JP2010286288A - Control method for x-ray spectrometer, and x-ray spectrometer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for X-ray spectrometer of flat spectral crystal type, where the interval of data points of X-ray intensity distribution is constant with respect to wavelength, and to provide the X-ray spectrometer of flat spectral crystal type that uses the control method. <P>SOLUTION: The X-ray spectrometer of flat spectral crystal type has a conventional constitution constituted of a multi-capillary X-ray lens 7, a flat-type spectral crystal 8 and an X-ray detector 6, in relation to which the X-ray spectrometer a drive control section 26 for controlling a drive section (not shown) of the flat-type spectral crystal 8 and the X-ray detector 6 is installed. The drive control section 26 changes the rotational speed of the flat-type spectral crystal 8 and the X-ray detector 6 momentarily so that the wavelength interval of the X-ray intensity output from a counting section 23 can be made constant, within a fixed counting period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray spectrometer and an X-ray spectroscopy method used in an X-ray analyzer such as an X-ray fluorescence analyzer, an electron probe microanalyzer (EPMA), and a scanning electron microscope (SEM). The present invention relates to a control method of an X-ray spectrometer used in a wavelength dispersion type (WDS) X-ray analyzer and an X-ray spectrometer using the control method.

  In an electron beam probe microanalyzer (EPMA), when a sample is irradiated with an electron beam having a medium diameter of about 20 to 30 keV as an excitation beam, the inner electrons of the sample contained therein are excited. By analyzing the characteristic X-rays emitted to the outside (characteristic X-rays), the elements are identified and quantified, and the distribution of the elements is examined. In addition, the scanning electron microscope (SEM) generally detects secondary electrons and reflected electrons generated from the irradiation position of the electron beam, but recently, an X-ray analysis is performed by adding an energy dispersive X-ray detector. A device that enables this is also being developed.

  Conventionally, this type of X-ray analyzer has a wide configuration as shown in FIG. 5 as an X-ray spectrometer for efficiently separating intrinsic X-rays emitted from a minute region that can be regarded as one point on the sample surface. (See, for example, Patent Document 1). In this X-ray spectrometer, a minute region 2 irradiated with an electron beam on a sample 1, a Johansson-type curved spectroscopic crystal 4 and an X-ray detector 6 are placed on a Roland circle 3 on the same reference plane (the drawing sheet). The curved spectral crystal 4 and the X-ray detector 6 are moved along the Roland circle 3 by a moving means (not shown) such as a link mechanism with the minute region 2 on the sample 1 as a fixed point. Since the spectral wavelength is determined by the positions of the curved spectral crystal 4 and the X-ray detector 6, the type of element is specified by performing wavelength scanning by movement thereof.

  In addition, as shown in FIG. 6, the X-rays emitted from the sample 1 are converged by a multicapillary X-ray lens (sometimes called a polycapillary) 7 and collimated to be introduced into a flat plate crystal crystal 8 for flat plate spectroscopy. A configuration of an X-ray spectrometer that detects X-rays separated by the crystal 8 by sending it to the X-ray detector 6 is also known (see Patent Document 2). Also in this case, similarly to the example of FIG. 7, wavelength scanning is performed by changing θ while maintaining the double angle relationship (θ, 2θ) between the flat plate crystal 8 and the X-ray detector 6. Can do.

JP 2001-33408 A JP 2005-233670 A

  Incidentally, as described above, the curved spectral crystal type X-ray spectrometer shown in FIG. 5 has the curved spectral crystal 4 and the X-ray detector while maintaining a predetermined angular relationship on the Roland circle 3 in order to perform wavelength scanning. 6 needs to be moved. However, when the spectroscopic crystal 4 is moved, the relative position and direction of the spectroscopic crystal 4 and the sample 1 change, so that the extraction angle of X-rays radiated from the sample changes, which hinders analysis accuracy and data analysis. End up. In order to prevent this, an X-ray spectrometer having a structure shown in FIG. 7 is actually used. This X-ray spectrometer is configured such that the spectral crystal 4 moves on a straight line 9 passing through the minute region 2 so that the X-ray extraction angle is kept constant. Therefore, as the spectral crystal 4 moves, the center position of the Roland circle 3 moves, and the X-ray detector 6 also moves so as to maintain a predetermined angular relationship with the spectral crystal on the Roland circle where the center position has moved. In this X-ray spectrometer, since the distance from the sample 1 to the spectroscopic crystal 4 is proportional to the wavelength, the number of rotations of the motor that moves the spectroscopic crystal and the wavelength are also proportional. Thereby, the interval between the data points of the X-ray intensity distribution obtained by scanning the spectroscopic crystal and the X-ray detector is constant with respect to the wavelength.

  On the other hand, the X-ray spectrometer of the flat plate crystal type shown in FIG. 6 rotates the flat plate crystal 8 about an axis 8a perpendicular to the paper surface, and the X-ray detector 6 is also set about the axis 8a. The circumference of the spectroscopic crystal 8 is moved so as to maintain an angle 2θ that is twice the rotation angle θ. In this X-ray spectrometer, since the X-ray extraction angle is always kept constant, it is not necessary to move the spectroscopic crystal as in the X-ray spectrometer of FIG. 5 or FIG. In addition, unlike a curved spectroscopic X-ray spectrometer, it is not necessary to place a sample, a spectroscopic crystal and an X-ray detector on the Roland circle. The degree of freedom in design is higher than when it is used. Therefore, the curved spectral crystal type X-ray spectrometer is advantageous in that it is relatively applicable even when it is difficult to design the X-ray analyzer due to restrictions on the sample and installation space.

  However, when wavelength scanning is performed with the X-ray spectrometer having the configuration shown in FIG. This is because the rotational speed of the motor that moves the spectroscopic crystal and the X-ray detector is proportional to the angle θ. From the Bragg condition, the X-ray intensity distribution has a wide wavelength interval on the short wavelength side and a narrow wavelength interval on the long wavelength side. End up.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a flat plate crystal type X-ray spectrometer in which the interval between data points of the X-ray intensity distribution is constant with respect to the wavelength. And a flat plate crystal X-ray spectrometer using the control method.

  The X-ray spectrometer control method according to the first aspect of the present invention for solving the above-described problem is that X-rays emitted from a minute region on a sample are converted into parallel light in accordance with excitation rays irradiated on the sample. A multi-capillary X-ray lens, a flat plate crystal disposed on the optical path of parallel X-rays emitted from the multi-capillary X-ray lens, and an X-ray detector for detecting X-rays dispersed by the flat plate crystal Driving means for rotating the flat plate crystal and the X-ray detector while maintaining a predetermined angular relationship around the intersection of the surface of the flat plate crystal and the parallel X-ray, and the X-ray detector An X-ray spectroscope control method comprising: X-ray intensity acquisition means for acquiring X-ray intensity by selecting the detection signals of (2) and counting the selected detection signals at regular time intervals, Keep X-ray intensity acquisition wavelength interval constant And controlling said drive means so.

  The X-ray spectrometer control method according to the second invention includes a multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample in accordance with excitation rays irradiated on the sample, A plate spectral crystal disposed on the optical path of parallel X-rays emitted from the multicapillary X-ray lens, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal, and the Driving means for driving the X-ray detector to rotate at a constant rotational speed while maintaining a predetermined angular relationship around the intersection of the surface of the flat plate spectral crystal and the parallel X-ray; and a detection signal from the X-ray detector And an X-ray intensity acquisition means for acquiring the X-ray intensity by counting the selected detection signals, and a method for controlling the X-ray intensity acquisition wavelength interval. The counting time interval is set to be constant. Causes ized, based on the X-ray intensity obtained by the X-ray intensity acquisition means the count time, and calculates the X-ray intensity per unit time.

  According to a third aspect of the present invention, there is provided an X-ray spectrometer comprising: a multicapillary X-ray lens that collimates X-rays emitted from a minute region on a sample in accordance with excitation rays irradiated on the sample; and the multicapillary A plate spectral crystal disposed on the optical path of parallel X-rays emitted from the X-ray lens, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal, and the X-ray detection And a drive means for rotationally driving the detector while maintaining a predetermined angular relationship around the intersection of the surface of the plate spectral crystal and the parallel X-ray, and a detection signal from the X-ray detector. An X-ray spectrometer having an X-ray intensity acquisition means for acquiring an X-ray intensity by counting a detection signal at a constant time interval, wherein the driving is performed so that the acquisition wavelength interval of the X-ray intensity is constant. Drive control means for controlling the means I am characterized in.

  An X-ray spectrometer according to a fourth aspect of the invention includes a multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample according to excitation rays irradiated on the sample, and the multicapillary. A plate spectral crystal disposed on the optical path of parallel X-rays emitted from the X-ray lens, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal, and the X-ray detection And selecting a detection signal from the X-ray detector, and a driving means for rotating the detector at a constant rotational speed while maintaining a predetermined angular relationship about the intersection of the surface of the flat plate crystal and the parallel X-ray. An X-ray spectrometer having an X-ray intensity acquisition means for acquiring an X-ray intensity by counting the selected detection signals, wherein the counting is performed so that an acquisition wavelength interval of the X-ray intensity is constant. Counting time system that changes the time interval of And means, based on the X-ray intensity with the counting time to be acquired by the X-ray intensity acquisition means, characterized in that it comprises a processing means for calculating the X-ray intensity per unit time, the.

  According to the control method of the X-ray spectrometer and the X-ray spectrometer using the control method according to the present invention, the change rate of the angle direction of the flat plate crystal and the X-ray detector or the counting time of the X-ray intensity is momentarily measured. By controlling the above, the acquisition wavelength interval of the X-ray intensity can be made constant. The present invention only controls the rotation driving means for rotating the spectral crystal and the X-ray detector or the data processing of the detection signal from the X-ray detector with respect to the conventional flat plate spectral crystal type X-ray spectrometer. Therefore, it can be easily realized by using the configuration of an existing apparatus.

1 is a schematic configuration diagram of an X-ray optical system of an X-ray spectrometer that is a first embodiment of the present invention. The graph (a) showing an example of X-ray intensity distribution acquired with the conventional flat plate crystal-crystal type | mold X-ray spectrometer, and the enlarged view (b) of the one part. The graph (a) showing an example of X-ray intensity distribution acquired with the X-ray spectrometer which is 1st Example of this invention, and the enlarged view (b) of the part. The schematic block diagram of the X-ray optical system of the X-ray spectrometer which is 2nd Example of this invention. FIG. 6 is a schematic configuration diagram of an X-ray optical system of a conventional curved spectral crystal X-ray spectrometer. The schematic block diagram of the X-ray optical system of the conventional flat plate crystal type X-ray spectrometer. FIG. 6 is a schematic configuration diagram of an X-ray optical system of a conventional curved spectral crystal X-ray spectrometer.

  A first embodiment of an X-ray spectrometer according to the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an X-ray spectrometer according to the present embodiment. The same components as those already described in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The X-ray spectrometer according to this embodiment has a multi-capillary X-ray lens 7 that focuses and collimates the X-rays emitted from the minute region 2 of the sample 1 in the same manner as the conventional configuration described in FIG. A flat plate crystal 8 for splitting X-rays collimated by the multicapillary X-ray lens 7 and an X-ray detector 6 for detecting the X-ray intensity of the X-rays split by the flat plate crystal 8 are provided. The plate spectral crystal 8 and the X-ray detector 6 are rotationally driven by a drive unit (not shown) including a link mechanism and the like while maintaining a double angle relationship (θ, 2θ) about an axis 8a perpendicular to the paper surface. Thereby, wavelength scanning of the X-rays emitted from the minute region 2 is performed.

  For example, a scintillation counter is used as the X-ray detector 6. When an X-ray photon is incident, the X-ray detector 6 generates a pulse signal having a wave height corresponding to the energy of the X-ray photon. This pulse signal is input to the signal processing unit 9, amplified by a preamplifier, and then only a pulse signal having a peak value that falls within a predetermined discrimination range set in advance by a pulse height selector is selected. The selected pulse signal is counted by the counting unit 23, and a count value corresponding to the number of pulse signals obtained in a certain counting time is given to the data processing unit 24 as an X-ray intensity. The data processing unit 24 creates an X-ray intensity distribution from the input data, and executes qualitative analysis, quantitative analysis, or state analysis based on the intensity distribution. The generated X-ray intensity distribution and analysis result are displayed on the display unit 25.

  In the X-ray spectrometer of the present embodiment, the counting time of the counting unit 23 is constant, and the X-ray intensity acquisition wavelength interval is constant by changing the rotational speed of the flat plate crystal 8 and the X-ray detector 6 every moment. In addition to the configuration of the conventional X-ray spectrometer, a drive control unit 26 for controlling the drive unit is provided. An input unit 21 is attached to the drive control unit 26, and when an analyst (operator) inputs and sets the acquisition wavelength interval Δλ of the X-ray intensity to the input unit 21, the drive control unit 26 outputs the X output from the counting unit 23. The drive unit is controlled so that the wavelength interval of the line intensity is constant at Δλ.

  Next, using FIG. 2 and FIG. 3, the X-ray intensity distribution obtained with the spectrometer of the present embodiment is compared with the X-ray intensity distribution obtained with a conventional spectrometer. 2A shows an example of an X-ray intensity distribution obtained from a conventional spectroscope, and FIG. 3A shows an X-ray obtained by the spectroscope of this embodiment for the same example as FIG. 2A. The intensity distribution is shown. 2 (b) and 3 (b) are enlarged views of parts of FIG. 2 (a) and FIG. 3 (a), respectively.

2A and 3A, it seems that the same X-ray intensity distribution is obtained. However, these distributions are actually a collection of data points, and it can be seen that when a part of the distribution is enlarged, the data points are plotted while being spaced apart from each other (FIGS. 2B and 3B). Furthermore, in the X-ray intensity distribution of the conventional spectrometer, the horizontal axis (wavelength) interval is not constant, and the wavelength interval Δλi on the short wavelength side is larger than the wavelength interval Δλj on the long wavelength side. It can be seen from b). This is because Bragg's condition λ = 2 d sinθ (λ: wavelength, d: lattice constant)
Can be used to explain. That is, since the conventional X-ray spectrometer acquires the X-ray intensity at a constant rotation speed and a constant counting time, θ changes at regular intervals with respect to time. However, since the spectral wavelength λ changes with sin θ, if the change in θ is constant, the change in λ does not become constant.
On the other hand, in this embodiment, the interval of θ is controlled so that λ changes at equal intervals. Specifically, the sin θ is controlled to be constant by changing the rotational speeds of the plate spectral crystal 8 and the X-ray detector 6 every moment while keeping the counting time constant. Thereby, as shown in FIG. 3B, a graph in which the wavelength interval is constant can be obtained.

  A second embodiment of the X-ray spectrometer according to the present invention will be described with reference to FIG. The X-ray spectrometer according to this embodiment is such that the rotation speed of the plate crystal crystal 8 and the X-ray detector 6 is constant, and the acquisition wavelength interval of the X-ray intensity is constant by controlling the counting time every moment. In addition to the configuration of the conventional flat plate crystal type X-ray spectrometer, a counting time control unit 27 and a second counting unit 29 that measures the counting time determined by the counting time control unit 27 are provided. Yes. The first counting unit 28 counts the detection signals selected by the signal processing unit 22 in the same manner as the counting unit 23 of the first embodiment, and the counting time is measured by the second counting unit. The input unit 21 is attached to the counting time control unit 27, and when the analyst inputs and sets the acquisition wavelength interval Δλ of the X-ray intensity to the input unit 21, the counting time control unit 27 outputs the X output from the first counting unit 28. The counting time of the second counting unit 29 is controlled so that the wavelength interval of the line intensity becomes constant at Δλ.

  The counting time control unit 27 of this embodiment makes the wavelength interval of the X-ray intensity constant by changing the counting time of the first counting unit 28 every moment, but the problem is that the counting time of the X-ray intensity varies depending on the wavelength. Occurs. In order to prevent this, the data processing unit 24 calculates the X-ray intensity per unit time by dividing the X-ray intensity obtained by the first counting unit 28 by the counting time of the second counting unit. Thereby, it is possible to obtain an accurate X-ray intensity that is not affected by the change in the counting time.

DESCRIPTION OF SYMBOLS 1 ... Sample 2 ... Micro area | region 3 ... Roland circle 4 ... Curved spectral crystal 5 ... Detector slit 6 ... X-ray detector 7 ... Multicapillary X-ray lens 8 ... Flat plate spectral crystal 8a ... Axis 9 ... Straight line 21 ... Input part 22 ... Signal processing unit 23 ... Counting unit 24 ... Data processing unit 25 ... Display unit 26 ... Drive control unit 27 ... Counting time control unit 28 ... First counting unit 29 ... Second counting unit

Claims (4)

  A multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample according to excitation rays irradiated on the sample, and an optical path of parallel X-rays emitted from the multicapillary X-ray lens A plate spectral crystal, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal and the X-ray detector, the surface of the plate spectral crystal and the parallel X A driving means for rotating and maintaining a predetermined angular relationship around the intersection of the lines and a detection signal from the X-ray detector are selected, and the selected detection signals are counted at a constant time interval. An X-ray spectrometer control method comprising: X-ray intensity acquisition means for acquiring line intensity, wherein the driving means is controlled so as to make the acquisition wavelength interval of the X-ray intensity constant. Control method of the line spectrometer.   A multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample according to excitation rays irradiated on the sample, and an optical path of parallel X-rays emitted from the multicapillary X-ray lens A plate spectral crystal, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal and the X-ray detector, the surface of the plate spectral crystal and the parallel X A driving means for rotating and driving at a constant rotational speed while maintaining a predetermined angular relationship around the intersection of the lines, a detection signal from the X-ray detector is selected, and the selected detection signal is counted to calculate X And an X-ray spectroscope control method having X-ray intensity acquisition means for acquiring a line intensity, wherein the counting time interval is changed so as to make the acquisition wavelength interval of the X-ray intensity constant, and Obtained by means of obtaining line strength Is based on the X-ray intensity with the counting time, a control method of the X-ray spectrometer and calculates the X-ray intensity per unit time.   A multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample according to excitation rays irradiated on the sample, and an optical path of parallel X-rays emitted from the multicapillary X-ray lens A plate spectral crystal, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal and the X-ray detector, the surface of the plate spectral crystal and the parallel X A driving means for rotating and maintaining a predetermined angular relationship around the intersection of the lines and a detection signal from the X-ray detector are selected, and the selected detection signals are counted at a constant time interval. An X-ray spectrometer having an X-ray intensity acquisition means for acquiring a line intensity, comprising: a drive control means for controlling the drive means so as to make the acquisition wavelength interval of the X-ray intensity constant. X-ray spectrometer.     A multicapillary X-ray lens that collimates X-rays emitted from a minute region on the sample according to excitation rays irradiated on the sample, and an optical path of parallel X-rays emitted from the multicapillary X-ray lens A plate spectral crystal, an X-ray detector for detecting X-rays dispersed by the plate spectral crystal, the plate spectral crystal and the X-ray detector, the surface of the plate spectral crystal and the parallel X A driving means for rotating and driving at a constant rotational speed while maintaining a predetermined angular relationship around the intersection of the lines, a detection signal from the X-ray detector is selected, and the selected detection signal is counted to calculate X An X-ray spectrometer having an X-ray intensity acquisition means for acquiring a line intensity, the counting time control means for changing the time interval of the counting so as to make the acquisition wavelength interval of the X-ray intensity constant, and Taken with X-ray intensity acquisition means X-ray spectrometer, characterized in that it comprises, the arithmetic processing means for calculating the X-ray intensity per unit time, the basis of the X-ray intensity with the counting time being.

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