusted by affecting the height of the top portion. This may be done with the mounting block attached to the top portion as shown, or with the top portion separated from the mounting block.

[0067] When replacing the replaceable spark unit 10, the electrical connection 2 on the electrode 26 can be loosened. Specifically, 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, forming a plane, and the coupling interface 32 of the optical emission spectrometer 12 is formed accordingly. Receiving spaces 65 are arranged in the replaceable spark unit 10 to receive positioning pins 64 and facilitate proper positioning of the replaceable spark unit 10 relative to the optical emission spectrometer.

[0069] 3 shows a perspective view of a system 15 including a replaceable spark unit 10 and an optical emission spectrometer 12. Shown are flange-like protrusions at the bottom end of the replaceable spark unit 10 and the top 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 insulator 2 Electrical Connections 10 Replaceable Spark Units 12 Optical emission spectrometer 13 Spectroscopic analyzer 15 Systems 20 Sample Carrier 22 Sample plane 24 aperture 26 electrodes 28 Housing 29 Center line 29' center line D distance H Height 30 Bonding Interfaces 32 bonded interfaces 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 spectroscopy 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) with the optical emission spectroscopy 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, wherein the replaceable spark unit (10) comprises a first hollow space (41) for light to pass from the generated spark to the mirror (45) and a second hollow space (42) for light to pass from the mirror (45) towards a light outlet (46) of the replaceable spark unit (10), characterized in that 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 light reflected by the mirror (45) travels essentially vertically downwards.

5. 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, wherein 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, wherein 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. 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. 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 the positioning pin (64).

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

12. 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 comprises electrical contacts for applying an electric potential via the sample carrier (20) to the sample positioned on the sample carrier (20).

13. 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 spectrometer (12), in particular a Czerny-Turner spectrometer (13), the optical emission spectrometer (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 the 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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