JP2010107261A - Fluorescent x-ray analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an unnecessary energy-calibration operation, while avoiding an operation of a measurement with poor reliability under a significant energy position gap, by securely informing an analyst that an energy calibration is necessary. <P>SOLUTION: On an X-ray spectrum generated based on a detected signal obtained by irradiating with a primary X-ray a sample 2 to be measured, a Rayleigh scattering ray detection section 14 detects a Rayleigh scattering ray which is expected to appear on an energy position in accordance with a target element of an X-ray tube 1. An energy determination section 15 determines absence of an energy position gap when detecting the scattering ray, and determines that an energy position gap is significant enough for energy calibration to be needed when detecting no scattering ray. In that case, a control section 20 interrupts measurement, and an alarming section 22 displays that energy calibration is needed. With that, an analyst can perform energy calibration at a precise timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray fluorescence analyzer, and more particularly to an energy dispersive X-ray fluorescence analyzer.

  An X-ray fluorescence analyzer includes a solid sample, a powder sample, or a liquid sample that is irradiated with primary X-rays and detects the fluorescent X-rays that are excited and emitted by the primary X-rays. Qualitative or quantitative analysis of the elements. X-ray fluorescence analyzers are roughly classified into two types: wavelength dispersion type and energy dispersion type. The former has a configuration in which fluorescent X-rays having a specific wavelength are selected by an X-ray spectrometer combining a spectral crystal and a slit and then detected by a detector. On the other hand, the latter has a configuration in which fluorescent X-rays are directly detected by a lithium drift type Si detector or the like without performing such wavelength selection, and thereafter, a detection signal is separated for each energy (that is, wavelength). . When creating a fluorescent X-ray spectrum, the wavelength dispersion type needs to perform wavelength scanning by a mechanical drive mechanism, whereas the energy dispersion type can obtain information on multiple wavelengths simultaneously without performing such wavelength scanning. Therefore, the fluorescent X-ray spectrum can be acquired in a short time.

  In the energy dispersive X-ray fluorescence analyzer, the energy position, that is, the horizontal axis position of the fluorescent X-ray spectrum shifts due to changes with time of the X-ray detector and the signal processing circuit at the subsequent stage. When the energy position deviation increases to a certain extent, for example, even if there is a spectral line of an element, the difference between the energy corresponding to the spectral line and the theoretical energy corresponding to the element increases. Is not identified as corresponding to the element. Alternatively, there is a possibility that erroneous identification is made when the spectral line corresponds to another element. Therefore, in order to correct the deviation of the energy position as described above, an energy calibration sample containing a known element is measured, and energy calibration is performed based on the measurement result (see Patent Document 1, etc.).

  Conventionally, the analyst himself has determined whether or not the energy calibration work as described above is necessary. Specifically, for example, the device usage time and the number of times of use are managed, and it is determined that energy calibration is necessary every predetermined usage time or every predetermined number of times, and an energy calibration sample is used. It is common to perform energy calibration. However, these methods have the following problems.

(1) In the above method, it is not always possible to appropriately know whether or not energy calibration is necessary. For this reason, energy calibration is often performed even though energy calibration is not yet required. In this case, instead of the sample to be measured, which is the measurement purpose, an energy calibration sample is set in the apparatus to perform the calibration work, and the measurement throughput for the sample to be measured is reduced.
(2) If the frequency of energy calibration work is reduced in order to avoid unnecessary energy calibration as described above, the energy position deviation may exceed the allowable range during the continuous measurement of one or more samples to be measured. is there. In that case, since it is unclear at which point the energy misalignment has exceeded the allowable range, all the measurement results already obtained are considered as unreliable or discarded, or each measurement result is one by one. It is necessary to evaluate whether or not the result is correct.

JP 10-48161 (paragraphs 0023-0027)

  The above problem is caused by the fact that it is impossible to accurately know that energy calibration is necessary when measuring a normal sample to be measured. The present invention has been made in view of these points, and the object of the present invention is to determine whether or not energy calibration is required when performing measurement on a normal sample to be measured without performing measurement using the sample for energy calibration. Is to provide a fluorescent X-ray analyzer capable of accurately grasping the above.

In order to solve the above-mentioned problems, the present invention irradiates a sample with primary X-rays generated by an X-ray source, and receives X-ray fluorescence emitted from the sample in response to the X-ray detector. In an energy dispersive X-ray fluorescence analyzer for analysis,
a) On the spectrum created based on the detection signal obtained by the X-ray detector, at least one of the spectral line by Rayleigh scattering and the spectral line by Compton scattering corresponding to the target element of the X-ray source is Scattered radiation detection means for detecting;
b) a determination unit that determines an energy position shift in the apparatus based on a detection result of at least one or both of a Rayleigh scattered spectrum line and a Compton scattered spectral line by the scattered ray detection unit;
c) information providing means for notifying the necessity of energy calibration based on the determination result by the determination means;
It is characterized by having.

  In the spectrum of X-rays emitted from the X-ray source, a very sharp characteristic X-ray peak having a wavelength unique to the metal element used for the target appears. When this sample is irradiated with X-rays, X-ray fluorescence is emitted from the sample and Rayleigh scattering and Compton scattering occur. Since the energy of the spectral lines (scattered lines) due to the scattering is theoretically determined, the spectral lines due to the Rayleigh scattering and the Compton scattering are set to predetermined values, even if the error is taken into consideration when the energy position shift does not occur in the apparatus. It should occur within the energy range. Conversely, when there are no spectral lines due to Rayleigh scattering and Compton scattering within the respective energy ranges, it can be estimated that there is a high possibility that an energy position shift has occurred.

  Therefore, in the fluorescent X-ray analysis apparatus according to the present invention, whether or not energy calibration is necessary by using at least one of Rayleigh scattered rays and Compton scattered rays obtained at the same time as fluorescent X-rays when measuring a sample to be measured. Judging. That is, when an X-ray spectrum is created based on a detection signal obtained by an X-ray detector for primary X-rays irradiated from the X-ray source to the sample to be measured, the scattered radiation detection means Either Rayleigh scattered radiation or Compton scattering corresponding to the target element of the radiation source is detected.

  At this time, the scattered radiation detection means can make one of the detection conditions of Rayleigh scattered radiation and Compton scattered radiation that the spectral radiation exists within a predetermined energy range corresponding to the target element of the X-ray source. In general, the characteristic X-rays inherent to the target element of the X-ray source are not one kind, and there are a plurality of Kα rays, Kβ rays, etc., and accordingly, a plurality of Rayleigh scattered rays also appear. Therefore, for example, the intensity ratio of a plurality of spectral lines such as the intensity ratio of Rayleigh scattered rays of Kα rays and Rayleigh scattered rays of Kβ rays may be added to one of the detection conditions of scattered rays.

  For example, when a detection result indicating that no spectral line exists within a predetermined energy range corresponding to the target element of the X-ray source and Rayleigh scattered radiation is not detected, the determination unit receives the detection result and receives the detection result in the apparatus. Judge that the energy position deviation exceeds the allowable range. The information providing means notifies that the energy calibration is necessary in response to the determination result. The notification method is not particularly limited, for example, by displaying a message or displaying a warning lamp, or by a sound such as a buzzer.

  As described above, scattering includes Rayleigh scattering and Compton scattering, and the intensity of the scattered radiation depends on the type of element contained in the sample. In particular, in the case of heavy elements, the intensity of Compton scattering decreases, and it may be difficult to find the spectral line. That is, depending on the type of element contained in the sample, it may be difficult to find the Compton scattered radiation, and judging the energy position shift using only the detection result of the Compton scattered radiation may cause an erroneous determination.

  Therefore, as a preferable aspect of the present invention, the determination unit determines that there is no energy positional deviation or is within an allowable range when a Rayleigh scattered spectrum line corresponding to the target element of the X-ray source is detected. can do.

  Although the intensity of Rayleigh scattered radiation also changes depending on the type of element contained in the sample, the intensity is usually not lowered to the extent that it cannot be detected. Therefore, by using Rayleigh scattered radiation, it is possible to reliably determine the energy position shift, and to improve the reliability of notification by the information providing means.

  In addition, under the condition where the kind of element contained in the sample is limited, the energy position shift can be accurately determined even using only Compton scattered rays. In addition, a combination of both, such as using Rayleigh scattered radiation when Compton scattered radiation is not found, is also conceivable.

  In addition, as one aspect of the X-ray fluorescence analyzer according to the present invention, a primary X-ray is irradiated on a sample to be measured, and a spectrum created based on a detection signal obtained by an X-ray detector according to the irradiation is used. Then, the energy position deviation is determined by the scattered radiation detection means and the determination means, and when the energy position deviation is within the allowable range, the measurement on the sample to be measured is continued, while the energy position deviation exceeds the allowable range. In the case where the information is provided, it is more preferable that the information providing unit further includes a measurement control unit for notifying the execution of energy calibration and interrupting the measurement of the sample to be measured.

  According to this configuration, it is possible to determine whether or not energy calibration is necessary as part of the measurement on the sample to be measured. If energy calibration is not necessary, the measurement on the sample to be continued is continued, and if energy calibration is necessary. It is possible to notify that the measurement is temporarily interrupted to prompt the execution of energy calibration. Accordingly, since the measurement is not continued in a situation where the energy position shift is large and the reliability of the measurement result is poor, it is possible to avoid performing a useless measurement. In addition, when there is no energy misalignment or within an allowable range, fluorescent X-ray spectral lines based on the already acquired spectrum can also be used for element identification and quantification, so there is no waste of measurement and efficiency. Measurement is possible.

  According to the fluorescent X-ray analyzer according to the present invention, the energy position shift is performed as a part of the normal measurement in a state in which any sample to be measured is set without setting the energy calibration sample in the apparatus and performing the actual measurement. It is possible to notify the analyst (user) by determining whether or not energy calibration is necessary. Therefore, the analyst can accurately know the timing of performing the energy calibration, and it is not necessary for the analyst to judge the timing of performing the calibration or to manage the usage time.

  In addition, it is possible to avoid unnecessary work such as setting the energy calibration sample and executing calibration work even though energy calibration is not required, so that the measurement throughput for the target sample to be measured is improved. .

  Furthermore, even when measuring multiple samples to be measured continuously, the necessity of energy calibration is accurately grasped by determining whether or not energy calibration is required for each measurement of the sample to be measured. It is possible to avoid performing unnecessary measurement in a situation where the energy position deviation is large. As a result, measurement results with poor reliability can be prevented from being mixed with measurement results with reliability, and the reliability of measurement results can be improved, and measurement efficiency can be improved by not performing unnecessary measurements. Can be planned.

  Hereinafter, an energy dispersive X-ray fluorescence analyzer which is an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a fluorescent X-ray analyzer according to the present embodiment.

  In FIG. 1, when primary X-rays emitted from an X-ray tube 1 strike a sample 2, fluorescent X-rays excited by the primary X-rays are emitted from the sample 2, and X-rays such as a lithium drift type silicon detector are used. The light enters the detector 3 and is detected as a current signal. The output current of the X-ray detector 3 is integrated by the preamplifier 4 and converted into a voltage signal, and is reset when the integrated voltage exceeds the threshold voltage. Thereby, the output signal of the preamplifier 4 becomes a stepped voltage pulse signal. The height of each step of this signal corresponds to the energy of each element contained in the sample 2. This voltage pulse signal is input to a proportional amplifier 5 including a waveform shaping circuit, and is formed into an appropriately shaped pulse having a wave height corresponding to the height of each step and output.

  An A / D converter (ADC) 6 samples and digitizes the analog signal in the form of a pulse wave at a predetermined sampling period, and a multi-channel analyzer (MCA) 7 selects each pulse signal according to the peak value of the digitized pulse signal. After the pulses are discriminated, they are counted, and a wave height distribution diagram, that is, an X-ray spectrum is created and input to the data processing unit 10. Data constituting the X-ray spectrum is stored in the spectrum storage unit 11. As shown in FIG. 2, in the X-ray spectrum, a spectrum line unique to each element appears as a peak at a position corresponding to the energy value of fluorescent X-rays emitted from the element contained in the sample to be analyzed. In the data processing unit 10, the peak detection unit 12 detects each peak appearing on the spectrum, and the qualitative / quantitative analysis unit 13 determines the content of the contained element based on the appearance position of the detected peak and its X-ray intensity value. Has the function of qualitative and quantitative.

  In the X-ray fluorescence analyzer of the present embodiment, the data processing unit 10 determines the energy misalignment that is the horizontal axis of the X-ray spectrum in addition to the basic functions as described above, and determines whether or not energy calibration is necessary. It has a characteristic function to notify. As a functional block for achieving this function, the data processing unit 10 includes a Rayleigh scattered ray detection unit 14 and an energy determination unit 15, and the notification unit 22 operates according to the determination result of the energy determination unit 15. A control unit 20 provided with an operation unit 21 controls the operation of each unit in the apparatus and performs a measurement operation. Note that at least a part of the data processing unit 10 and the control unit 20 can be realized by executing dedicated software installed in a general-purpose personal computer.

  Next, the operation centering on the judgment and notification of necessity of energy calibration, which is the characteristic function, will be described with reference to the flowchart of FIG.

  First, the analyst sets the sample 2 to be measured in the apparatus (step S1), and instructs the start of measurement from the operation unit 21 (step S2). A configuration is also conceivable in which the sample is automatically exchanged by a robot arm or the like, and when the exchange is completed, the start of measurement is automatically instructed automatically. In any case, when the measurement is started, the control unit 20 first performs a preliminary measurement as part of the measurement for the sample 2 to be measured (step S3). That is, under the control of the control unit 20, primary X-rays are irradiated from the X-ray tube 1 to the sample 2 to be measured for a short time (for example, about 10 to 20 seconds), and various X-rays emitted from the sample 2 accordingly. The X-ray detector 3 detects the line (step S4). Based on the detection signal obtained by the X-ray detector 3, the MCA 7 creates an X-ray spectrum and stores it in the spectrum storage unit 11 (step S5).

  In the data processing unit 10, the peak detection unit 12 detects a spectrum line (peak) appearing in the X-ray spectrum stored in the spectrum storage unit 11, and obtains energy of each spectrum line (step S6). In the X-ray spectrum, spectral lines due to fluorescent X-rays corresponding to various elements contained in the sample 2 to be measured appear, but in addition to this, characteristic X-rays derived from the target element of the X-ray tube 1 show the sample 2 to be measured. Rayleigh scattered rays and Compton scattered rays due to scattering at the moment also appear. The Rayleigh scattered ray detector 14 detects Rayleigh scattered rays from the X-ray spectrum using a predetermined energy range that is uniquely determined by the element of the target material of the X-ray tube 1 (step S7).

  Specifically, since Rayleigh scattered rays include Kα rays and Kβ rays having different energies, it is confirmed whether spectral lines exist in the energy ranges corresponding to the Kα rays and Kβ rays, respectively. If there is a spectral line, the X-ray intensity ratio is calculated. Then, when the intensity ratio is within a predetermined range, it is determined that the spectral line is derived from the target element of the X-ray tube 1. When there is no spectral line in the energy range corresponding to each of the Kα ray and Kβ ray, or when the X-ray intensity ratio deviates from the predetermined range even if it exists, it is derived from the target element of the X-ray tube 1 The result of detection that Rayleigh scattered rays cannot be detected is output.

  When the energy determination unit 15 receives the detection result from the Rayleigh scattered ray detection unit 14 and determines that there is a Rayleigh scattered ray (Y in step S8), there is no energy position shift (that is, energy position shift). Even if there is, it is determined that it is within the allowable range) (step S12). The determination result is sent to the control unit 20, and the control unit 20 continues the measurement as it is according to the determined sequence (step S13). For example, based on the qualitative / quantitative results obtained by the qualitative / quantitative analysis unit 13, it is determined whether or not more detailed measurement is necessary. 2 is irradiated with X-rays for a longer time.

  When the detection result that the Rayleigh scattered ray does not exist is obtained by the Rayleigh scattered ray detection unit 14 (N in step S8), the energy determination unit 15 exceeds the allowable range and the energy calibration is necessary. Is determined (step S9). The determination result is sent to the control unit 20, and the control unit 20 temporarily stops the measurement at that time (step S10). The determination result is sent to the notification unit 22, and the notification unit 22 displays a message indicating that energy calibration is necessary, and prompts the analyst to perform energy calibration (step S11). The analyst recognizes the necessity of energy calibration from this display. For example, the energy calibration sample is set in the apparatus instead of the sample 2 to be measured, and the energy calibration is instructed from the operation unit 21 to perform the energy calibration. Can be executed. Although the measurement is temporarily suspended in step S10, the analyzer may ignore the message and restart the measurement.

  As described above, according to the energy dispersive X-ray fluorescence spectrometer of the present embodiment, every time the sample 2 to be measured is newly set or exchanged and measurement is performed on the sample 2 to be measured, a part of the measurement is performed. (In preliminary measurement), the necessity of energy calibration is checked, and if energy calibration is necessary, a notification to that effect is given. Therefore, the analyst can know the exact timing for performing the energy calibration, and can also prevent an unnecessary measurement result having a large energy position shift without performing unnecessary energy calibration work.

  In addition to Rayleigh scattered rays, there are Compton scattered rays as well, and the theoretical energy position is also determined by the type of target element of the X-ray tube 1. In addition, it is not impossible to use Compton scattered radiation. However, the X-ray intensities of Rayleigh scattering and Compton scattering depend on the type of element contained in the sample 2 to be measured, while Rayleigh scattering is observed to some extent regardless of the type of element, while Compton. Scattering extremely decreases in intensity with respect to heavy elements, making it difficult to detect spectral lines. Therefore, when determining the energy position shift without limiting the type of element contained in the sample 2 to be measured, it is desirable to use Rayleigh scattered radiation. On the other hand, Compton scattered radiation can also be used, for example, by imposing conditions for limiting the sample to be measured to samples that do not contain heavy elements. It is also possible to determine the energy position shift by using both Rayleigh scattered rays and Compton scattered rays.

  Moreover, the said Example is an example, Comprising: Even if it changes suitably, a correction | amendment, and addition in the range of the meaning of this invention, it is clear that it is included by the claim of this application.

1 is a schematic configuration diagram of an energy dispersive X-ray fluorescence analyzer which is an embodiment of the present invention. The figure which shows an example of the X-ray spectrum acquired with the fluorescent X-ray-analysis apparatus of a present Example. The flowchart which shows the operation | movement centering on judgment and the alerting | reporting of the necessity of energy calibration in the fluorescent X-ray-analysis apparatus of a present Example.

Explanation of symbols

1 ... X-ray tube 2 ... Sample (sample to be measured)
3 ... X-ray detector 4 ... Preamplifier 5 ... Proportional amplifier 6 ... A / D converter 7 ... Multichannel analyzer (MCA)
DESCRIPTION OF SYMBOLS 10 ... Data processing part 11 ... Spectrum storage part 12 ... Peak detection part 13 ... Qualitative / quantitative analysis part 14 ... Rayleigh scattered ray detection part 15 ... Energy determination part 20 ... Control part 21 ... Operation part 22 ... Notification part

Claims (4)

In an energy dispersive X-ray fluorescence analyzer that irradiates a sample with primary X-rays generated by an X-ray source, and receives and analyzes the X-ray fluorescence emitted from the sample in response to an X-ray detector,
a) On the spectrum created based on the detection signal obtained by the X-ray detector, at least one of the spectral line by Rayleigh scattering and the spectral line by Compton scattering corresponding to the target element of the X-ray source is Scattered radiation detection means for detecting;
b) a determination unit that determines an energy position shift in the apparatus based on a detection result of at least one or both of a Rayleigh scattered spectrum line and a Compton scattered spectral line by the scattered ray detection unit;
c) information providing means for notifying the necessity of energy calibration based on the determination result by the determination means;
A fluorescent X-ray analysis apparatus comprising: The fluorescent X-ray analyzer according to claim 1,
The X-ray fluorescence analysis apparatus characterized in that the determination means determines that there is no energy positional deviation or is within an allowable range when a Rayleigh scattering spectral line corresponding to the target element of the X-ray source is detected. The X-ray fluorescence analyzer according to claim 1 or 2,
The scattered radiation detection means is characterized in that the presence of a spectral line within a predetermined energy range corresponding to the target element of the X-ray source is one of the detection conditions of Rayleigh scattered light and Compton scattered radiation. X-ray fluorescence analyzer. A fluorescent X-ray analyzer according to any one of claims 1 to 3,
The primary X-ray is irradiated to the sample to be measured, and the energy position is shifted by the scattered radiation detection means and the determination means using a spectrum created based on the detection signal obtained by the X-ray detector accordingly. If the energy position deviation is within the allowable range, the measurement of the sample to be measured is continued. If the energy position deviation exceeds the allowable range, the information providing means prompts the energy calibration to be performed. A fluorescent X-ray analyzer characterized by further comprising measurement control means for notifying and interrupting the measurement of the sample to be measured.

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