JPH0475458B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an X-ray microanalyzer, and more particularly, to improvement of analysis condition settings for a pulse height analyzer.

(Prior technology) An X-ray microanalyzer irradiates the surface of a sample with an extremely narrowly focused electron beam, and uses an X-ray spectrometer to measure the wavelength and intensity of the characteristic X-rays emitted from that part. It is an analytical instrument that qualitatively or quantitatively determines the contained elements, and is widely used in composition and materials research in various fields because it can analyze samples non-destructively.

One type of X-ray microanalyzer is
A linear crystal X-ray spectrometer configured to move a spectroscopic crystal that disperses X-rays according to wavelength along a straight line passing through an X-ray generation point on a sample according to a driving pulse, and detection of the spectrometer. Some devices are equipped with a pulse height analyzer (PHA) that analyzes the pulse height value of the signal.

Here, the pulse height analyzer compares the pulse height value of the supplied pulse with a base level V and a level V + ΔV which is larger than the base level V by a window width ΔV, and if the pulse height value has a value between these two levels, Only this pulse is counted, and the peak value of the pulse supplied from the amplifier is the base level V.
a first circuit that generates a pulse with a pulse width equal to the width of the period when the width is greater than the level V+ΔV; and a pulse with a pulse width equal to the width of the period when the peak value of the pulse supplied from the amplifier is larger than the level V+ΔV and an anti-coincidence circuit that counts the output pulses of the first circuit only when pulses are sent from the first circuit and no pulses are sent from the second circuit. The reason for using this pulse height analyzer is as follows. That is, based on the difference in energy, the wave height of the detection pulse of the secondary or higher-order line is clearly different from the wave height of the detection pulse of the primary line, so the above function of the pulse height analyzer is used to detect the primary line. This is because the accuracy of spectrum analysis can be improved by counting pulses and not counting detected pulses of secondary or higher order.

By the way, the base level and window width, which are the analysis conditions for such a wave height analyzer, are determined depending on the spectroscopic crystal and the spectroscopic angle, that is, the energy of the characteristic X-ray, and usually the standard sample of the element to be analyzed is is determined for each characteristic X-ray.

For example, in an apparatus configured to be controlled by a computer, the base level and window width are checked in advance for each characteristic X-ray and the base level and window width are individually stored.
The base level and window width can be set by the computer when analyzing the relevant element.

In addition, the base level and window width of the characteristic X-ray of the element to be analyzed are calculated from an approximation formula obtained in advance using the characteristic X-rays of one or two reference elements, and the values are set by a computer. You can also do that.

(Problem to be solved by the invention) However, in such a computer-controlled device, it takes a large amount of man-hours to determine the base level and window width using a standard sample for each characteristic X-ray. . Furthermore, in order to calculate and set the base level and window width of the pulse height analyzer each time the spectroscopic crystal is moved, a large amount of man-hours are required to create a program, resulting in an increase in program capacity.

The present invention has been made in view of the above points, and an object of the present invention is to automatically set the base level and window width of a pulse height analyzer at any spectral position without depending on the calculation results of a program. The object of the present invention is to realize an X-ray microanalyzer that does not require a large number of man-hours to determine the width or increase the program capacity.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, is a crystal rectilinear movement system in which a spectroscopic crystal is configured to move along a straight line passing through an X-ray generation point on a sample in response to a driving pulse. Type X
In an X-ray microanalyzer equipped with a line spectrometer and a pulse height analyzer that analyzes the peak value of a detection signal of the spectrometer, a signal for generating a signal representing the distance between the spectroscopic crystal and the X-ray generation point. a generating circuit, a first arithmetic unit for converting the output signal of the signal generating circuit into a signal corresponding to the reciprocal of the signal value, and the output signal of the signal generating circuit corresponding to the reciprocal of the square root of the signal value. a base level setter for setting a base level of the pulse height analyzer based on the output signals of the first and second computing units;
The present invention is characterized by further comprising a window width setting device for setting the window width of the pulse height analyzer based on the output signal of the arithmetic unit.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 1 is an X-ray source (sample) that emits X-rays 3 when irradiated with an electron beam 2; 4 is a spectroscopic crystal that disperses the X-rays 3 emitted from the X-ray source 1; is the slit of the X-ray detector XD that detects the X-rays 6 dispersed and reflected by the spectroscopic crystal 4, and these X-ray source 1, spectroscopic crystal 4, and slit 5 are located on the circumference 7 called the Rowland circle. It consists of an X-ray spectrometer. In this X-ray spectrometer, the spectroscopic crystal 4 is configured to move on a straight line 8 passing through the X-ray source 1 in response to a drive pulse output from a drive pulse source 9. Therefore, the center 10 of the Rowland circle 7 and the slit 5 also move, and such an X-ray spectrometer is called a crystal rectilinear type. 11 is a pulse motor that converts the drive pulse output from the drive pulse source 9 into a rotation amount in order to move the spectroscopic crystal 4; 12 is a potentiometer 1 that controls the rotation of the pulse motor 11;
This is a gear for converting into 3 rotations. As a result, the amount of movement of the spectroscopic crystal 4 is controlled by the potentiometer 13.
This will be converted into a change in resistance value. 14 is a resistance voltage converter that converts a change in the resistance value of the potentiometer 13 into a voltage change; 15 is a first unit that calculates the reciprocal of the voltage converted by the resistance voltage converter 14;
A computing unit 16 is a second computing unit that computes the reciprocal of the square root of the voltage converted by the resistance voltage converter 14. The output signals of each of these arithmetic units 15 and 16 are as follows:
The signals are applied to an automatic/manual switch 19 via calibrators 17 and 18 that adjust the input/output ratio, respectively. Setting signals corresponding to the computing units 15 and 16 are applied to the automatic manual switching device 19 from manual setting devices 20 and 21, respectively. And the automatic manual switching device 1
9 to these computing units 15 and 16 depending on the switching state.
The output signal or the setting signal of the manual setting devices 20 and 21 is selectively outputted to the base level setting device 23 and the window width setting device 24 of the pulse height analyzer 22. As a result, only those detection signals from the X-ray detector XD applied via the amplifier 25 that are within a predetermined base level and window width are selected by the pulse height analyzer 22.

The operation of the device configured in this way will be explained.

Assuming that a characteristic X-ray with wavelength λÅ is detected at a distance of lmm from point 0 to point C in Figure 1, then l=(2R/2d)nλ...(1) R; radius d of Rowland circle 7; spectroscopy The following relationship holds true: interplanar spacing n of the crystal 4; an integer (1, 2,...). The energy of the characteristic X-ray
Assuming EkeV, λE=12.4...(2), so from equations (1) and (2), l=n・12.4(2R/2d)(1/E)...(3) is obtained. .

On the other hand, the height of the primary pulse of the detection signal output from the X-ray detector XD is proportional to the energy of the incident X-ray. Then, if k is the proportional coefficient between the height (H) and energy (E) of the pulse applied to the pulse height analyzer 22 via the amplifier 25, then the following relationship holds: H=k・E...(4) Therefore, the pulse height value of the pulse applied to the pulse height analyzer 22 is H=k・n・12.4 (2R/2d) (1/l) (5). Also, since the appropriate window width W of the pulse height analyzer 22 is W∝√ considering the statistical fluctuation of ion pairs created in the X-ray detector XD, W=h・√1...( 6) h: Can be expressed as proportionality coefficient.

Note that the proportionality coefficient k in equation (5) and the proportionality coefficient h in equation (6) change depending on the gain of the amplifier 25 and the interplanar spacing d of the spectroscopic crystal used.

FIG. 2 is an explanatory diagram showing the correspondence between the pulse height value H and the distance l. As is clear from Fig. 2, by appropriately setting the proportionality coefficients k and h, when the distance l changes from L ₁ to L ₂ (L ₁ < L ₂ ), the curve can be adjusted to any appropriate height. It can be shifted.

That is, if the number of driving pulses required to move the spectroscopic crystal 4 from L ₁ to L ₂ is p, then the change Δl in the distance l when the spectroscopic crystal 4 is driven by n pulses is as follows: Δl = (n/ p) (L ₂ − L ₁ ) ...(7). Here, the characteristic _X
The pulse height value of the line is Ho, and the window width with this pulse height Ho as the center level is Wo (the base level is the lower limit level of the window width, so the base level at this time is equal to the pulse height Ho). ), by setting the aforementioned proportionality coefficients k and h, l ₀ to Δl
The pulse height value H of characteristic X-rays spectrally separated at l positions is given by H=H ₀ +ΔH=const・1/(l ₀ +Δl)...(8) Similarly, the window width W is given by W= W ₀ +ΔW=const・1/(√ ₀ +) ...(9) It is given by.

Therefore, as shown in FIG.
2 to the potentiometer 13, the resistance value can be changed according to the value of l,
By converting the resistance value into a voltage using the resistance voltage converter 14, a voltage proportional to the value of l can be obtained. Therefore, the pulse motor 11, gear 12, potentiometer 13 and resistance voltage converter 14 are as follows:
This constitutes a signal generation circuit for generating a signal representing the distance between the spectroscopic crystal 4 and the X-ray generation point. Then, the output signal of this signal generation circuit,
That is, the output voltage of the resistance voltage converter 14 is
5, a voltage proportional to the peak value H of the pulse that satisfies equation (5) can be obtained, and the calculation unit 1
6, a voltage related to the window width W that satisfies equation (6) can be obtained. Note that the proportionality coefficients k and h are changed by the calibrators 17 and 18 in order to determine an appropriate pulse height value H ₀ and window width W ₀ for l ₀ .

The automatic manual switch 19 has the above-mentioned computing units 15 and 16.
output signals are given via the calibrators 17 and 18, and when the switching state of the automatic/manual switch 19 is automatic, these signals are output to the window width setter 24 and base level setter 23 of the pulse height analyzer 22. be done. As a result, the base level setter 23 and the window width setter 24 respectively output the window width W corresponding to l and the base level (since the base level is the lower limit level of the window width W, W/ 2 (calculated by the base level setter 23 which receives the output signals of both the arithmetic units 15 and 16) are given to the pulse height analyzer 22, and added via the amplifier 25. The pulse height analyzer 22 selects only those detection signals of the X-ray detector XD that are within a predetermined base level and window width. As is clear from these, the wave height analyzer 2 corresponding to any l value
The base level setting value and window width setting value of No. 2 are automatically set in conjunction with the movement of the spectroscopic crystal 4.

This configuration eliminates the need for a large number of man-hours, such as determining the base level and window width using a standard sample for each characteristic X-ray, and also makes it possible to set the base level and window width. It is no longer necessary to store instructions for the analysis in memory, reducing the capacity of the analysis program and greatly reducing the number of steps required to create the program.

(Effects of the Invention) As explained above, according to the present invention, the base level and window width of the pulse height analyzer at any spectral position can be automatically set without depending on the calculation results of the program, and the base level and window width can be set automatically. It is possible to realize an X-ray microanalyzer that does not require a large number of man-hours or increase the program capacity in order to obtain the .

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the correspondence between pulse peak value H and distance l. 1... X-ray source (sample), 4... Spectroscopic crystal, 5...
...slit, 9...pulse source, 11...pulse motor, 12...gear, 13...potentiometer, 14...resistance voltage converter, 15, 16...computer, 17, 18...calibrator , 19... Automatic manual circuit, 20, 21... Manual setting device, 22... Wave height analyzer, 23... Base level setting device, 24...
Window width setter, 25...Amplifier, XD...
X-ray detector.

Claims (1)

[Claims] 1. A linear crystal X-ray spectrometer configured such that a spectroscopic crystal moves on a straight line passing through an X-ray generation point on a sample in response to a driving pulse, and a detection signal of the spectrometer. An X-ray microanalyzer equipped with a pulse height analyzer for analyzing wave height values, comprising: a signal generation circuit for generating a signal representing the distance between the spectroscopic crystal and the X-ray generation point; and an output signal of the signal generation circuit. a first arithmetic unit for converting the output signal of the signal generation circuit into a signal corresponding to the reciprocal of the signal value; and a second arithmetic unit for converting the output signal of the signal generation circuit into a signal corresponding to the reciprocal of the square root of the signal value.
a base level setter for setting the base level of the pulse height analyzer based on the output signals of the first and second calculators; and a base level setting device for setting the base level of the pulse height analyzer based on the output signals of the second calculator. An X-ray microanalyzer comprising: a window width setting device for setting a window width of the wave height analyzer;