Airtightness in-situ detection method for detector interface in ICP-OES system

Abstract

The invention relates to the field of airtightness detection, in particular to an in-situ airtightness detection method for a detector interface in an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) system, which comprises the following steps of: controlling a DMD (Digital Micromirror Device) micromirror array to be switched between a fully-open state and a fully-closed state in a carrier gas stable stage when the ICP-OES system ignites plasma torch flame and no sample is fed; respectively recording photon counting values of the MCP single photon counting detector when the DMD micromirror array is in two states, and taking a difference value of the photon counting values in the two states as an effective luminous flux reference; and periodically measuring a photon number difference value, calculating an attenuation rate according to the photon number difference value, and when the attenuation rate exceeds a preset threshold value, judging that the air tightness of the interface is abnormal. The method solves the problems of offline, qualitative and lagged pain points in the prior art, guarantees the detection precision and operation stability of the ICP-OES system, and reduces the operation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of air tightness detection, and particularly relates to an air tightness in-situ detection method for a detector interface in an ICP-OES system. BACKGROUND

[0002] Inductively coupled plasma atomic emission spectrometer (ICP-OES) as a core means of trace analysis of inorganic elements plays a crucial role in the fields of environmental monitoring, food safety, geological exploration and material science. Its working principle is to gasify and excite atoms of sample solution through a high-temperature plasma torch maintained by argon, and to realize quantitative analysis by measuring the emission intensity of element characteristic spectrum. With the increasing requirements of analytical science on detection sensitivity, dynamic range and long-term stability of the instrument, the performance of the detection system has become one of the key factors restricting the development of ICP-OES technology.

[0003] Traditional ICP-OES systems generally use deep-cooled charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) image sensors based on semiconductor technology as spectral detectors. Such detectors need to work in a deep cooling (usually below -70°C) environment to suppress dark current noise. However, in the deep ultraviolet band (especially below 200 nm), due to the intrinsic absorption effect of semiconductor materials, the quantum efficiency decays sharply, resulting in limited detection capability of the system in this important spectral region and narrow dynamic range.

[0004] To break through the above bottleneck, in recent years, a new type of detection architecture combining micro-channel plate (MCP) single-photon counting imaging detector and digital micro-mirror device (DMD) spatial light modulator has emerged. MCP detector has extremely high sensitivity and dynamic range, and can realize extremely low dark count rate (such as below 0.5 counts / (s·cm 2 ) ) at room temperature without complex deep cooling system. DMD as a programmable digital spatial grating can realize selective passing or blocking of specific spectral components through rapid flipping of micro-mirror array. The two work together to build an innovative model of "cold optics + room temperature detection", which can avoid the inherent defects of deep-cooled detectors in principle and is expected to significantly improve the performance of the system in the ultraviolet band.

[0005] However, when such high-performance UV imaging detectors (e.g. DMD-MCP system) are integrated into existing ICP-OES systems, serious technical adaptation challenges are encountered. The original system is usually designed with a highly integrated interface that matches a specific vendor's (e.g. E2V, UK) cryogenic camera, with the mechanical coaxiality, vacuum sealing level, and focusing mechanism being coupled with each other. The new detector, due to the introduction of DMD light path folding and the corresponding coupling optical system, has significantly increased physical size and structural complexity (volume increase can exceed 400%), which cannot be directly compatible with the original interface. The mismatch of the interface makes it extremely difficult to seal, and it is difficult to achieve complete sealing, resulting in continuous leakage of a small amount of argon during system operation.

[0006] This micro-leakage is usually discovered and located by offline helium mass spectrometry leak detection in the traditional maintenance mode, which is usually quarterly or annual. However, there is a lack of effective in-situ monitoring means during the online operation of the ICP-OES system. Argon leakage will cause instability of the plasma torch flame chamber pressure and introduce impurity gases such as oxygen and water vapor in the air. Oxygen has strong absorption characteristics in the deep ultraviolet region below 190 nm, and even a small amount of oxygen will cause the spectral signal intensity in this wavelength band to decay. At the same time, the introduction of impurity gases will change the impedance and stability of the plasma, causing the torch flame to drift, the signal-to-noise ratio to decrease, and the analysis results to be less reproducible. In order to temporarily suppress the effects of leakage, the current engineering solution is often forced to use a continuous high flow of argon for purging (e.g. increasing the purge flow from the conventional 1 L / min to 5 L / min). Although this method can dilute the leaked gas, it has significant drawbacks: first, the argon consumption is doubled, significantly increasing the operating cost; second, the thermal disturbance and turbulent noise introduced by the high flow of gas will exacerbate the baseline drift; third, the increased load on the vacuum exhaust system may frequently trigger safety interlocks, causing unplanned downtime, affecting equipment availability and analysis efficiency.

[0007] Therefore, in view of the interface air tightness monitoring problem in the integration of the new DMD-MCP ultraviolet imaging detector and the ICP-OES system, it is urgent to develop an in-situ detection method for the interface air tightness that can be monitored online in real time without disturbing the normal analysis, without the need for additional complex sensors, and can be quantitatively evaluated to ensure the stable performance of the instrument and reduce the operating and maintenance costs. SUMMARY

[0008] Therefore, in view of the interface air tightness monitoring problem in the integration of the new DMD-MCP ultraviolet imaging detector and the ICP-OES system, it is urgent to develop an in-situ detection method for the interface air tightness that can be monitored online in real time without disturbing the normal analysis, without the need for additional complex sensors, and can be quantitatively evaluated to ensure the stable performance of the instrument and reduce the operating and maintenance costs.

[0009] To achieve the above objectives, the technical solution created by this invention is implemented as follows: An in-situ method for airtightness testing of a detector interface in an ICP-OES system includes the following steps: S1: During the carrier gas stabilization phase when the plasma torch is ignited in the ICP-OES system and no sample is introduced, control the DMD micromirror array to switch between fully open and fully closed states. S2: Record the photon count N collected by the MCP single-photon counting detector when the DMD micromirror array is fully open. open And the dark count N acquired when the DMD micromirror array was in the fully off state. close Count the number of photons N open With dark count N close The photon number difference ΔN is used as the effective luminous flux reference. S3: Periodically measure the photon number difference ΔN, and calculate the attenuation rate η based on the photon number difference ΔN. When the attenuation rate η exceeds a preset threshold, the interface airtightness of the DMD-MCP ultraviolet imaging detector is determined to be abnormal. The formula for calculating the attenuation rate η is η=(ΔN0-ΔN). t ) / ΔN0×100%, where ΔN0 represents the initial reference photon number difference, ΔN t This represents the difference in the number of photons obtained from the t-th monitoring.

[0010] Furthermore, the initial reference photon number difference ΔN0 is calculated as follows: Based on multiple measurements, a photon number difference sequence {ΔN1, ΔN2, ..., ΔN} was obtained. t}, take the photon number difference sequence {ΔN1, ΔN2, ..., ΔN t The arithmetic mean of the values ​​is used as the initial reference photon number difference ΔN0.

[0011] Furthermore, before each measurement of the photon number difference ΔN, image data of the DMD micromirror array in a fully off state for a preset number of frames is acquired to obtain an image dataset, and the average dark count N of the image dataset is calculated. close_base This serves as the baseline for the current measurement cycle; when measuring the photon number difference ΔN, the collected dark count N will be used as the baseline. close With average dark count N close_base Subtract to obtain the dark count after deducting baseline drift, then add the collected photon count N. open Subtracting the dark count after deducting baseline drift yields the photon number difference ΔN.

[0012] Furthermore, following step S3, the following steps are also included: S4: Through a standard argon concentration calibration experiment, a quantitative relationship Q=k·η between the attenuation rate η and the equivalent air leakage rate Q is established in advance, wherein k is a calibration coefficient; S5: In actual operation of the ICP-OES system, the real-time measured attenuation rate η is substituted into the quantitative relationship Q=k·η, the equivalent air leakage rate Q is calculated, and a graded alarm is given according to the numerical range of the equivalent air leakage rate Q.

[0013] Further, the calculation method of the calibration coefficient k is as follows: Different known purity argon is used as a carrier gas, and the corresponding attenuation rate η is measured under the standard working condition of the ICP-OES system. According to the equivalent air leakage rate Q corresponding to each known purity argon and the measured attenuation rate η, the calibration coefficient k is determined by linear fitting of the two.

[0014] Further, the graded alarm mechanism is as follows: When Q When a≤Q When Q≥b, a high-level warning is triggered, and the operation of the ICP-OES system is stopped. Wherein, a and b are threshold values set according to the noise level and detection accuracy requirements of the ICP-OES system, and b>a.

[0015] Compared with the prior art, the present application can achieve the following beneficial effects: 1. The present application does not need to stop and introduce external tracer gas, and directly uses the light source and detector of the ICP-OES system to complete the interface airtightness detection during the normal operation of the ICP-OES system.

[0016] 2. The present application uses the photon counting difference ΔN generated by DMD modulation as a detection parameter, which is extremely sensitive to the concentration change of light-absorbing impurity gas (such as oxygen) in the optical path. Based on the Beer-Lambert law, the present application can detect the change of the concentration of light-absorbing impurity gas caused by slight leakage, and its sensitivity is much higher than that of the traditional pressure attenuation method, and it is especially suitable for airtightness detection of DMD-MCP ultraviolet imaging detector interface, which provides a key technical guarantee for the normal operation of the ICP-OES system.

[0017] 3、The application quantitatively correlates the decay rate η obtained by monitoring with the equivalent air leakage rate Q through pre-calibration, which enables the ICP-OES system not only to alarm whether there is leakage, but also to accurately assess the degree of leakage, and accordingly to realize graded early warning. This provides a scientific basis for predictive maintenance, and users can reasonably arrange maintenance time according to the quantitative results, avoiding excessive maintenance or untimely maintenance, and significantly improving the fine and intelligent level of equipment management.

[0018] 4、Through real-time interface airtightness monitoring, the application enables the ICP-OES system to no longer rely on continuous high-flow argon purge to cover up the leakage problem. Actual measurement and application show that a single set of ICP-OES system can reduce argon consumption by more than 60%, and annual operating cost can save 20-30 thousand yuan RMB. At the same time, it reduces the analysis interruption caused by blind maintenance and unscheduled downtime, improves the equipment availability, and reduces the wear of components such as vacuum pumps, with outstanding comprehensive economic benefits.

[0019] 5、The application does not need to add any additional gas sensor or detection hardware, completely reuses the existing DMD and MCP detectors of the ICP-OES system as sensing units, and realizes new functions only through software algorithm innovation. This scheme does not change the core optical machine structure, does not introduce new failure points, has low implementation cost, high stability, and is very convenient for upgrading and modification on existing spectral instruments equipped with DMD-MCP detectors, and has wide applicability and good popularization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings, and their description, are used to explain the application and are not intended to limit the application. In the drawings: Figure 1 Flowchart of the method for in-situ detection of the airtightness of the detector interface of the ICP-OES system described in the embodiments of the application; Figure 2 Schematic diagram of the curve of ΔN changing with time in the case of argon leakage described in the embodiments of the application; Figure 3 Schematic diagram of linear fitting between the decay rate η and the equivalent air leakage rate Q described in the embodiments of the application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and do not constitute a limitation on the application.

[0022] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0023] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0024] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "assembly", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0026] The present application proposes a method for detecting the gas tightness of the detector interface in an ICP-OES system, the core principle of which is that when the DMD micromirror array is in two extreme states of full opening and full closing under the pure carrier gas working mode with the sample carrier gas turned off, the difference ΔN of the number of photons collected by the MCP single-photon counting detector is only related to the intrinsic emission intensity of argon plasma. According to the Beer-Lambert law, when the argon concentration in the optical path is constant and there is no invasion of absorbing impurity gas, ΔN should remain stable for a long time. When the argon leakage rate is constant, the oxygen concentration c(t) in the chamber rises linearly with time, and according to the Beer-Lambert law, the absorbance A = σ·L·c(t) also rises linearly with time, σ represents the molar absorption coefficient, and L represents the optical path length. Therefore, ΔN(t) = ΔN0·e^( L·t) (L is a constant), that is, ΔN decays exponentially with time t, and the curve of the change of ΔN with time is as shown in Figure 1 .

[0027] Therefore, by periodically repeating the measurement of ΔN and calculating the moving average, an initial reference value ΔN0 is established, and if the subsequent monitoring value ΔN t deviates from ΔN0 (i.e. ΔN t exceeds a preset threshold (such as 3%), it can be determined that the DMD-MCP ultraviolet imaging detector (composed of a DMD micromirror array and a MCP single photon counting detector) interface airtightness is deteriorated and a warning is triggered, thereby realizing in-situ detection of the DMD-MCP ultraviolet imaging detector interface airtightness. In an embodiment, "ΔN decreases by 5% relative to the initial value" is taken as an example threshold for airtightness warning. This value is derived from the theoretical estimation of the application example above and is only used to demonstrate the principles of the invention; in actual application, users should establish a threshold value specific to the instrument after installation, without samples. In the above example, a change of 3% in the ΔN value corresponds to a change of 1.05 x 10 -2 , which is about 9 times the equivalent noise absorbance (NEA = 1.5 x 10 -3 ) of the instrument, at which point the instrument will not be able to accurately detect.

[0028] The process of the method for in-situ detection of the airtightness of the detector interface in the ICP-OES system will be described in detail below.

[0029] As shown in Figure 2 , the method for in-situ detection of the airtightness of the detector interface in the ICP-OES system comprises the following steps: S1: In the ICP-OES system, ignite the plasma torch flame and control the DMD micromirror array to switch between the fully open state and the fully closed state during the stable stage of the carrier gas without sample introduction.

[0030] DMD (Digital Micromirror Device) as a programmable spatial light modulator, its micromirror array can flip between two main working postures at a very high speed. In the fully open state, all effective micromirrors are in the direction of reflecting the incident light to the detection light path, so that the ultraviolet continuous spectrum light emitted by the plasma torch flame is projected as completely as possible to the MCP single photon counting detector; in the fully closed state, the micromirror array is flipped as a whole to the direction of guiding the incident light to the light trap, almost all light flux is absorbed, only a small amount of stray light may reach the MCP single photon counting detector.

[0031] In an embodiment, the switching period is set to 60 to 120 seconds for each fully open collection of the DMD micromirror array, and then immediately switched to the fully closed state and kept for the same length of time, forming a complete differential measurement period. The switching action itself takes very short time, usually in the order of 50 microseconds, which can be ignored in the collection integration time.

[0032] It should be noted that step S1 requires that the plasma torch flame has reached a thermodynamic steady state, i.e. the radio frequency power, the carrier gas flow rate, and the auxiliary gas flow rate are kept constant for at least 5 minutes or more, and no solid or liquid sample is introduced into the plasma region by a peristaltic pump or an atomizer. At this time, the light emitted by the plasma torch flame is mainly the intrinsic continuous background radiation of the high-purity argon plasma and the characteristic spectrum lines of trace impurity elements.

[0033] S2: record the photon counts N collected by the MCP single-photon counting detector when the DMD micromirror array is in the fully open state open and the dark counts N collected by the MCP single-photon counting detector when the DMD micromirror array is in the fully closed state close , respectively. open close The difference ΔN = N - N between the photon counts N and the dark counts N is taken as the effective light flux reference. open close

[0034] The MCP single-photon counting detector uses a combination of microchannel plate gain and position-sensitive anode readout, which can count each ultraviolet photon event that reaches its effective area and give spatial position information. In the present application, only the total count rate is generally used without considering the spatial distribution information, i.e. the total counts of all effective pixels in the entire effective detection region within the integration time period are accumulated to obtain the total count.

[0035] In one possible implementation, to improve the measurement accuracy, the collection time of the DMD micromirror array in each fully open state or fully closed state is not less than 60 seconds, and is preferably 90 seconds to 120 seconds, so as to ensure that the number of photons accumulated in a single measurement period is sufficient, thereby controlling the statistical fluctuation relative error at a low level. For example, under the typical working condition of a plasma power of 1.2 kilowatts and an argon total flow rate of 15 liters per minute, a single integration time of 100 seconds in the fully open state can accumulate about 1100 to 1200 counts, while in the fully closed state, the main is the background dark count of the detector, which is usually only 2 to 5 counts, so the difference ΔN between the photon counts has a high signal-to-noise ratio.

[0036] It can be understood that the difference ΔN between the photon counts essentially represents the pure argon plasma photon flux that can effectively pass through the optical system of the ICP-OES system and finally reach the MCP single-photon counting detector under the current optical path geometry configuration, plasma excitation condition, and argon purity condition. This value is extremely sensitive to the concentration of absorbing gas in the optical path and is the core observation physical quantity for subsequent airtightness detection.

[0037] To reduce the interference of the dark count rate drift of the MCP single-photon counting detector with time on the measurement of ΔN, the following operations are performed before each measurement of ΔN:​​​ Firstly, image data of the DMD micromirror array in the full-off state is collected for a preset number of frames to obtain an image data set, and the average dark count N close_base of the image data set is calculated as the baseline of the current measurement period.

[0038] For example, 5 frames of image data in the full-off state, each with an integration time of 10 seconds, the average dark count N close_base of the 5 frames of image data is calculated as the baseline of the dark count of the current measurement period.

[0039] Subsequently, when measuring ΔN, the collected dark count N close is subtracted from the average dark count N close_base to obtain the dark count after deducting the baseline drift, and the collected photon count N open is subtracted from the dark count after deducting the baseline drift to obtain a more accurate photon number difference ΔN0.

[0040] The present application eliminates the effects of aging of the MCP single-photon counting detector by dynamically updating the baseline of the dark count. The update frequency of the baseline can be adjusted according to the running time of the ICP-OES system and the service life of the MCP single-photon counting detector. For example, at the beginning of the operation of the ICP-OES system, the performance of the MCP single-photon counting detector is relatively stable, and the baseline can be updated once every 3 days; while after the ICP-OES system has been running for more than 6 months, the aging effect of the MCP single-photon counting detector gradually appears, and the baseline can be updated once a day to ensure the long-term stability of the ΔN measurement.

[0041] S3: periodically measure the photon number difference ΔN, and calculate the decay rate η according to the photon number difference ΔN, when the decay rate η exceeds a preset threshold, it is determined that the interface airtightness of the DMD-MCP ultraviolet imaging detector is abnormal.

[0042] A sequence of photon number differences {ΔN0, ΔN1, ΔN2,..., ΔN t} varying with time is established, and a sliding average algorithm is used to extract the trend item, when the decay rate η of the photon number difference ΔN t obtained by the tth monitoring with respect to the initial reference photon number difference ΔN0 exceeds a preset threshold (such as 5%), it is determined that the interface airtightness of the DMD-MCP ultraviolet imaging detector is abnormal.

[0043] The calculation formula of the decay rate η is: η=(ΔN0-ΔN t ) / ΔN0×100%.

[0044] The calculation method of the initial reference photon number difference ΔN0 is: Based on the sequence of photon number differences {ΔN1, ΔN2,..., ΔNt} as the initial reference photon number difference ΔN0. t} as the initial reference photon number difference ΔN0.

[0045] For example: within the first three days after the installation and debugging of the ICP-OES system, perform three complete differential measurement cycles at fixed time periods (such as 10:00 am) each day; each cycle includes three sub-stages of DMD micro-mirror array full-on 100 s → full-off 100 s → full-on 100 s, receiving corresponding photon counts and dark counts on the MCP single-photon counting detector, single acquisition integration time 100 s, calculating single ΔN, obtaining three ΔN single measurement values, then performing arithmetic averaging on the total of nine measurement results over the three days, and the obtained mean value is taken as the initial reference photon number difference ΔN0for long-term monitoring.

[0046] In the actual long-term operation of the ICP-OES system, a rapid diagnosis program is automatically triggered once a day, which is usually performed during the night unattended period or before daily routine maintenance, and the acquisition period can be appropriately shortened to DMD micro-mirror array full-on 60 s + full-off 60 s to reduce the occupied time for normal analysis work. Immediately after each rapid diagnosis, the current ΔN t is calculated, and the current decay rate η t = (ΔN0- ΔN t ) / ΔN0× 100% is further obtained.

[0047] At this point, the core processes of data acquisition, photon count difference calculation, and online monitoring in the DMD-MCP ultraviolet imaging detector interface airtightness in-situ detection method are completed, and subsequent quantitative evaluation of the leakage degree, early warning classification, and establishment of the calibration relationship will be further described.

[0048] After step S3, the following steps are further included: S4: Through a standard argon concentration calibration experiment, a quantitative relationship Q = k·η between the decay rate η and the equivalent air leakage rate Q is established in advance, where k is a calibration coefficient.

[0049] The calculation method of the calibration coefficient k is as follows: Use different known purity argon as carrier gas, measure the corresponding decay rate η under the standard working condition of the ICP-OES system; According to the equivalent air leakage rate Q corresponding to each known purity argon and the measured decay rate η, the calibration coefficient k is determined by linear fitting of the two.

[0050] A quantitative correspondence between the attenuation rate η and the equivalent air leakage rate Q is established through a pre-calibration experiment, so that the leakage degree of argon can be calculated according to the real-time measured attenuation rate η in the actual operation of the ICP-OES system.

[0051] The calibration experiment needs to be performed after the instrument installation and debugging are completed and before the formal analysis task is put into operation, with the purpose of determining the linear or approximate linear relationship between the attenuation rate η and the equivalent air leakage rate Q. During the experiment, a series of argon gases with known purity are used as carrier gas, and the proportion of air impurities in them is gradually changed to simulate different degrees of leakage. Each experiment is performed under standard conditions, that is, the inductively coupled plasma torch flame power is kept at 1.2 kW, the total argon flow rate is 15 liters per minute, the auxiliary gas flow rate is 0.5 liters per minute, and the torch flame stabilization time is not less than 5 minutes.

[0052] In one embodiment, at least 8 different argon concentration points are selected, for example, the purities are 100%, 99.8%, 99.5%, 99.2%, 99.0%, 98.5%, 98.0% and 97.0%, and the corresponding equivalent air leakage rates Q are 0%, 0.2%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0% and 3.0%, respectively. The linear fitting result between the attenuation rate η and the equivalent air leakage rate Q is shown in Figure 3 For each concentration point, 3 complete differential measurement cycles are performed, each cycle including 100 seconds of full-on and 100 seconds of full-off of the DMD micro-mirror array, the ΔN value of each cycle is calculated and the average value is taken, and then the attenuation rate η corresponding to the concentration point is obtained. Finally, by linear fitting method, the calibration coefficient k between the attenuation rate η and the equivalent air leakage rate Q is determined, so that they satisfy the approximate relationship Q=k·η.

[0053] For example, among the above concentration points, when the purity of argon is 99.5%, the equivalent air leakage rate Q is 0.5%, and the measured attenuation rate η is about 0.577%. Through fitting analysis of all concentration point data, the specific value of the calibration coefficient k can be obtained. This coefficient is closely related to the instrument inherent parameters such as optical path length, detector sensitivity and cavity volume, and usually has slight differences among different instrument individuals.

[0054] It should be noted that the calibration experiment should be performed in a laboratory environment with no sample injection and stable environmental conditions to ensure that the measurement results are not disturbed by external interference. The purity of argon used in the experiment needs to be verified by an independent gas analysis instrument to ensure the accuracy of the calibration data. In addition, the calibration result should be reviewed regularly, especially after the instrument undergoes major maintenance or the interface components are replaced, the calibration process needs to be performed again to update the calibration coefficient.

[0055] S5: In the actual operation of the ICP-OES system, the decay rate η measured in real time is substituted into the quantitative relationship Q = k · η to calculate the equivalent air leakage rate Q, and an alarm is triggered according to the numerical range of the equivalent air leakage rate Q.

[0056] After each rapid diagnostic procedure is completed, the system automatically calculates the current decay rate η t and, using the calibration coefficient k determined in step S4, calculates the current decay rate η t and the corresponding equivalent air leakage rate Q t = k · η t . Subsequently, according to the specific value of Q t , the leakage degree is divided into different levels, and the corresponding alarm mechanism is triggered. The threshold for the graded alarm is set based on the noise level of the ICP-OES system measurement accuracy and the requirement for data reliability in actual application.

[0057] The graded alarm mechanism is as follows: When Q t < a, a low-level warning is triggered, allowing the ICP-OES system to continue high-sensitivity analysis; When a ≤ Q t < b, a medium-level warning is triggered, limiting the ICP-OES system to high-sensitivity analysis; When Q t ≥ b, a high-level warning is triggered, stopping the operation of the ICP-OES system; wherein a and b are threshold values set according to the noise level of the ICP-OES system and the detection accuracy requirement, and b > a.

[0058] For example: Set the threshold value a of the low-level warning to 0.863%, when Q t is less than 0.863%, the current decay rate η is about 1.0%, and the signal decay amplitude is about 3 times the instrument noise level, which is still within the measurement error range, allowing the ICP-OES system to continue to perform high-sensitivity analysis tasks.

[0059] Set the threshold values a and b of the medium-level warning to 0.863% and 2.58% respectively, when Q t is between 0.863% and 2.58%, the current decay rate η is about 1.0% to 3.0%, and the signal decay amplitude reaches 3 to 9 times the instrument noise level, the measurement accuracy decreases, and the ICP-OES system will issue a warning to limit high-sensitivity analysis tasks, suggesting that the user avoid performing trace element detection.

[0060] Set the threshold value b of the high-level warning to 2.58%, when Q tWhen the current decay rate η is greater than or equal to 2.58%, the signal attenuation amplitude has exceeded 9 times of the instrument noise level, and the data reliability cannot be guaranteed. The ICP-OES system will immediately trigger the stop and leak detection instruction, and lock the sample injection function to prevent further operation from causing equipment damage or data distortion.

[0061] Preferably, the alarm information will prompt the user through the instrument control panel with different colors and sounds, for example, a low-level warning displays a yellow icon and is accompanied by a short prompt sound, a medium-level warning displays an orange icon and is accompanied by an intermittent prompt sound, and a high-level warning displays a red icon and is accompanied by a continuous alarm sound. At the same time, the system will automatically record the occurrence time, decay rate value, and equivalent leakage rate of each alarm, facilitating subsequent maintenance personnel to trace the root cause of the problem.

[0062] For different levels of leakage alarms, corresponding processing measures are taken to protect the instrument and restore the airtightness.

[0063] Specifically, when a low-level warning is triggered, the system allows continuous operation, but suggests that the user check the sealing components of the interface, such as O-rings, gaskets, or the tightening status of connecting bolts, during the next routine maintenance, and records the current operating parameters for subsequent comparative analysis. When a medium-level warning is triggered, the system will limit high-sensitivity analysis tasks and only allow the execution of element detection within the normal concentration range, while suggesting that the user arrange a special check of the interface airtightness as soon as possible, and temporarily increase the argon purge flow to 2 liters per minute if necessary, to slow down the impact of leaked gas on the signal.

[0064] When a high-level warning is triggered, the system will immediately execute a protective shutdown program, first shutting down the sample injection pump and the atomizer, gradually reducing the radio frequency power to standby state, and then cutting off the torch ignition power to ensure that the plasma is extinguished before entering the safety mode. At the same time, the system will lock all analysis functions until the maintenance personnel complete the leak detection and repair work and manually reset the alarm state. During the shutdown period, it is recommended that the maintenance personnel use a portable gas detection device to conduct a preliminary investigation around the interface, focusing on checking the sealing condition of the connection between the digital micromirror device and the coupling optical system, and disassembling and replacing damaged sealing elements if necessary.

[0065] For example, in a certain actual operation, the system triggered a three-level emergency alarm on the 30th day of operation, with a measured decay rate η of 3.2%, corresponding to an equivalent leakage rate Q t of 2.77%. The maintenance personnel immediately executed the shutdown program, and found a small crack at the interface flange connection that caused a sealing failure. After replacing the new gasket and re-tightening the bolts, the system returned to normal operation, with the decay rate η reduced to below 0.5%, re-entering the safe operating range.

[0066] The present application changes the conventional standby continuous purging mode to small flow purging, for example, the original standby purging flow is 2L / min, according to 300h of purging work per year, 36000L of argon is obtained, according to the unit price of 1.25 yuan / L, 45000 yuan needs to be spent, the purging flow of the present application can be reduced to 0.5L / min, more than 70% of argon can be reduced, and the annual operation cost is greatly reduced.

[0067] In addition to realizing the interface airtightness monitoring, the present application can also utilize the differential measurement data to assist in diagnosing the running state of other key components of the instrument. For example, by long-term monitoring of the change trend of the photon count N open in the fully open state, the transmittance decay of the window lens, mirror and other optical elements in the deep ultraviolet light path can be reflected. When N open drops by more than 10% relative to the initial value, the system will prompt the user to check whether there is pollution or aging phenomenon on the surface of the optical element, and clean or replace it if necessary, so as to avoid systematic deviation of the quantitative analysis result.

[0068] In one embodiment, the stability of the plasma torch flame can also be evaluated by analyzing the fluctuation amplitude of ΔN in a short time. For example, the standard deviation of ΔN in the last 10 times of rapid diagnosis is calculated, and if the value significantly increases, for example, more than 5% of the initial reference value, it may indicate that the torch flame has problems such as turbulence, poor impedance matching or contamination of the inner wall of the quartz torch tube. At this time, the system will suggest the user to check the output stability of the radio frequency power supply, whether the carrier gas flow control valve is normal, or to clean and maintain the torch tube.

[0069] For example, in a certain operation, the system detected that the standard deviation of ΔN increased from the initial 2.5 counts / s to 6.8 counts / s for 3 consecutive days, and combined with the analysis of other operating parameters, it was confirmed that the slight blockage of the auxiliary gas flow control valve caused the unstable flame shape. The user then cleaned the valve and adjusted the flow to the standard value of 0.5 liters per minute, and the fluctuation amplitude of ΔN returned to the normal range, and the accuracy of the instrument analysis was maintained.

[0070] In another embodiment, it can also be extended to real-time monitoring of the purity of high-purity carrier gases such as argon, helium and nitrogen. The gas pipeline accesses a spectral pure reference sample (such as a mercury lamp), measures the intensity of the characteristic spectral line, and detects the concentration of impurity gases (O2, H2O, CO2) in the carrier gas using the same principle. It is suitable for instruments and systems that require ultra-high purity carrier gas, such as gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma mass spectrometry (ICP-MS).

[0071] It should be noted that the above-mentioned extended functions make full use of the multi-dimensional information contained in the differential measurement data, and are not limited to air tightness judgment, but can also provide support for long-term monitoring of the overall performance of the instrument. By regularly recording and analyzing the trend data of N open , N close and ΔN, the user can discover potential problems in advance and take preventive maintenance measures, thereby prolonging the service life of the instrument and ensuring data quality.

[0072] It should be understood that the various forms of flow shown above can be used to reorder, add or delete steps. For example, the steps described in the present disclosure can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, which is not limited herein.

[0073] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for in-situ testing the airtightness of a detector interface in an ICP-OES system, characterized in that, It includes the following steps: S1: During the carrier gas stabilization stage when the plasma torch flame is ignited and no sample is injected in the ICP-OES system, control the DMD micro-mirror array to switch between the fully open state and the fully closed state; S2: Record the photon count N collected by the MCP single-photon counting detector when the DMD micromirror array is fully open. open And the dark count N acquired when the DMD micromirror array was in the fully off state. close Count the number of photons N open With dark count N close The photon number difference ΔN is used as the effective luminous flux reference. S3: Periodically measure the photon number difference ΔN, and calculate the attenuation rate η based on the photon number difference ΔN. When the attenuation rate η exceeds a preset threshold, the interface airtightness of the DMD-MCP ultraviolet imaging detector is determined to be abnormal. The formula for calculating the attenuation rate η is η=(ΔN0-ΔN). t ) / ΔN0×100%, where ΔN0 represents the initial reference photon number difference, ΔN t This represents the difference in the number of photons obtained from the t-th monitoring.

2. The in-situ airtightness detection method for the detector interface in the ICP-OES system according to claim 1, characterized in that, The calculation method of the initial reference photon number difference ΔN0 is as follows: Based on multiple measurements, a photon number difference sequence {ΔN1, ΔN2, ..., ΔN} was obtained. t }, take the photon number difference sequence {ΔN1, ΔN2, ..., ΔN t The arithmetic mean of the values ​​is used as the initial reference photon number difference ΔN0.

3. The in-situ airtightness detection method for the detector interface in the ICP-OES system according to claim 1, characterized in that, Before each measurement of the photon number difference ΔN, image data of the DMD micromirror array in a fully off state for a preset number of frames is acquired to obtain an image dataset. The average dark count N of the image dataset is then calculated. close_base This serves as the baseline for the current measurement cycle; when measuring the photon number difference ΔN, the collected dark count N will be used as the baseline. close With average dark count N close_base Subtract to obtain the dark count after deducting baseline drift, then add the collected photon count N. open Subtracting the dark count after deducting baseline drift yields the photon number difference ΔN.

4. The in-situ airtightness detection method for the detector interface in the ICP-OES system according to claim 3, characterized in that, After step S3, the following steps are further included: S4: Through a standard argon concentration calibration experiment, pre-establish the quantitative relationship Q = k·η between the attenuation rate η and the equivalent air leakage rate Q, where k is the calibration coefficient; S5: During the actual operation of the ICP-OES system, substitute the measured attenuation rate η into the quantitative relationship Q = k·η, calculate the equivalent air leakage rate Q, and perform hierarchical alarm according to the numerical range of the equivalent air leakage rate Q.

5. The in-situ airtightness detection method for the detector interface in the ICP-OES system according to claim 4, characterized in that, The calculation method of the calibration coefficient k is as follows: Use argon with different known purities as the carrier gas, and measure the corresponding attenuation rate η respectively under the standard working conditions of the ICP-OES system; According to the equivalent air leakage rate Q and the measured attenuation rate η corresponding to each known purity of argon, determine the calibration coefficient k by performing linear fitting on the two.

6. The in-situ airtightness detection method for the detector interface in the ICP-OES system according to claim 4, characterized in that, The hierarchical alarm mechanism is as follows: When Q < a, trigger a low-level warning, and allow the ICP-OES system to continue high-sensitivity analysis; When a ≤ Q < b, trigger a medium-level warning, and limit the ICP-OES system to perform high-sensitivity analysis; When Q ≥ b, trigger a high-level warning, and stop the operation of the ICP-OES system; Where a and b are thresholds set according to the noise level and detection accuracy requirements of the ICP-OES system, and b > a.

Images