Rotational flow air curtain type laser-induced breakdown spectroscopy atmosphere control device

Abstract

The invention discloses a rotational flow air curtain type laser-induced breakdown spectroscopy atmosphere control device, and belongs to the technical field of laser-induced breakdown spectroscopy detection. The device comprises a shell, an air inlet, a pressure equalizing cavity, an air spraying hole, a through pipe and an air outlet. The pressure equalizing cavity is communicated with the gas inlet and the gas spraying hole for gas supply, the gas is sprayed into the annular space flow channel from the pressure equalizing cavity through the gas spraying hole, the gas outlet is formed in the outlet end of the shell and communicated with the annular space flow channel, the gas forms continuous gas flow in the annular space flow channel and is discharged from the gas outlet, and therefore a continuous gas curtain is formed in the circumferential direction of the outlet area; the atmosphere control device realizes effective atmosphere control on a measurement area, is simple in structure, does not depend on a rotating mechanism and a contact type sealing structure, can quickly form a stable local controlled atmosphere near a sampling point through an efficient flow field organization, and still keeps a device structure with a good atmosphere control effect at a relatively low gas flow rate; therefore, the measurement stability and the result reliability are improved.

Description

Technical Field

[0001] This invention relates to a swirling gas curtain type laser-induced breakdown spectroscopy atmosphere control device, belonging to the field of laser-induced breakdown spectroscopy (LIBS) detection technology. Background Technology

[0002] Laser-induced breakdown spectroscopy (LIBS) is a technique that uses pulsed laser light to generate plasma on the sample surface and collects its emission spectrum to achieve qualitative and quantitative elemental analysis. The formation, expansion, and radiation processes of the plasma are significantly affected by ambient gas conditions. The composition of the ambient gas can alter the temperature and electron density evolution of the plasma, further affecting spectral line intensity, background level, and signal stability, thus impacting the accuracy and repeatability of the analytical results.

[0003] When performing LIBS measurements under certain ambient gases, specific gas components readily participate in the plasma process, introducing additional continuous background and characteristic radiation, resulting in spectral line superposition, background elevation, and signal fluctuations. When the analyte itself contains these specific elements and it is necessary to analyze its related spectral lines or content, the contributions from these specific gases will be directly superimposed on the target signal, easily leading to problems such as high blank values, difficulty in peak shape identification, and increased deviation in quantitative results. This is particularly detrimental to reliable differentiation under low content or weak spectral line conditions.

[0004] To improve measurement quality, existing studies generally employ methods such as controlling the atmosphere in the measurement area to enhance spectral performance and signal-to-noise ratio. Common practices in existing technologies include: creating a vacuum or low-pressure environment within a sealed cavity using a pumping system, and then introducing the desired ambient gas (e.g., a laser-induced breakdown spectroscopy measurement system capable of multi-point excitation disclosed in patent publication number CN114894779A); or establishing a protective atmosphere in a relatively enclosed space through pumping and displacement or continuous purging (e.g., a detection environment pressure control structure for a handheld laser-induced breakdown spectrometer disclosed in patent publication number CN109580556A). Taking a laser-induced breakdown spectroscopy detection system and method with patent publication number CN119915797A as an example, a gas supply chamber and a purge ring are set inside the shroud. The purge ring has multiple gas outlets arranged circumferentially, and a rotary motor and a friction wheel drive the purge ring to rotate continuously circumferentially, so that the gas outlets spray around the sample, thereby achieving uniform envelopment of the protective gas around the sample. At the same time, an annular sealing airbag is also set. During the purge process, the airbag is inflated so that it contacts and envelops the upper surface of the sample, thereby improving the stability and purity of the protective atmosphere inside the shroud.

[0005] However, the above-mentioned solutions usually require the lifting and lowering of the shroud and the corresponding drive and transmission structure, as well as the introduction of components such as rotary drive parts, sealing airbags, and linkage processes such as airway switching. The system configuration is more inclined to be a complete set of equipment integration, with relatively complex structure and maintenance links, complex overall structure, and high cost. Moreover, its atmosphere control mainly relies on establishing a protective space inside the shroud and maintaining it through purging and sealing, which puts requirements on the size of the device, the reliability of the mechanism, and the adaptability to the sample posture. It is difficult to apply to the field measurement or open sampling point conditions that require "miniaturization, lightweight, and rapid deployment". Summary of the Invention

[0006] To address the problems of existing spectral detection systems having complex atmosphere control structures, high costs, and limited applicability to miniaturized, lightweight, and rapidly deployable field measurements or open sampling point conditions, this invention provides a swirling gas curtain type laser-induced breakdown spectral atmosphere control device. The technical solution is as follows: A swirling gas curtain type laser-induced breakdown spectral atmosphere control device, the device comprising a housing, an air inlet, a pressure equalization chamber, an air jet hole, a through tube, and an air outlet; The through tube is disposed inside the housing and is used to provide a laser incident path, and an annular flow channel is formed between the outer wall of the through tube and the inner wall of the housing. The pressure equalization chamber is an annular cavity located inside the housing and is connected to the air inlet for air supply; the air inlet end of the jet nozzle is connected to the pressure equalization chamber, and the air outlet end of the jet nozzle is located inside the annular flow channel, so that gas is injected from the pressure equalization chamber into the annular flow channel through the jet nozzle; The gas outlet is located at the outlet end of the housing and communicates with the annular flow channel, so that the gas forms a continuous airflow around the circumference of the pipe in the annular flow channel and is discharged from the gas outlet, thereby forming a continuous air curtain in the circumference of the outlet area, and achieving effective atmosphere control in the area to be measured.

[0007] Furthermore, the outlet includes a contraction section, a short straight section, and an expansion section in sequence along the gas flow direction. The contraction section is used to converge and accelerate the incoming flow from the annular channel, the short straight section is used to rectify and stabilize the flow field, and the expansion section is used to stabilize the outward expansion of the airflow to reduce the entrainment and remixing of ambient gas in the near field of the outlet.

[0008] Furthermore, there are two jet holes, which are symmetrically arranged 160-200° apart along the circumferential direction of the pressure equalization chamber. The jet holes are arranged obliquely downward and are 60-120° away from the air inlet in the circumferential direction. The jet holes inject gas into the annular flow channel in an oblique direction, so that the gas forms a rotating flow in the annular flow channel.

[0009] Furthermore, in addition to having a horizontal oblique direction, the axis of the jet hole is also inclined downward relative to the cross-sectional plane perpendicular to the housing axis, so that the gas injected into the annular gap flow channel can more easily flow downward along the housing axis and be discharged from the outlet.

[0010] Furthermore, the axis of the jet hole is at a 30-50° angle to the tangent of the inner wall of the pressure equalization chamber, and is inclined downward at a 5-20° angle relative to the section perpendicular to the axis of the housing.

[0011] Furthermore, the radius of the jet hole is 1.1-1.5 mm.

[0012] Furthermore, the flow rate of the gas entering the inlet is 1-5 L / min.

[0013] Furthermore, the height of the through tube is 30-45mm, and the bottom of the through tube is 8-15mm away from the bottom of the shell.

[0014] Furthermore, the atmosphere control device is installed directly above the sampling point, with its outlet end maintaining a distance of approximately 2-5 mm from the sample surface.

[0015] The beneficial effects of this invention are: Gas is supplied through a pressure equalization chamber connected to the air inlet, while the jet orifice is connected to the pressure equalization chamber. This allows gas to be injected from the pressure equalization chamber into the annular flow channel through the jet orifice. The air outlet is located at the outlet end of the housing and is connected to the annular flow channel. This allows the gas to form a continuous airflow around the central pipe within the annular flow channel and exit through the air outlet, thereby forming a continuous air curtain in the circumferential direction in the outlet area. This achieves effective atmosphere control in the measurement area. The atmosphere control device of this invention has a simple structure and does not rely on a rotating mechanism or a contact sealing structure. Instead, it can quickly form a stable, locally controlled atmosphere near the sampling point through efficient flow field organization and maintain good atmosphere control even at low gas flow rates, thus improving the stability and reliability of LIBS measurements. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an atmosphere control device according to an embodiment of the present invention; Figure 2 This is a comparison of the spectra of the device of the present invention under conditions of no argon gas and argon gas. Figure 3 This is a longitudinal partial sectional view of an embodiment of the present invention; Figure 4 This is a cross-sectional view of an embodiment of the present invention; In the picture: 1. Shell; 2. Air inlet; 3. Pressure equalization chamber; 4. Air jet hole; 5. Core tube; 6. Air outlet. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0019] Example 1 This embodiment provides a swirling gas curtain type laser-induced breakdown spectral atmosphere control device. See [link to relevant documentation] Figure 1 The device includes a housing 1, an air inlet 2, a pressure equalization chamber 3, an air jet 4, a through tube 5, and an air outlet 6. The housing 1 is a cylindrical housing with an inner radius of 6-8 mm and an outer radius of 10-13 mm, and serves as a mounting base for gas flow and optical path channels.

[0020] The lower end of the through tube 5 extends into the housing 1 and is coaxial with the housing 1. The outer radius of the through tube 5 is 5-7 mm, and the inner radius is 4-6 mm. The through tube 5 provides a laser incident channel, and its hollow internal channel is also used to collect plasma radiation light and guide it to the subsequent spectral acquisition unit. An annular flow channel is formed between the outer wall of the through tube 5 and the inner wall of the housing 1, which is a downward flow channel for gas. The height of the through tube 5 is 30-45 mm, and the bottom of the through tube 5 is 8-15 mm away from the bottom of the housing 1, so that the gas injected into the annular flow channel has sufficient development length before reaching the outlet 6, which is conducive to forming a stable downward airflow.

[0021] The pressure equalization chamber 3 is located inside the housing 1 and is an annular cavity. The pressure equalization chamber 3 is used to stabilize the pressure of the incoming gas and achieve circumferential uniform distribution. The bottom of the pressure equalization chamber 3 is 14-24 mm from the bottom of the housing 1, and the height of the pressure equalization chamber 3 is 6-9 mm. The air inlet 2 is located on the side wall of the housing 1 and directly communicates with the pressure equalization chamber 3. The central axis of the air inlet 2 is 18-26 mm from the bottom of the housing 1. An outwardly extending connecting boss (not shown in the figure) is provided on the outer side of the air inlet 2 for connection to an external gas path.

[0022] The jet orifice 4 is used to introduce gas from the equalizing chamber 3 into the annular flow channel. The inlet end of the jet orifice 4 is connected to the equalizing chamber 3, and the outlet end of the jet orifice 4 is located inside the annular flow channel. In this embodiment, the outlet end of the jet orifice 4 consists of two oblique jet orifices with a radius of 1.1-1.5 mm. Figure 4As shown, the two jet holes 4 are spaced 160-200° apart along the circumference of the equalizing cavity 3, and differ from the air inlet 2 by 60-120° in the circumferential direction. The axis of the jet holes 4 forms a 30-50° angle with the tangent to the inner wall of the equalizing cavity 3. Figure 4 As shown, the cross section perpendicular to the axis of shell 1 is inclined downward at 5-20°, so that the gas enters the annular gap channel and forms a rotating downward flow pattern.

[0023] The outlet 6 is located at the outlet end of the housing 1, with its upper end connected to the annular flow channel and its lower end flush with the bottom end of the housing 1. The outlet 6 includes a contraction section, a short straight section, and an expansion section in sequence along the gas flow direction: the inner wall of the outlet 6 begins to contract from 8-15 mm away from the bottom end of the outlet 6, with an axial projection length of 3-8 mm, and the inner wall radius is 2.5-3.5 mm; then a short straight section is provided, with an inner wall radius of 3 mm and an axial length of 1-4 mm; the end of the short straight section connects to the expansion section, which terminates at the end face where the bottom end of the outlet 6 is located, and the inner wall radius expands to 3.5-5.0 mm. Specific Implementation This embodiment illustrates the effect of the atmosphere control device of the present invention in achieving atmosphere control during LIBS measurement. For example... Figure 1 As shown, a swirling gas curtain type laser-induced breakdown spectral atmosphere control device is described, wherein the air inlet 2 of the device is connected to the laser channel of LIBS.

[0025] The device was installed directly above the sample sampling point, with the bottom of the outlet 6 approximately 3 mm above the sample surface. Argon gas was used, introduced through inlet 2 at a flow rate of 5 L / min. A laser beam was incident on the sample surface through the core tube 5 to generate plasma. The plasma radiation entered the spectral acquisition system through the gap between the outlet and the sample surface. Near-infrared channels were used for data acquisition, with a laser single-pulse energy of 5 mJ, a repetition rate of 1 Hz, and a spectral acquisition integration time of 1 ms. To ensure effective comparison, all laser parameters, acquisition parameters, and optical alignment conditions were kept consistent, except for the atmospheric conditions, between the argon-gas-introduced and argon-free conditions.

[0026] The comparison conditions are set as follows: Comparative Example A: Measurements were performed directly in air without introducing argon gas; Example B: Argon gas (5 L / min) was introduced, and the measurement was performed using the device of the present invention.

[0027] like Figure 2As shown, in an air environment (Comparative Example A), obvious nitrogen-related emission characteristics can be observed in the 740–747 nm band, with clear spectral peaks near NI 742.56 nm, NI 744.52 nm, and NI 746.9 nm. However, under the condition of introducing argon gas and using the device of the present invention (Example B), the peak intensity of the above nitrogen spectral lines is significantly reduced, the overall spectrum tends to be flat, and the nitrogen-related emission signal almost disappears in this band. For ease of comparison, Figure 2 The curve under medium atmospheric conditions shifted upward by 800 au.

[0028] As can be seen from the above results, the device of the present invention does not require a sealed system or an exhaust system. It can quickly form a stable local gas environment near the sampling point by simply introducing a low flow rate of argon gas, effectively suppressing backmixing of ambient gas and significantly controlling the gas atmosphere, thereby improving the spectral line resolution and reliability of LIBS measurements.

[0029] The working principle of this invention is as follows: During operation, gas enters the equalizing chamber 3 through inlet 2. Since the equalizing chamber 3 is annular, its function is to buffer, stabilize, and evenly distribute the gas from a single inlet, ensuring a more consistent circumferential distribution during subsequent ejection and preventing damage to the protective layer caused by uneven gas supply on one side. Subsequently, the gas enters the annular flow channel through the jet nozzle 4, located between the equalizing chamber 3 and the annular flow channel. The jet nozzle 4 has two distinct characteristics: it is obliquely ejected along the equalizing chamber 3, and it has a certain downward tilt angle. The oblique ejection causes the gas to form a rotating flow after entering the annular gap, thus rapidly spreading circumferentially and ensuring a more uniform and continuous gas distribution on the outside of the core tube 5. The downward tilt angle makes it easier for the gas to achieve a stable downward trend, reducing ineffective backflow in the upper cavity and allowing the protective gas to be transported downwards close to the annular flow channel.

[0030] The gas moves downward along the annular channel between the outer wall of the core tube 5 and the inner wall of the shell 1 and gathers at the outlet end. The internal channel of the core tube 5 mainly serves as the optical path, allowing the laser to enter the sample surface through the hollow channel of the core tube 5, while the main flow path of the gas is completed in the annular channel on the outside of the core tube 5.

[0031] At the outlet, outlet 6 employs a three-section structure—a contraction section, a short straight section, and an expansion section—to shape the downward airflow. The contraction section causes the incoming flow from the annular channel to converge at the outlet, increasing momentum and making it easier for the gas to occupy the near-field of the outlet. The short straight section makes the flow more stable and improves the circumferential consistency at the outlet. The expansion section ensures that the outflow expands stably after leaving the device, forming a more complete gas curtain coverage. The device is installed directly above the sampling point, with the outlet end maintaining a distance of approximately 2-5 mm from the sample surface. Plasma radiation enters the spectral acquisition system through the gap between the outlet and the sample surface. After the gas exits from the outlet, a high-gas-percentage local space is formed within this small gap, making it difficult for ambient gas to enter, thus achieving effective atmosphere control near the sampling point.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A swirling gas curtain type laser-induced breakdown spectral atmosphere control device, characterized in that, The device includes a housing, an air inlet, a pressure equalization chamber, a jet nozzle, a through tube, and an air outlet; The through tube is disposed inside the housing and is used to provide a laser incident path, and an annular flow channel is formed between the outer wall of the through tube and the inner wall of the housing. The pressure equalization chamber is an annular cavity located inside the housing and is connected to the air inlet for air supply; the air inlet end of the jet nozzle is connected to the pressure equalization chamber, and the air outlet end of the jet nozzle is located inside the annular flow channel, so that gas is injected from the pressure equalization chamber into the annular flow channel through the jet nozzle; The gas outlet is located at the outlet end of the housing and communicates with the annular flow channel, so that the gas forms a continuous airflow around the circumference of the pipe in the annular flow channel and is discharged from the gas outlet, thereby forming a continuous air curtain in the circumference of the outlet area, and achieving effective atmosphere control in the area to be measured.

2. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 1, characterized in that, The outlet includes a contraction section, a short straight section, and an expansion section in sequence along the gas flow direction. The contraction section is used to converge and accelerate the incoming flow from the annular channel, the short straight section is used to rectify and stabilize the flow field, and the expansion section is used to stabilize the outward expansion of the airflow to reduce the entrainment and remixing of ambient gas in the near field of the outlet.

3. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 1, characterized in that, There are two jet holes, which are symmetrically arranged 160-200° apart along the circumference of the pressure equalization chamber. The jet holes are arranged obliquely downward and are 60-120° away from the air inlet in the circumferential direction. The jet holes inject gas into the annular flow channel in an oblique direction, so that the gas forms a rotating flow in the annular flow channel.

4. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 3, characterized in that, In addition to having a horizontal oblique direction, the axis of the jet hole is also inclined downward relative to the cross-sectional plane perpendicular to the housing axis, so that the gas injected into the annular gap flow channel can more easily flow downward along the housing axis and be discharged from the outlet.

5. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 4, characterized in that, The axis of the jet orifice is at a 30-50° angle to the tangent of the inner wall of the pressure equalization chamber, and is inclined downward at a 5-20° angle relative to the section perpendicular to the axis of the housing.

6. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 5, characterized in that, The radius of the jet nozzle is 1.1-1.5 mm.

7. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 6, characterized in that, The flow rate of the gas introduced into the inlet is 1-5 L / min.

8. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 1, characterized in that, The height of the through tube is 30-45mm, and the bottom of the through tube is 8-15mm away from the bottom of the shell.

9. The swirling gas curtain type laser-induced breakdown spectral atmosphere control device according to claim 1, characterized in that, The atmosphere control device is installed directly above the sampling point, with its outlet end maintaining a distance of approximately 2-5 mm from the sample surface.

Images