Adaptive working method of photomultiplier applied to ICP spectrometer

Abstract

This invention discloses an adaptive operating method for a photomultiplier tube (PMT) in an ICP spectrometer, comprising: setting an initial operating voltage and circuit gain of the PMT as initial conditions, and using these initial conditions as a reference; under these initial conditions, acquiring the intensity value of the photoelectric signal obtained by the PMT; setting a maximum intensity value of the photoelectric signal, a minimum operating voltage, and a minimum circuit gain; when the intensity value of the acquired photoelectric signal is greater than the maximum intensity value, adjusting the operating voltage and circuit gain based on the minimum value of the operating voltage and circuit gain until the intensity requirement of the photoelectric signal is met, thus obtaining the adaptive operating conditions; and normalizing the intensity value of the photoelectric signal under the adaptive operating conditions. This invention can automatically determine the PMT operating conditions for different samples, greatly reducing the experience requirements of the instrument for the experimenter and significantly reducing the probability of operator error.

Description

Technical Field

[0001] This invention relates to the field of optical instrument technology, and in particular to an adaptive operating method for a photomultiplier tube used in an ICP spectrometer. Background Technology

[0002] ICP spectrometers are among the most commonly used analytical instruments in the field of elemental analysis. They possess advantages such as strong excitation capability, good stability, high spectral resolution, and a wide wavelength range (from infrared to far-ultraviolet). They offer fast testing speeds and broad wavelength coverage, making them an ideal testing method for material composition analysis. ICP spectrometers are classified into multi-channel simultaneous, single-channel scanning, and full-spectrum direct-reading types. Single-channel scanning ICP spectrometers use a rotating dispersive element (usually a grating) for spectral dispersion and a photomultiplier tube for photoelectric signal detection. Multi-channel simultaneous ICP spectrometers also often use photomultiplier tubes for photoelectric signal detection.

[0003] The workflow of an ICP spectrometer is as follows:

[0004] Peak finding and peak determination: ICP spectrometer is used to establish the test method for the sample to be tested. Based on experience, the experimenter sets the working voltage and circuit gain for the wavelengths corresponding to the elements in the sample to be tested, and then determines the peak position of the wavelength to be tested.

[0005] Plot the working curve; test the standard series samples and plot the working curve.

[0006] Unknown sample testing involves testing unknown samples and calculating the test results using a working curve. The operation of a photomultiplier tube is a prerequisite for ensuring the accuracy of signal detection and data processing during the testing process.

[0007] The detection of photoelectric signals by a photomultiplier tube (PMT) depends on the PMT's operating voltage and the gain of the signal processing circuit, and its operating conditions are closely related to the content of the sample being tested. Currently, the common practice is for the experimenter to assess the element content in the sample and attempt tests based on experience. This not only makes the operation cumbersome but also requires the experimenter to have extensive experience, resulting in high operating costs and low evaluation efficiency. Therefore, there is an urgent need to provide an adaptive operating method for PMTs to solve the problem of determining the PMT's operating conditions for different samples. Summary of the Invention

[0008] The purpose of this invention is to provide an adaptive operating method for photomultiplier tubes used in ICP spectrometers, which can automatically determine the operating conditions of the photomultiplier tube for different samples, greatly reducing the experience requirements of the instrument for the experimenter and significantly reducing the probability of operator error.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] An adaptive operating method for a photomultiplier tube used in an ICP spectrometer, the method comprising the following steps:

[0011] S1, Set initial conditions: Set the initial operating voltage and circuit gain of the photomultiplier tube as initial conditions, and use the initial conditions as a reference;

[0012] S2, Data Acquisition: Under the initial conditions, the intensity value of the photoelectric signal obtained by the photomultiplier tube is acquired;

[0013] S3, Data interpretation and adaptive working conditions: Set the maximum intensity value of the photoelectric signal, the minimum value of the working voltage and the minimum value of the circuit gain. When the intensity value of the photoelectric signal collected in step S2 is greater than the maximum intensity value, adjust the working voltage and the circuit gain based on the minimum value of the working voltage and the circuit gain until the intensity requirement of the photoelectric signal is met, and obtain the adaptive working conditions.

[0014] S4, Normalized Data Processing: Normalizes the intensity values ​​of photoelectric signals under adaptive operating conditions.

[0015] Further, in step S3, when the intensity value of the photoelectric signal acquired in step S2 is greater than the maximum intensity value, the operating voltage and circuit gain are adjusted based on the minimum value of the operating voltage and circuit gain until the intensity requirement of the photoelectric signal is met, thus obtaining adaptive operating conditions, specifically including:

[0016] S301, determine whether the current value of the circuit gain under the initial conditions is greater than the minimum value of the circuit gain. If so, decrease the current value of the circuit gain and collect the intensity value of the photoelectric signal obtained by the photomultiplier tube.

[0017] S302, if not, determine whether the current value of the working voltage under the initial conditions is greater than the minimum value of the working voltage; if so, decrease the current value of the working voltage and collect the intensity value of the photoelectric signal obtained by the photomultiplier tube.

[0018] S303, repeat steps S301-S302 until the intensity value of the acquired photoelectric signal is less than the maximum intensity value, and obtain the final adaptive working conditions.

[0019] Further, in step S4, the intensity value of the photoelectric signal under adaptive operating conditions is normalized, including:

[0020] During the continuous adaptive adjustment of the photomultiplier tube's operating conditions, based on the ratio of circuit gain adjustment and the corresponding relationship of operating voltage amplitude adjustment, the intensity value of the photoelectric signal obtained from the photomultiplier tube under the initial conditions is normalized to the intensity value of the photoelectric signal under the adaptive operating conditions, using the intensity value of the photoelectric signal obtained from the photomultiplier tube under the initial conditions as a benchmark.

[0021] Further, in step S4, based on the ratio of circuit gain adjustment and the corresponding relationship of operating voltage amplitude adjustment, and taking the intensity value of the photoelectric signal obtained by the photomultiplier tube under initial conditions as a benchmark, the intensity value of the photoelectric signal under adaptive operating conditions is normalized, including:

[0022] The photoelectric signal corresponding to the wavelength of the sample element obtained by the acquisition board is obtained by the following formula:

[0023] I = Gain × [I] d +I s ]+I offfset (1)

[0024] In the formula, I represents the photoelectric signal acquired by the acquisition board; Gain represents the circuit gain; I d I is the dark current signal of the photomultiplier tube. s For the actual spectral signal, I offfset This is the circuit board bias signal;

[0025] Operating voltage V and actual spectral signal I s The correspondence between them is as follows:

[0026] I s =A*V kn (2)

[0027] In the formula, A is the inherent parameter of the photomultiplier tube with respect to wavelength; n is the multiplication order of the photomultiplier tube; k is determined by the structure and material of the photomultiplier tube electrodes;

[0028] Based on formulas (1) and (2), I is obtained under different circuit gain conditions. offfset The ratio between the gain and the gain of the circuit is used to obtain the dark current signal I of the photomultiplier tube. d By determining the relationship between k and the operating voltage V, the true value of k can be obtained.

[0029] The normalized formula is shown below:

[0030]

[0031] In the formula, x is the coefficient number of the working voltage, and y is the gain level of the circuit. The normalized spectral photoelectric signal displayed on the host computer; Gain (y0) This is the default circuit gain condition; The dark current signal strength of the photomultiplier tube under default operating conditions; The circuit gain condition under adaptive operating conditions. To determine the dark current signal strength of the photomultiplier tube under adaptive operating conditions, The ratio of the actual spectral signals before and after adaptation; The spectral photoelectric signal obtained under adaptive operating conditions. This is the circuit board bias signal under adaptive circuit gain conditions.

[0032] Furthermore, in step S3, the amplitude interval for adjusting the operating voltage is 10V, and the amplitude interval for adjusting the circuit gain is 1.

[0033] Furthermore, the higher the value of the operating voltage, the higher the intensity of the photoelectric signal; the higher the value of the circuit gain, the higher the intensity of the photoelectric signal.

[0034] Furthermore, the maximum and minimum values ​​of the operating voltage are set according to the hardware specifications of the photomultiplier tube; the maximum and minimum values ​​of the circuit gain are set according to the circuit of the acquisition system as needed.

[0035] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The adaptive operating method for a photomultiplier tube (PMT) applied to an ICP spectrometer provided by the present invention first sets the initial operating voltage and circuit gain of the PMT, using the initial conditions as a reference; secondly, under the initial operating voltage and circuit gain conditions, the PMT obtains the intensity value of the photoelectric signal; then, data interpretation is performed and the operating conditions are adaptively adjusted based on the interpretation results, which is simple and effective; finally, normalized data processing is performed under the adaptive operating conditions. The adaptive operating method provided by the present invention can adaptively optimize the operating voltage and circuit gain, and can efficiently and automatically determine the PMT operating conditions for different samples; the introduction of the adaptive operating method greatly reduces the experience requirements of the experimenter and greatly reduces the probability of experimenter misoperation; the normalized data processing method, based on the actual state of the PMT and starting from the principle, further ensures the accuracy of the data results and improves the performance of the instrument. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0037] Figure 1This is a block diagram of an ICP spectrometer;

[0038] Figure 2 This is a schematic flowchart illustrating the adaptive operation method of the photomultiplier tube in an ICP spectrometer according to the present invention.

[0039] Figure 3 This is a schematic diagram of the data interpretation and adaptive working conditions of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The purpose of this invention is to provide an adaptive operating method for photomultiplier tubes in ICP spectrometers. This method automatically determines the operating conditions of the photomultiplier tube for different samples, greatly reducing the experience requirements of the instrument and significantly decreasing the probability of operator error. For example, the ICP spectrometer is a sequential ICP spectrometer.

[0042] like Figure 1 The diagram shows the structural block diagram of a sequential ICP spectrometer. A sequential ICP spectrometer mainly consists of four parts: a light source, a sample introduction system, a dispersion system, and a detection system. The dispersion system is the key component, and its dispersive element is a scanning grating.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 2 As shown, the adaptive operation method for a photomultiplier tube in an ICP spectrometer provided by this invention includes the following steps:

[0045] S1, Set initial conditions: Set the initial operating voltage and circuit gain of the photomultiplier tube as initial conditions, and use the initial conditions as a reference;

[0046] S2, Data Acquisition: Under the initial conditions, the intensity value I (current) of the photoelectric signal obtained by the photomultiplier tube is acquired;

[0047] S3, Data Interpretation and Adaptive Working Conditions: Set the maximum intensity value I(max) of the photoelectric signal, the minimum value of the operating voltage and the minimum value of the circuit gain. When the intensity value of the photoelectric signal acquired in step S2 is greater than the maximum intensity value, i.e., I(current) ≥ I(max), adjust the operating voltage and the circuit gain based on the minimum value of the operating voltage and the circuit gain until the intensity requirement of the photoelectric signal is met, thus obtaining adaptive working conditions; in addition, if the intensity value of the photoelectric signal acquired in step S2 is less than the maximum intensity value, then the debugging is stopped.

[0048] S4, Normalized Data Processing: Normalizes the intensity values ​​of photoelectric signals under adaptive operating conditions.

[0049] Among them, such as Figure 3 As shown, in step S3, when the intensity value of the photoelectric signal acquired in step S2 is greater than the maximum intensity value, the operating voltage and circuit gain are adjusted based on the minimum value of the operating voltage and circuit gain until the intensity requirement of the photoelectric signal is met, thus obtaining adaptive operating conditions. Specifically, this includes:

[0050] S301, determine whether the current value of the circuit gain under the initial conditions is greater than the minimum value of the circuit gain. If so, decrease the current value of the circuit gain and collect the intensity value of the photoelectric signal obtained by the photomultiplier tube.

[0051] S302, if not, determine whether the current value of the working voltage under the initial conditions is greater than the minimum value of the working voltage. If yes, decrease the current value of the working voltage and collect the intensity value of the photoelectric signal obtained by the photomultiplier tube; if not, stop debugging.

[0052] S303, repeat steps S301-S302 until the intensity value of the acquired photoelectric signal is less than the maximum intensity value, and obtain the final adaptive working conditions.

[0053] In step S4, the intensity value of the photoelectric signal under adaptive operating conditions is normalized, including:

[0054] During the continuous adaptive adjustment of the photomultiplier tube's operating conditions, based on the relationship between the circuit gain adjustment ratio and the amplitude adjustment of the operating voltage, the intensity value of the photoelectric signal obtained from the photomultiplier tube under the initial conditions is normalized to a standard value. Specifically, the normalization data processing procedure is as follows:

[0055] The photoelectric signal corresponding to the wavelength of the sample element obtained by the acquisition board is obtained by the following formula:

[0056] I = Gain × [I] d +I s ]+Iofffset (1)

[0057] In the formula, I represents the photoelectric signal acquired by the acquisition board; Gain represents the circuit gain; I d I is the dark current signal of the photomultiplier tube. s For the actual spectral signal, I offfset This is the circuit board bias signal;

[0058] Operating voltage V and actual spectral signal I s The correspondence between them is as follows:

[0059] I s =A*V kn (2)

[0060] In the formula, A is the inherent parameter of the photomultiplier tube with respect to wavelength; n is the multiplication order of the photomultiplier tube; k is determined by the structure and material of the photomultiplier tube electrodes; for example, n is generally 10, and k is generally between 0.7 and 0.8.

[0061] Based on formulas (1) and (2), I is obtained under different circuit gain conditions. offfset The ratio between the gain and the gain of the circuit is used to obtain the dark current signal I of the photomultiplier tube. d By determining the relationship between k and the operating voltage V, the true value of k can be obtained.

[0062] The normalized formula is shown below:

[0063]

[0064] In the formula, x is the coefficient number of the working voltage, and y is the gain level of the circuit. The normalized spectral photoelectric signal is displayed on the host computer. This is the default circuit gain condition; The dark current signal strength of the photomultiplier tube under default operating conditions; The circuit gain condition under adaptive operating conditions. To determine the dark current signal strength of the photomultiplier tube under adaptive operating conditions, The ratio of the actual spectral signals before and after adaptation; The spectral photoelectric signal obtained under adaptive operating conditions. This is the circuit board bias signal under adaptive circuit gain conditions.

[0065] Among them, (1) I is obtained under different circuit gain conditions. offfset The ratio relationship between the gain and the circuit gain includes the following two steps:

[0066] The first step is to ground the input signal of the photomultiplier tube. At this time, Id =0, I s =0; This is used to obtain the circuit board bias signal I under different circuit gain conditions. offfset The subscript y represents the gain level of the circuit. When the circuit gain is at the y level, it is as shown in the following formula:

[0067] I (y) =I offfset(y) , y=1,2,…,m; (4)

[0068] Obtain the circuit board bias signal under different circuit gain conditions;

[0069] The second step is to set the input signal of the photomultiplier tube to 1μA. At this time:

[0070] I s(1) =I s(2) …=I s(m) (5)

[0071] When the circuit gain is in the y-range:

[0072] I (y) =Gain (y) ×I s(y) +I offfset(y) , y=1,2,…,m; (6)

[0073] From formulas (4) to (6), the ratio between circuit gains can be obtained by the following formula:

[0074]

[0075] In the formula, l = 2, 3, ... m, p = 1, 2, ... l-1;

[0076] If no gain switching occurs during the test, then there is no gain ratio relationship between the two.

[0077] (2) Obtain the dark current signal I of the photomultiplier tube d The specific implementation of the relationship with the operating voltage V is as follows:

[0078] When the spectrometer is not working, no spectral signal enters the optical system, i.e., I s =0, set the operating voltage of the photomultiplier tube as follows:

[0079] V x =x*100, x=1,2,…,10 (8)

[0080] The photoelectric signals obtained by the acquisition board under different circuit gain conditions were tested respectively;

[0081] The photoelectric signals recorded by the acquisition board under different operating voltages and circuit gains are shown below:

[0082] I (x)(y) =Gain (y) *I d(x)(y) +I offfset(y) (9)

[0083] The dark current signal I of the photomultiplier tube under various circuit gain conditions can be obtained from formula (9). d The relationship curve between the operating voltage V and the operating voltage V can be expressed as:

[0084]

[0085] For a given circuit gain, Gain (y) and I offfset(y) It is a fixed value, from which the dark current signal I of the photomultiplier tube can be obtained. d(x)(y) The photoelectric signal I obtained by the acquisition board under different operating voltages (x)(y) The working curve.

[0086] (3) The specific implementation method for obtaining the actual value of k is as follows:

[0087] Taking the Mn element as an example, as specified in GB / T36244-2018 standard, under the condition of the spectrometer operation, the Mn solution is aspirated and sprayed, combined with the obtained I... d(x)(y) The correspondence between the photoelectric signal of the Mn solution and the photomultiplier tube operating conditions was obtained, as shown in the following formula:

[0088]

[0089] By combining equation (2), the least squares solution of k in equation (2) can be obtained;

[0090] In this study, the photoelectric signal of the Mn solution is selected from the unsaturated spectral photoelectric signal. Saturation is defined as the peak intensity at the wavelength corresponding to the analyte being ≥ I(max).

[0091] Assuming the initial operating voltage and circuit gain Under the given conditions, the spectral photoelectric signal of a certain element in the sample to be tested is: If the actual test results are This necessitates adaptive data processing. Let the adaptive operating voltage and circuit gain be respectively... and The photoelectric signal obtained under these working conditions is By normalizing the spectral photoelectric signal using formula (3), the spectral photoelectric signal normalized to the default operating conditions can be obtained.

[0092] In a specific embodiment, the photomultiplier tube used in the experiment was Beijing Hamamatsu R354-01, the maximum operating voltage was set to 1000V, and the maximum circuit gain was set to 3.

[0093] Gain between the obtained circuit gains (2)(1) Gain (3)(2) and Gain (3)(1) The values ​​are 9.57, 9.13, and 87.43 respectively.

[0094] The obtained k is 7.32;

[0095] Using the two values ​​obtained above, combined with formula (3), we can obtain the normalized data after adaptive working conditions.

[0096] The default operating voltage and circuit gain are 800 and 2, respectively. Following the workflow of the ICP spectrometer, the relationship between concentration and photoelectric signal intensity is shown in Table 1. The working curve is: Y = 550138*X + 18230, where X represents the concentration of the test sample, typically in units set by the system, such as ug / mL or %; Y represents the intensity, generally referring to the value of the AD converter, and has no unit.

[0097] Table 1. Correspondence between concentration and photoelectric signal intensity

[0098] Serial Number Concentration (μg / ml) Photoelectric signal strength Standard 1 0 19032.077 Standard 2 0.5 293480.209 Standard 3 1 582551.267 Standard 4 2 1097986.168

[0099] The concentration of the sample to be tested was 15 μg / ml. After adaptation, the operating voltage and circuit gain were 680 and 1, respectively. At this time, the photoelectric signal intensity was 278389.425, and the normalized intensity was 8739272.315. According to the working curve, the normalized concentration was 15.85 μg / ml, which met the deviation range of semi-quantitative analysis.

[0100] In summary, the adaptive operating method for photomultiplier tubes in ICP spectrometers provided by this invention offers a simple and effective basis for adjusting the operating voltage and circuit gain based on data interpretation. The introduction of the adaptive operating method greatly reduces the experience requirements of the experimenter and significantly reduces the probability of operator error. The normalized data processing method, based on the actual state of the photomultiplier tube and starting from the principle, further ensures the accuracy of the data results and improves the performance of the instrument.

[0101] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An adaptive operating method for a photomultiplier tube used in an ICP spectrometer, characterized in that, Includes the following steps: S1, Set initial conditions: Set the initial operating voltage and circuit gain of the photomultiplier tube as initial conditions, and use the initial conditions as a reference; S2, Data Acquisition: Under the initial conditions, the intensity value of the photoelectric signal obtained by the photomultiplier tube is acquired; S3, Data Interpretation and Adaptive Operating Conditions: Set the maximum intensity value of the photoelectric signal, the minimum operating voltage, and the minimum circuit gain. When the intensity value of the photoelectric signal acquired in step S2 is greater than the maximum intensity value, adjust the operating voltage and circuit gain based on the minimum operating voltage and circuit gain until the intensity requirement of the photoelectric signal is met, thus obtaining adaptive operating conditions; specifically including: S301: Determine whether the current value of the circuit gain is greater than the minimum value of the circuit gain. If so, decrease the current value of the circuit gain and acquire the intensity value of the photoelectric signal obtained by the photomultiplier tube. S302, if not, determine whether the current value of the working voltage is greater than the minimum value of the working voltage. If so, decrease the current value of the working voltage and collect the intensity value of the photoelectric signal obtained by the photomultiplier tube. S303, Repeat steps S301-S302 until the intensity value of the collected photoelectric signal is less than the maximum intensity value, and obtain the final adaptive working conditions. S4, Normalized Data Processing: Normalizes the intensity values ​​of photoelectric signals under adaptive operating conditions.

2. The adaptive operating method of a photomultiplier tube applied to an ICP optical spectrometer according to claim 1, characterized in that, In step S4, the intensity value of the photoelectric signal under adaptive operating conditions is normalized, including: During the continuous adaptive adjustment of the photomultiplier tube's operating conditions, based on the ratio of circuit gain adjustment and the corresponding relationship of operating voltage amplitude adjustment, the intensity value of the photoelectric signal obtained from the photomultiplier tube under the initial conditions is normalized to the intensity value of the photoelectric signal under the adaptive operating conditions, using the intensity value of the photoelectric signal obtained from the photomultiplier tube under the initial conditions as a benchmark.

3. The adaptive operating method of a photomultiplier tube applied to an ICP spectrometer according to claim 2, characterized in that, In step S4, based on the ratio of circuit gain adjustment and the corresponding relationship of operating voltage amplitude adjustment, and taking the intensity value of the photoelectric signal obtained by the photomultiplier tube under initial conditions as a benchmark, the intensity value of the photoelectric signal under adaptive operating conditions is normalized, including: The photoelectric signal corresponding to the wavelength of the sample element obtained by the acquisition board is obtained by the following formula: （1） In the formula, The photoelectric signals acquired by the acquisition board; For circuit gain; This is the dark current signal of the photomultiplier tube. This is the actual spectral signal. This is the circuit board bias signal; Operating voltage The correspondence between the actual spectral signal is shown below: （2） In the formula, These are the inherent parameters of the photomultiplier tube with respect to wavelength; The multiplication stage of the photomultiplier tube; It is determined by the structure and material of the photomultiplier tube electrodes; Based on formulas (1) and (2), the gain under different circuit gain conditions is obtained. The ratio between the gain and the circuit gain is used to obtain the dark current signal of the photomultiplier tube. With operating voltage Relationship, to obtain The actual value; The normalized formula is shown below: （3） In the formula, This is the coefficient number for the operating voltage. This refers to the gain setting of the circuit. The normalized spectral photoelectric signal is displayed on the host computer. This is the default circuit gain condition; The dark current signal strength of the photomultiplier tube under default operating conditions; The circuit gain condition under adaptive operating conditions. To determine the dark current signal strength of the photomultiplier tube under adaptive operating conditions, The ratio of the actual spectral signals before and after adaptation; The spectral photoelectric signal obtained under adaptive operating conditions. This is the circuit board bias signal under adaptive circuit gain conditions.

4. The adaptive operating method for a photomultiplier tube applied to an ICP spectrometer according to claim 1, characterized in that, In step S3, the amplitude interval for adjusting the operating voltage is 10V, and the amplitude interval for adjusting the circuit gain is 1.

5. The adaptive operating method for a photomultiplier tube applied to an ICP spectrometer according to claim 1, characterized in that, The higher the operating voltage, the stronger the photoelectric signal; the higher the circuit gain, the stronger the photoelectric signal.

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