Emission stand for emission spectroscopy with improved dust removal.

Abstract

An emission stand (201) for an optical emission spectrometer, comprising a discharge box (210) and at least one auxiliary gas conduit (209a, 209b) for supplying an auxiliary gas flow into the discharge box (210), the at least one auxiliary gas conduit (209a, 209b) being configured to supply an auxiliary gas flow (214) into the discharge box (210) for a period of time after a spark action, but not during a spark action during which an analysis of a sample is performed. The auxiliary gas flow (214) into the discharge box (210) improves dust flushing from the discharge box (210) after the spark action.

Description

Technical Field

[0001] The present disclosure relates to the field of spark emission spectroscopy. Specifically, the present disclosure relates to an improved emission stand for an emission spectrometer, an emission spectrometer comprising the same, and a method of emission spectroscopy.

Background Art

[0002] Arc / spark emission spectroscopy is a well-known technique used for the analysis of solid samples, typically metal samples. Emission spectroscopy can be performed using either a spark light source or an arc light source, or both. For convenience, as used herein, the term spark emission spectroscopy means any emission spectroscopy that uses an electric discharge for the excitation of a sample, such as a spark discharge or an arc discharge, and the term discharge box means the space or volume for causing such an electric discharge where light is emitted and measured.

[0003] During use, a conductive (typically metallic) solid sample is mounted on a light-emitting stand above an opening leading to the discharge chamber. The sample is usually flat and therefore forms an airtight seal with the stand. Inside the discharge chamber, an electrode, usually acting as the anode, is positioned and oriented so that its tapered end faces the sample. The electrode is surrounded by an electrical insulator, except for its tapered end. A series of discharges are initiated between the electrode and the sample, with the sample acting as the cathode. The insulator ensures that the discharge is directed towards the sample and not the walls of the chamber. The sample material in the area to which the discharge is directed is exfoliated / evaporated, and some of the exfoliated / evaporated material becomes excited. Upon relaxation, the exfoliated and excited material emits photons whose energy (wavelength) is specific to a given state transition of elements in the material. Spectroscopic analysis of the emitted photons can be used to estimate the composition of the sample material. Therefore, some of the light emitted by this discharge is sent from the discharge chamber to an analyzer for spectroscopic analysis. Spectroscopic analysis is performed using an optical analyzer, typically employing dispersion means such as diffraction gratings to spatially disperse light according to its wavelength. The analyzer is equipped with a photodetector, such as an array detector, to measure the amount of light as a function of wavelength in order to obtain an emission spectrum.

[0004] To obtain information about the diverse elements in a sample, the instrument needs to be able to deliver photons of less than 200 nm from the discharge chamber to the detector, because some elements emit photons in the vacuum ultraviolet (VUV) wavelength range when relaxing to lower energy states. To avoid absorption of these VUV photons by air and to avoid wavelength shifts due to changes in the gas refractive index (which vary with gas pressure and composition), the sample material is excited in the presence of a substantially ultraviolet-transmissive inert gas, typically argon, which is supplied into the discharge chamber for at least the duration of a series of spark discharges. If the gas composition is kept constant within the spectrometer, the refractive index shift problem is eliminated, and steady-state photodetection can be performed.

[0005] The problem is that atoms, aggregates, or particles (referred to herein as debris or dust) of material detached from the sample surface may remain in the discharge chamber and / or re-deposit, potentially affecting subsequent measurements. To prevent cross-contamination, or the so-called memory effect, preferably, all material detached from one analyzed sample should be removed from the discharge chamber before analyzing the next sample, so that no material from the previous sample is redeposited on the next sample, and so that no such material is present in the discharge path. The gas flowing through the discharge chamber is used in a continuous or semi-continuous process to sweep away detached material such as metal dust and debris from the discharge chamber. In this way, much of the detached material is carried away by the gas flow from the discharge chamber to a downstream filter.

[0006] One specific design of a discharge chamber using gas flow is disclosed in International Publication No. 2012 / 028484(A1) (Thermo Fisher Scientific). However, dust is not completely removed, and over time, detached sample material may still deposit and accumulate on the insulator, as well as on other surfaces and gas conduits within the discharge chamber. This degrades the analytical performance of the spectrometer, and when this occurs, the spectrometer cannot be used while the discharge chamber is being cleaned or some components are being replaced, increasing maintenance costs and instrument downtime. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2012 / 028484 [Patent Document 2] International Publication No. 2020 / 200757 [Overview of the project] [Problems that the invention aims to solve]

[0008] One way to address the prevention of dust accumulation across multiple analysis cycles is to use a strong gas flush sequence through the discharge chamber, which is performed at the end of each spark analysis sequence. However, the direction of the strong gas flush is identical to that of the flash used during spark analysis, and in some discharge chamber designs, such as the one disclosed in International Publication No. 2012 / 028484(A1), it remains largely laminar. This is not very efficient for dust removal from the discharge chamber.

[0009] Considering the above, this disclosure is presented. [Means for solving the problem]

[0010] According to one aspect of the present disclosure, a light emission stand for an emission spectrometer is provided, the light emission stand comprising a discharge box and at least one auxiliary gas conduit for supplying an auxiliary gas flow into the discharge box, the at least one auxiliary gas conduit configured to supply an auxiliary gas flow into the discharge box for a period of time after, but not during, a spark operation.

[0011] The sample is analyzed during the spark operation. An auxiliary gas flow into the discharge chamber improves the flushing of dust from the discharge chamber after the spark operation. In this way, dust is removed from the discharge chamber after the sample analysis and before the next analysis is performed. The term "dust" as used herein refers to any material resulting from the detachment of material due to the spark operation, for example, from the detachment of material from the solid surface of the sample. The period during which at least one auxiliary gas conduit supplies an auxiliary gas flow into the discharge chamber is sufficient to allow the removal of at least some, preferably most, of the dust generated by the spark operation. The period of flushing dust from the discharge chamber with an auxiliary gas flow may be performed after each spark operation and / or after multiple spark operations, for example, periodically and / or after a set number of spark operations have been performed. The period of flushing dust from the discharge chamber with an auxiliary gas flow may be performed after each spark operation and before each spark operation. Thus, in such embodiments, there may be two flushing periods between each spark operation (analysis period). The duration for which the auxiliary gas flow flushes dust from the discharge chamber can be 1 to 5 seconds, for example, about 2 seconds, 3 seconds, or 4 seconds. The auxiliary gas flow may be a continuous flow during this period, or preferably, it may consist of a series of short gas bursts or pulses, which can further improve dust removal. For example, each short gas burst or pulse may be less than 1 second (e.g., 0.1 to 0.9 seconds, or 0.1 to 0.5 seconds, or shorter, e.g., milliseconds or tens of milliseconds), for example, a few tenths of a second (e.g., 2 / 10 second, 3 / 10 second, 4 / 10 second, 5 / 10 second, 6 / 10 second, 7 / 10 second, or 8 / 10 second). This flash period typically consists of two to three stages of sparks lasting 4 to 8 seconds each (therefore, the total spark period is, for example, 10 to 25 seconds), in contrast to the duration of a typical spark operation or analysis stage, which can last, for example, 5 to 50 seconds, or 10 to 25 seconds.

[0012] In some embodiments, at least one auxiliary gas conduit is a single auxiliary gas conduit. In some embodiments, at least one auxiliary gas conduit is two or more auxiliary gas conduits, for example, three, four, or more auxiliary gas conduits.

[0013] In some embodiments, at least one auxiliary gas conduit is switchable between an open position and a closed position, i.e., between an open position that allows gas flow into the discharge chamber and a closed position that prevents gas flow into the discharge chamber. Thus, at least one auxiliary gas conduit is configured to be in the closed position during spark operation and in the open position when flushing debris from the discharge chamber (after spark operation). Normally, at least one auxiliary gas conduit may be configured to be in the closed position, for example, when the discharge chamber is not being flushed.

[0014] In some embodiments, at least one auxiliary gas conduit is provided with at least one valve to open and close the at least one auxiliary gas conduit, thereby allowing or blocking the flow of auxiliary gas into the discharge chamber. For example, this valve may be closed during the spark operation to block the flow of auxiliary gas into the discharge chamber. This valve may be opened after the spark operation to allow the flow of auxiliary gas into the discharge chamber. A controller may be provided and configured to control the gas flow as described in this disclosure. At least one valve may be controlled by the controller, which also preferably controls the spark operation. The controller may include control logic such as a processor or state machine, as well as associated control electronics for controlling the valve and / or the spark operation (e.g., voltage source, spark frequency, total spark time, etc.).

[0015] In some embodiments, the light-emitting stand further comprises a first gas conduit for supplying a first gas flow into the discharge box, at least during the spark operation. The light-emitting stand may further comprise a second gas conduit for transporting gas from the discharge box. The first and second gas conduits may be positioned opposite each other on either side of the discharge box. The second gas conduit may be connected to an exhaust or waste line that optionally includes a debris and dust filter, or to a gas recirculation line that can filter the gas to remove debris and dust before returning it to the first and / or auxiliary gas conduits. In some embodiments, the first gas conduit is for supplying the first gas flow into the discharge box during and after the spark operation, so that the auxiliary gas flow merges with the first gas flow after the spark operation. It is beneficial to continue supplying the first gas flow into the discharge box from the first gas conduit while the auxiliary gas flow is being supplied into the discharge box. This prevents dust from flowing back up the first gas conduit and reaching the optical system (spectrometer).

[0016] In some embodiments, at least one auxiliary gas conduit is configured to supply the auxiliary gas flow in a cross-flow configuration with the first gas flow. The cross-flow configuration can enable the generation of gas turbulence within the discharge chamber, preferably near where the spark is generated. If the first gas flow is configured as an axial flow through the discharge chamber along an axis from a first (inlet) conduit to a second (outlet) conduit located directly opposite, then at least one auxiliary gas conduit is configured to supply the auxiliary gas flow in the cross-axial direction, i.e., at a non-zero angle with respect to the axis of the first gas flow.

[0017] In some embodiments, the first gas flow is laminar. In some embodiments, preferably, the first gas flow is laminar during the spark operation, and this laminar flow is interrupted by an auxiliary gas flow after the spark operation. Generally, it is beneficial for the auxiliary gas flow to supply a turbulent gas flow into the discharge chamber after the spark operation.

[0018] In some embodiments, the flow rate of the auxiliary gas flow is greater than the flow rate of the first gas flow (at least greater than the first gas flow during the spark operation). For example, the flow rate of the auxiliary gas flow may be at least twice or at least three times greater than the flow rate of the first gas flow used during the spark operation, for example, 3 to 10 times or 3 to 5 times greater. In one embodiment, the auxiliary gas flow is about 15 L / min, while the first gas flow during analysis is only in the range of 2 or 3 L / min to 5 L / min. The auxiliary gas flow may consist of a series of gas bursts or pulses.

[0019] In some embodiments, at least one auxiliary gas conduit is two auxiliary gas conduits, which are positioned symmetrically (laterally) on either side of the first gas conduit. In some embodiments, where at least one auxiliary gas conduit is a single auxiliary gas conduit, the auxiliary gas conduit is positioned (laterally) on one side of the first gas conduit.

[0020] Advantageously, the auxiliary gas flow, particularly in embodiments where the auxiliary gas flow intersects the first gas flow, allows the laminar flow to be blocked, especially in the region surrounding the electrodes and the insulator surrounding the electrodes. The blocking of the first gas flow by the auxiliary gas flow, in particular, can generate gas turbulence and / or unstable vortices, which can interact with each other and produce friction and pressure fluctuation effects. This can cause accumulated debris and dust to be stirred up, resulting in improved dust removal and reduced dust accumulation. This, in turn, means a reduction in the maintenance of the instruments required. In some embodiments, the auxiliary gas flow can stir up dust while the first gas flow acts to push the dust down from the second gas conduit (gas outlet) to the exhaust. In one embodiment, a short delay time can be introduced between the operation of the auxiliary gas flow stirring up accumulated dust and the operation of the first gas flow pushing the dust out to the outlet of the discharge box.

[0021] The discharge box, or the auxiliary conduit, the first conduit, or the second conduit may each have an anti-adhesive material on their surfaces to further reduce debris or dust accumulation. The anti-adhesive material is generally a non-metallic material. The anti-adhesive material is typically a substance with a low coefficient of friction, for example, having a static coefficient of friction and a kinetic coefficient of friction of 0.5 or less, 0.4 or less, or 0.3 or less. Such materials are described in International Publication No. WO 2020 / 200757 (A1) (Thermo Fisher Scientific).

[0022] An elongated electrode having an electrode axis generally along the elongation direction is located within the discharge box. In use, generally, a gas flow, particularly a laminar flow, through the discharge box exists, for example, between a first (inlet) gas conduit and a second (outlet) gas conduit. Preferably, the wall of the discharge box, i.e., the radially facing (radially facing the electrode) wall, is curved, thereby defining an internal volume of the discharge box having a curved outer shape, preferably a cylindrical shape, i.e., the wall of the discharge box defines a cylindrical shape. The surface of such a wall may include an anti-adhesive material as described above. Preferably, the discharge box is substantially cylindrical, and the electrode is disposed substantially on the axis of the cylinder. Preferably, the first gas conduit and the second gas conduit are located on the curved inner wall of the cylinder and are located on opposite sides of the cylinder, more preferably on substantially opposite sides. Preferably, the first gas conduit and the second gas conduit are facing each other diametrically opposite on the wall of the discharge box.

[0023] The elongated electrode may have any cross-sectional shape (i.e., the cross-section across the electrode axis), but is preferably cylindrical with a tapered conical end that extends towards the sample position within the discharge chamber. Preferably, the elongated electrode has a conical tip. The elongated electrode has an axis, referred to herein as the electrode axis, which generally extends along the elongation direction, and the electrode is oriented within the discharge chamber such that the axis faces the sample position. The electrode axis is preferably disposed substantially radially centrally within the discharge chamber. In a preferred embodiment, the electrode axis also defines the axial direction of the discharge chamber, and the gas flows generally radially from a first (inlet) gas conduit on a first side of the discharge chamber to a second (outlet) gas conduit on a second side of the discharge chamber (opposite the first side). The internal shape and components of the discharge chamber may be such that turbulent flow of the gas during spark operation is substantially eliminated, but for example, as described in WO 2012 / 028484, which is preferred for analytical performance, an auxiliary gas flow supplied in accordance with the present disclosure following spark operation can create a turbulent flow that ultimately results in better removal of detached dust and debris from the discharge chamber.

[0024] The emission stand may be configured to hold a solid (conductive) sample for analysis, typically a metal sample, such that the sample faces the surface of the electrode within the discharge chamber, and / or such that the sample is typically located above an opening within the discharge chamber wall that faces the end of the emission stand or the electrode, usually with an airtight seal. The emission stand generally includes a table that covers the discharge chamber, and the table has an opening located above the discharge chamber. The table can receive the sample such that the surface can be analyzed by covering the opening with the sample so that the surface faces the electrode. A controller may be provided to control a high voltage source to cause one or more, typically a series of discharges, between the electrode and the sample during a spark operation in which the electrode functions as an anode and the sample functions as a cathode. A gas, preferably an inert gas such as argon, is supplied into the discharge chamber via a first gas conduit during spark operation and analysis.

[0025] In another aspect of this disclosure, an emission spectrometer (OES) equipped with a light-emitting stand is provided. The emission spectrometer may further include an optical analyzer for analyzing and detecting light from a discharge chamber according to its wavelength. For example, the emission spectrometer may include a spectrometer for separating the light according to its wavelength and detecting the separated light. The light is evaporated by a sparking action and emitted by an excited sample material in the excited discharge chamber. In this way, a spectrum of the emitted light, i.e., a series of emission lines, can be obtained, thereby allowing estimation of the composition of the sample material. The light-emitting stand and emission spectrometer can be used to perform emission spectroscopy.

[0026] A further aspect of the present disclosure provides a method of emission spectroscopy, which includes supplying an auxiliary gas flow into a discharge chamber via at least one auxiliary gas conduit configured to supply the auxiliary gas flow into the discharge chamber after, but not during, a spark operation. The method may be performed using the emission stand or emission spectrometer of the present disclosure. The method of the present disclosure embodies the functions of the emission stand and its components. The features of the emission stand and emission spectrometer are applied to the method with necessary modifications.

[0027] In some embodiments, the method includes supplying a first gas flow into the discharge chamber during the spark operation, for example, via a first gas conduit separate from the auxiliary gas conduit. Thus, the first gas flow may flow through the discharge chamber during the spark operation, i.e., over a series of sparks applied to the sample in the discharge chamber during the analysis of the emission from the discharge chamber. The first gas flow may be a layered gas flow. In some embodiments, the method includes transporting the gas from the discharge chamber to, for example, an exhaust line or a recirculation line via a second gas conduit during and after the spark operation.

[0028] In some embodiments, a first gas flow into the discharge chamber is supplied during and after the spark operation, such that an auxiliary gas flow merges with the first gas flow after the spark operation. The first gas flow rate may also be increased after the spark operation for dust removal. The auxiliary gas flow may be supplied in a cross-flow configuration with the first gas flow. In some embodiments, the first gas flow is laminar. In some embodiments, the first gas flow is laminar during the spark operation, and this laminar flow is interrupted by the auxiliary gas flow after the spark operation. This cross-flow can generate turbulence and vortices, which then stir up accumulated dust, resulting in better dust removal and reduced dust buildup.

[0029] The method of the present disclosure may include any of the following steps of other well-known steps of emission spectroscopy, for example, providing a solid (typically metallic) sample for analysis, typically the sample being mounted such that its surface faces the end of an electrode in a discharge chamber and / or typically the sample being positioned above an opening in the discharge chamber wall facing the end of the electrode, usually with an airtight seal; causing one or more typically a series of discharges between the electrode and the sample during a spark operation, with the sample acting as a cathode; detaching and atomizing a substance from the sample, exciting at least a portion of the vaporized substance, thereby causing the excited substance to emit photons, the energy of which is specific to the elements in the substance; and performing a spectroscopic analysis of the emitted photons, thereby enabling estimation of the composition of the sample substance, wherein a gas, preferably an inert gas, such as argon, is supplied into the discharge chamber via a gas inlet during the analysis.

[0030] This disclosure may enable better removal of debris and dust from the discharge chamber and a reduction in the accumulation of detachable materials, such as metal dust, on the surfaces within the light-emitting stand. Furthermore, this disclosure enables a reduction in metal dust accumulation, stabilization of the analytical performance of the spectrometer over long periods of operation, and a reduction in costs associated with preventive maintenance such as cleaning or replacing parts of the light-emitting stand.

[0031] Further details of this disclosure are described below in examples with reference to the attached drawings. [Brief explanation of the drawing]

[0032] [Figure 1] This document illustrates one embodiment of a light-emitting stand for OES analysis that has a gas flow. [Figure 2] This shows a cross-section of a light-emitting stand for OES analysis according to one embodiment of the present disclosure. [Figure 3] The gas flow rate into the discharge chamber is shown as a function of time for the spark operation, which involves pre-spark and post-spark flashing. [Figure 4] A cross-section of a light-emitting stand for OES analysis according to a further embodiment of the present disclosure is shown. [Figure 5] A cross-section of a light-emitting stand for OES analysis according to another embodiment of the present disclosure is shown. [Figure 6] The OES spectrometer equipped with a light-emitting stand as described herein is schematically shown. [Modes for carrying out the invention]

[0033] Figure 1 shows a horizontal cross-sectional view of the emission stand 101, which constitutes part of the emission spectrometer. The emission stand comprises a discharge box 110 having a substantially cylindrical, i.e., cylindrical discharge box wall. The discharge box houses a cylindrical electrode 104, which is located in the center of the discharge box and surrounded by an insulator 103 to prevent discharge to the discharge box wall. The insulator 103 is rotationally symmetric with respect to the electrode 104. The figure of the emission stand 1 is separated from the other parts of the emission spectrometer. For example, the optical system (such as a spectrometer) that receives light from the discharge box is not shown.

[0034] During operation, a spark or discharge is ignited between an electrode 104 located inside the discharge chamber and the surface of a conductive sample (not shown) directed towards the discharge chamber. This spark action generates plasma, causing detachment, atomization, excitation, and subsequent emission of material from the sample. The light is analyzed by an optical system (not shown), and information regarding the composition of the sample is determined from qualitative and quantitative spectroscopy. Typically, the spark action involves a timed sequence of sparks, and the light emitted as a result of each spark is analyzed.

[0035] Spark ignition is performed under an inert gas atmosphere, such as an argon (Ar) atmosphere, which is supplied by an argon gas flow entering the discharge chamber 110 through a first gas conduit 102. The gas conduit 102 is supplied from an upstream gas source (not shown). The gas flows in the direction indicated by arrow 112. For example, during sample analysis, argon gas of a higher purity than 99.997% (e.g., Argon 48 grade, 99.998%) may be supplied into the discharge chamber through the gas conduit 102 at a flow rate of 5 L / min (standard liters per minute). A certain amount of detached material is carried out by the gas flow from the discharge chamber through a second gas conduit 108 to the discharge pipe 105. Gas conduits 102 and 108 are located on opposite sides of the discharge chamber 110. The gas conduits may be provided by channels formed within the light-emitting stand 101.

[0036] When the spark or arc sequence is completed, a certain amount of detached material tends to remain in the discharge chamber (as metal vapor, or dust or metal deposits). Some of this material may remain as metal vapor or dust, while some of the atomized metal dust may rejoin, settle, accumulate, and / or partially metallize above the insulating region 103 surrounding the central electrode 104 and / or on the walls of the discharge chamber 110 and / or on the tip of the electrode. Over multiple analysis cycles, i.e., multiple sparks, the detached material thus adhering to the insulator 103 and discharge chamber 110 can cause performance degradation and require periodic maintenance by cleaning the insulator 103, discharge chamber 110, or other parts of the light-emitting stand 101.

[0037] One technique to prevent dust accumulation over several analysis cycles is to use a powerful gas flush sequence performed at the end and / or beginning of each spark / arc sequence. The direction of the gas flush is also indicated by arrow 112. Typically, the flow rate during such a flash is several times greater than the flow rate during spark / arc operation. Due to the geometric configuration of the discharge box, the gas passing through conduit 102 and discharge box 110 remains in a substantially laminar flow. This flow (laminar flow) reduces plasma oscillations, which is advantageous during the operation of the spark / arc sequence and when performing analysis, but it is not very efficient for dust removal once the spark / arc sequence is finished. Accumulation of dust deposits leads to performance degradation and, at best, requires very time-consuming manual maintenance. At worst, it requires periodic replacement of several spark components, increasing instrument maintenance costs.

[0038] Figure 2 shows one embodiment that improves dust removal, and therefore maintenance, and reduces the operating costs of the emission spectrometer. The emission stand 201 has many of the same components as the emission stand 101, including a discharge box 210, electrodes 204, an insulator 203, a first gas conduit 202 for carrying a first gas flow 212, a second gas conduit 208, and an exhaust pipe 205. The emission stand 201 differs from the emission stand 101 in that it includes two additional gas conduits 209a, 209b that function as auxiliary gas conduits. The gas conduits 209a, 209b carry the same gas as the first gas conduit 202, such as argon. However, in other embodiments, the gas conduits 209a, 209b may carry different inert gases to flush the discharge box. Considering that the electrode 204 is oriented longitudinally (outside the page of the figure), the gas flow tubes 209a and 209b are positioned laterally on both sides of the first gas conduit 202, and at the same distance from it. Each gas flow tube 209a, 209b is connected to a valve (not shown) which, when open, allows gas flow for flushing, and when closed, blocks gas flow. In some embodiments, each tube may be connected to its own valve, or both tubes may be connected to a common valve. The valve may be a solenoid valve, a gate valve, a needle valve, or any other suitable type of gas valve.

[0039] During the analysis of the spark operation and light emission, the valves are closed to block the gas flow from entering the discharge chamber through the gas conduits 209a and 209b. Thus, the gas flow into the discharge chamber 210 during the spark operation is supplied by the first conduit 202, as indicated by arrow 212, and is preferably a laminar flow determined by the geometry of the discharge chamber 210 and the positions of the first and second gas conduits 202 and 208.

[0040] After the spark operation and analysis are complete, a flash operation can be initiated for a period of time to remove dust generated by the detachment of solids during the spark operation from the discharge chamber. For such an operation, a valve is switched and opened, allowing gas 214 to flow into the discharge chamber as two auxiliary argon gas flows 207a, 207b, which intersect and overlap with the central argon gas flow 212 through the first conduit 202, via gas flow tubes 209a, 209b. The outlets of gas flow tubes 209a, 209b are oriented so that the auxiliary gas flows 207a, 207b are generally directed toward the center of the discharge chamber, i.e., toward the vicinity of the spark electrode 204. Thus, the two peripheral auxiliary gas flows 207a, 207b cross or intersect with the central first gas flow 212.

[0041] The flow rates of the auxiliary argon gas streams 207a and 207b are preferably greater than the flow rate through the first gas conduit 202 during the spark operation / analysis. In this embodiment, the first gas flow rate through the first gas conduit 202 during the spark operation and sample analysis may be in the range of 2 to 5 L / min or 3 to 5 L / min. For the flash operation, the gas flow rate of the central gas stream through the first gas conduit 202 is increased. For example, the gas flow rate through the first gas conduit 202 is increased by 2 to 10 times, or 2 to 5 times, to, for example, 15 L / min, during the flash operation. However, in other embodiments, other flow rates more suitable for that particular system may be selected. At the same time, for the flash operation, valves on the auxiliary gas conduits 209a and 209b are opened to allow the auxiliary gas streams 207a and 207b to flow into the discharge box, and these gas streams have a gas flow rate similar to the increased central gas flow rate through the first gas conduit 202, for example, 15 L / min. A given flow rate of the auxiliary gas flow is the sum of the flow rates through the two auxiliary gas conduits 209a and 209b. Therefore, the flash operation includes a total flow rate of 30 L / min through the discharge box, consisting of a flow rate of 15 L / min for gas flow 212 and a total flow rate of 15 L / min for auxiliary gas flow 214. The pressure or velocity of the auxiliary gas flow 214 also depends on the diameters of the auxiliary gas conduits 209a and 209b. For the aforementioned gas flow rates, a suitable inner diameter for the auxiliary gas conduits 209a and 209b may be 0.5 to 5 mm, which achieves sufficient gas pressure or velocity into the discharge box for flashing.

[0042] The high-speed cross-flow configuration of the auxiliary gas flow enables the disruption of laminar flow in the region surrounding the electrode 204 and insulator 203, creating turbulence in the gas flow. Such turbulence is thought to interact with each other, resulting in unstable vortices that increase frictional effects and drag due to pressure fluctuations. This has been shown to lead to better exhaust dust removal from the discharge chamber, reduced dust buildup, and an overall improvement in maintenance conditions.

[0043] After the flash is complete, the auxiliary flow tubes 209a and 209b are closed again by closing their valves. In some embodiments, the flash operation may be performed at the end of each spark / arc sequence, while in other embodiments, the flash operation may be performed less frequently, for example, after a certain number of spark / arc sequences. A typical flash operation may last from a few tenths of a second to a few seconds. The flash duration may be 1 to 5 seconds, for example, about 2 or about 3 seconds. However, in some embodiments, the flash duration may be shorter or longer than this range. The auxiliary gas flow, and the first gas flow where applicable, may be a continuous flow during the period, or more preferably, may consist of a series of short gas pulses to assist in dust removal. For example, each short gas burst may last less than 1 second, for example, a few tenths of a second or less than 1 / 10th of a second. This flash period can last, for example, 10–25 seconds, and typically consists of 2–3 stages, each stage containing a spark of 4–8 seconds (thus the total spark action is, for example, 10–25 seconds), in contrast to the duration of a typical spark action or analysis stage.

[0044] A flash operation to remove dust from the discharge chamber by an auxiliary gas flow may be performed after and before each spark operation. Therefore, there may be two flash periods between each spark operation or analysis period. This sequence is schematically shown in Figure 3, which shows the gas flow rate into the discharge chamber as a function of time of the spark operation with a pre-spark flash operation and a post-spark flash operation. The trace (A) above shows the gas flow rate of the first gas flow 212 over time. The first gas flow 212 is the first period t, which is the pre-analysis flash period. pre The flow rate is maintained at a steady flow rate (3 L / min in this embodiment) until the analysis is complete. pre During this time, the flow rate of the first gas stream 212 increases in a series of gas bursts, i.e., pulses (for simplicity, three bursts of 15 L / min are shown). As shown by the trace below (B), the auxiliary gas stream is in the pre-analysis flash period t preIt remains off until the auxiliary gas conduit is opened, releasing the auxiliary gas flows 207a and 207b as a series of gas bursts that coincide in time with the gas burst in the first gas flow 212 (in this embodiment, the same flow rate as the burst in the first flow, i.e., 15 L / min gas bursts). The gas bursts can be brought about by the rapid opening and closing of valves on each gas conduit. Analysis period t analysis When it reaches this point, the auxiliary gas flows 207a and 207b are switched off again, and the first gas flow 212 decreases to a steady flow of 3 L / min. Under this low, stable laminar flow of the first gas flow, t analysis A spark occurs inside the discharge box, and the luminescence is analyzed. At the end of the spark, during period t post During the post-analysis flush operation, a post-analysis flush is performed. Similar to the pre-analysis flush, the flow rate of the first gas stream 212 during the post-analysis flush increases from 3 L / min to 15 L / min in a series of gas bursts, and the auxiliary gas conduit is opened again to release auxiliary gas streams 207a and 207b as a series of 15 L / min gas bursts. Post-analysis flush period t post Later, auxiliary gas flows 207a and 207b are switched off again, and the primary gas flow 212 decreases to a steady flow of 3 L / min. This cycle is repeated for each analysis performed.

[0045] Embodiments of the present disclosure advantageously allow a controlled, e.g., laminar gas flow through the discharge chamber during the spark / arc sequence by supplying gas flow through the central gas conduit 202 while auxiliary gas conduits 209a, 209b are closed by valves. This enables the most important thing for reproducible and accurate analytical results: stable and optimal analytical conditions within the discharge chamber during the spark / arc sequence. If dust flushing is required, the controlled, e.g., laminar gas flow can be interrupted by supplying auxiliary gas flow from the auxiliary gas conduits 209a, 209b by opening the valves, thereby resulting in a high-speed cross-flow that creates turbulence to aid in dust removal.

[0046] Further embodiments are shown in Figure 4. The light-emitting stand 301 has many of the same components as the light-emitting stand 201, including a discharge box 310, an electrode 304, an insulator 303, a first gas conduit 302 for carrying a first gas flow 312, a second gas conduit 308, and an exhaust pipe 305. The light-emitting stand 301 is entirely similar to the light-emitting stand 201, but differs mainly in that the stand 301 has a single auxiliary gas flow tube 309. The auxiliary gas flow tube 309 is positioned laterally to the side of the first gas conduit 302. A valve (not shown) is provided upstream of the gas flow tube 309 to open and close the gas flow tube to the auxiliary gas flow 314. When open, the auxiliary gas flow 307 is directed into the discharge box. The advantage of the embodiment in Figure 4 is that it generates turbulence in both the x and y dimensions within the region surrounding the insulator 303 and the electrode 304. This allows exhaust dust to be more efficiently lifted and removed in the gas flow, thereby improving dust removal and overall maintenance. In the embodiment shown in Figure 2, when two lateral auxiliary flow tubes are provided, strong turbulence is generated, particularly in the x-dimension, but these are almost canceled out in the y-dimension due to geometric symmetry. Nevertheless, the advantage of the embodiment in Figure 2 is that it supplies an auxiliary flow aimed at lifting the dust and actively pushing it toward the outlet conduit 308 in the x-dimension to remove it, thus avoiding any recirculation within the discharge box 310 and ensuring that this dust is collected through the exhaust pipe 305.

[0047] Another embodiment is shown in Figure 5. The light-emitting stand 501 has many of the same components as the light-emitting stand 201, including a first gas conduit 502 for carrying a first gas flow 512, and a second gas conduit 508 for collecting and removing the gas flow. The light-emitting stand 501 is similar to the light-emitting stand 201, but differs mainly in that the stand 501 has four auxiliary gas flow tubes 503a, 503b, 503c, and 503d. The four auxiliary gas flow tubes are oriented in an X configuration, or cross configuration, so that their auxiliary gas flows are directed toward the center of the discharge box, i.e., toward the vicinity of the spark electrode. Thus, the four auxiliary gas flows cross or intersect with the central first gas flow 512 in the discharge box, creating turbulence for removing dust from the discharge box.

[0048] One embodiment of an OES spectrometer comprising the light-emitting stand of the present disclosure is schematically shown in Figure 6. The light-emitting stand 401 comprises a discharge chamber 409 housing a spark electrode 422 facing the sample 420 to be analyzed. A controller 430, comprising a computer or other processor and associated control electronics for controlling a high-voltage discharge, is connected to the light-emitting stand to initiate a high-voltage spark / arc discharge between the electrode and the sample. During the spark operation and analysis of the sample, light 440 emitted from the discharge chamber is collected and detected by an optical analyzer 420, such as a spectrometer. The detection signal from the optical analyzer 420 is transmitted to the controller 430 for storage and processing by the computer or other processor to generate emission data (e.g., spectrum or light intensity at a specific wavelength) and determine information regarding the composition of the sample. The controller 430 further controls an argon gas source 410 that supplies gas into the discharge chamber via a first central gas conduit 402. The gas flows through the discharge chamber and is carried away to an exhaust line 408 by a second gas conduit. The argon flow is supplied through the discharge chamber via the central gas conduit 402 during the spark operation. After the spark operation, the controller 430 initiates a flash operation, opening valve 406a on auxiliary gas line 403a and valve 406b on auxiliary gas line 403b, respectively, which were previously closed during the spark operation. The auxiliary gas lines 403a and 403b supply a high-speed (preferably pulsed) cross-flow of argon gas that intersects with the central flow from conduit 402 within the discharge chamber, stirring up dust within the discharge chamber and assisting in the removal of dust into the exhaust line 408. After flashing with argon from auxiliary gas lines 403a and 403b, the controller closes valves 406a and 406b again in preparation for the next spark operation and sample analysis. A further flash operation may be performed immediately before the next spark operation and sample analysis.

[0049] It will be recognized that modifications to the embodiments described herein may still be made within the scope of the herein.

[0050] Any and all examples or illustrative phrases provided herein (such as “for instance,” “such as,” “for example,” and similar phrases) are intended merely to better illustrate the invention and, unless specifically claimed, do not imply any limitation to the scope of this disclosure. Nothing in this specification should be construed as indicating any element not claimed to be essential to the practice of this disclosure.

[0051] Where used herein, including in the claims, the singular form of a term shall be interpreted as including the plural form, and vice versa, unless otherwise indicated by context. For example, where otherwise indicated by context, the singular demonstrative pronouns herein, including in the claims, such as "a" or "an," mean "one or more."

[0052] Throughout this specification and in the claims, the terms “comprise,” “including,” “having,” and “contain,” as well as variations thereof, such as “comprising” and “comprises,” and others, mean “including, but not limited to,” and are not intended to exclude other components.

Claims

1. A light-emitting stand for an emission spectrometer, Discharge box and A first gas conduit for supplying a first gas flow into the discharge box, at least during spark operation, A second gas conduit for transporting gas from the discharge box, The system comprises at least one auxiliary gas conduit, separate from the first gas conduit, for supplying an auxiliary gas flow into the discharge box, wherein the at least one auxiliary gas conduit is configured to supply the auxiliary gas flow into the discharge box for a period of time after the spark operation, not during the spark operation, The first gas conduit is for supplying the first gas flow into the discharge box both during and after the spark operation, so that the auxiliary gas flow merges with the first gas flow after the spark operation. The at least one auxiliary gas conduit is configured to supply the auxiliary gas flow in a cross-flow configuration with the first gas flow, The aforementioned cross-flow configuration enables the generation of gas turbulence within the discharge box near where the spark is generated, in a light-emitting stand.

2. The light-emitting stand according to claim 1, wherein the at least one auxiliary gas conduit is a single auxiliary gas conduit.

3. The light-emitting stand according to claim 1, wherein the at least one auxiliary gas conduit is two or more auxiliary gas conduits.

4. The light-emitting stand according to any one of claims 1 to 3, wherein the at least one auxiliary gas conduit is switchable between an open position and a closed position.

5. The light-emitting stand according to claim 4, wherein the at least one auxiliary gas conduit is provided with at least one valve for opening and closing the at least one auxiliary gas conduit, thereby allowing or preventing the auxiliary gas flow from entering the discharge box.

6. The light-emitting stand according to any one of claims 1 to 3, wherein the first gas flow is laminar during the spark operation, and the laminar flow is interrupted by the auxiliary gas flow after the spark operation.

7. The light-emitting stand according to any one of claims 1 to 3, wherein the flow rate of the auxiliary gas flow is greater than the flow rate of the first gas flow during the spark operation.

8. The light-emitting stand according to any one of claims 1 to 3, wherein the at least one auxiliary gas conduit is two auxiliary gas conduits, and the two auxiliary gas conduits are symmetrically positioned on both sides of the first gas conduit.

9. The light-emitting stand according to any one of claims 1 to 3, wherein the auxiliary gas flow includes a series of gas pulses.

10. An emission spectrometer comprising a light-emitting stand according to any one of claims 1 to 3.

11. A method of emission spectroscopy, At least during the spark operation, a first gas flow is supplied into the discharge box via a first gas conduit, The gas is transported from the discharge box via a second gas conduit, This includes supplying an auxiliary gas flow into the discharge box via at least one auxiliary gas conduit, separate from the first gas conduit, which is configured to supply the auxiliary gas flow into the discharge box not during the spark operation, but for a period of time after the spark operation, The first gas conduit is for supplying the first gas flow into the discharge box both during and after the spark operation, so that the auxiliary gas flow merges with the first gas flow after the spark operation. The at least one auxiliary gas conduit is configured to supply the auxiliary gas flow in a cross-flow configuration with the first gas flow, The cross-flow configuration is a method that enables the generation of gas turbulence within the discharge box near where the spark is generated.

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