JP5251330B2 - X-ray analyzer - Google Patents

Description

  The present invention relates to an X-ray analyzer that irradiates a sample with excitation rays such as primary X-rays and thereby detects X-rays emitted from the sample.

  In general, an X-ray fluorescence analyzer irradiates a solid, powder or liquid sample with primary X-rays as excitation rays, and emits X-rays emitted from the sample when excited by the primary X-rays. By detecting, qualitative and quantitative analysis of elements contained in the sample is performed. In such a fluorescent X-ray analyzer, in order to adjust the size of the primary X-ray irradiation area on the sample, an irradiation area limiting unit (aperture) is arranged between the X-ray source and the sample. (See Patent Document 1 and the like).

  In addition, it is also known in the past to provide a diaphragm having a variable diameter so that a minute region on a sample can be analyzed. The change in the diameter of the aperture is performed by mechanically moving a shielding plate having a plurality of aperture holes having different sizes, and a pulse motor (stepping motor) is used for the movement. . In such a mechanism, when the aperture diameter is changed, a pulse signal corresponding to the change is given to the pulse motor to move the shielding plate so that the desired aperture hole is positioned on the optical axis of the primary X-ray. (In this specification, this state is referred to as “setting the aperture”). However, an unintentional diaphragm is set when a step-out such as slip occurs during the movement of the shielding plate, or a disturbance such as strong mechanical vibration is applied even when the shielding plate is stopped. It can even happen that the primary X-rays are blocked by and the sample does not receive the primary X-rays.

  X-ray fluorescence analyzers are often used for analysis of harmful substances and impurities whose use is regulated. However, as described above, the state where primary X-rays do not hit the sample or the X-ray irradiation area is more than intended. When analysis is performed in a narrow state, there is a problem that an erroneous result that the content of harmful substances or impurities to be detected is zero or lower than a reference value may be obtained. In order to solve this and ensure the reliability of the analysis, it is necessary to ensure that the aperture for limiting the X-ray irradiation area is set appropriately.

JP 2003-207466 A

  Of course, for example, if a sensor capable of detecting that the target aperture of the plurality of apertures is located on the optical axis of the primary X-ray is added, the above problem can be solved. However, such measures require the addition of hardware such as circuits and sensors, and an increase in cost is inevitable, and it may be difficult to add such hardware due to space or other reasons.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to limit the X-ray irradiation area by means of control and processing using a CPU without adding hardware. An object of the present invention is to provide an X-ray analyzer capable of reliably detecting an abnormal setting such as an aperture and improving the reliability of collected data.

In order to solve the above problems, the present invention is an X-ray analyzer that irradiates a sample with excitation rays emitted from an excitation source and introduces X-rays emitted from the sample into a detector. Either an area limiter for limiting the irradiation area of the excitation beam disposed between the excitation source and the sample, or an area limiter for limiting the field of view disposed between the sample and the detector. In an X-ray analyzer comprising
a) a shielding plate provided with a plurality of apertures of different sizes as the region limiting portion;
b) a drive mechanism including a pulse motor for moving the shielding plate to selectively move the aperture hole on the optical axis of the excitation line or X-ray;
c) position detecting means for detecting that the shielding plate has reached the first position;
d) Along with the change of the aperture hole, after applying the number of pulses corresponding to the aperture hole before the change to the pulse motor to return the shielding plate to the second position, a detection signal by the position detection means is further generated. Movement control means for moving the shielding plate by applying pulses to the pulse motor until obtained;
e) In the movement control by the movement control means, the number of pulses until the shielding plate comes from the second position to the first position is counted, and the count value is used to immediately before the change of the aperture hole. An abnormality detecting means for detecting that the position of the shielding plate is abnormal;
With
The movement control means provides the pulse motor with the number of pulses corresponding to the aperture for each predetermined number of analysis executions even when the aperture is not changed, so that the shielding plate is moved to the second position. After returning, further moving the shielding plate by giving a pulse to the pulse motor until a detection signal by the position detection means is obtained,
In the movement control, the abnormality detection means uses a count value of pulses until the shielding plate reaches the first position from the second position, and at least the position of the shielding plate immediately before the movement is abnormal. It is characterized by detecting this .

  In the case of a general fluorescent X-ray analyzer, the excitation beam is a primary X-ray, but the excitation beam is not limited to this and may be an electron beam.

  In the X-ray analyzer according to the present invention, the second position is the home position of the shielding plate, and a predetermined number of pulses are given to the pulse motor for each aperture from the state where the shielding plate is at the home position. Thus, the shielding plate is moved by the drive mechanism so that the target aperture hole is positioned (that is, set) at a position where the excitation ray or the X-ray can pass. In other words, the shield plate can be returned to the home position by applying a predetermined number of pulses corresponding to the aperture in a state where a certain aperture is set.

  When the movement control means is instructed to change the restriction hole, the number of pulses corresponding to the restriction hole before the change is given to the pulse motor to temporarily return the shielding plate to the home position. The shielding plate is moved until it is obtained. However, if the shielding plate is displaced due to out-of-step, etc., the shielding plate will return to the home position even if the number of pulses corresponding to the aperture hole before the change is applied to the pulse motor as described above. Dont return. Therefore, when the shielding plate is subsequently moved from the home position to the first position, the number of pulses corresponding to the distance between the home position and the first position is considerably different (small in some cases is large). The shielding plate does not reach the first position unless it is given a pulse.

  Therefore, the abnormality detection means counts the number of pulses until the shielding plate moves from the home position (actually recognized as the home position) to the first position, and the counted value falls within a specified range. If not, it is determined that the position of the shielding plate immediately before changing the aperture is abnormal, that is, there is a positional shift. As a result, it is recognized that at least the most recently acquired data is not acquired under an appropriate restriction condition, and this is notified to the user to prompt the rejection of unreliable data or automatically. Data can be rejected. The above-mentioned specified range is centered on the number of pulses corresponding to the distance between the home position and the first position, taking into account variations in position detection by the position detection means and mechanical play such as a drive mechanism. You only have to decide in advance.

Further , according to the X-ray analysis apparatus of the present invention, even when the aperture is not changed, the abnormality detection of the positional deviation of the shielding plate is performed every predetermined number of times of analysis. Therefore, even in applications where analysis is often performed repeatedly under the same aperture conditions, the reliability of the data can be improved by detecting an abnormality in the position of the shielding plate.

  Usually, the drive mechanism and the position detection means are originally provided in the X-ray analyzer, and the functions of the movement control means and the abnormality detection means can be realized by a program operated on the CPU. Therefore, according to the X-ray analysis apparatus of the present invention, the position shift of the shielding plate can be achieved by changing or adding a program without adding troublesome hardware or greatly changing existing hardware. That is, it is possible to detect problems such as setting of an unintended diaphragm hole or a portion that is not a diaphragm hole on the optical axis of excitation rays or X-rays. Thereby, data acquired in a defective state can be excluded, and reliability of data can be ensured. For this reason, it is possible to avoid making a large change in the apparatus and to avoid a significant increase in cost. It is also possible to add the above functions only by updating the program of the conventional apparatus.

  A fluorescent X-ray analyzer according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a detection unit of an energy dispersive X-ray fluorescence analyzer according to the present embodiment, and FIG. 2 is a schematic configuration diagram of an X-ray irradiation region aperture switching mechanism and circuit in the X-ray fluorescence analyzer of the present embodiment. It is.

As shown in FIG. 1, when the sample 2 is irradiated with the primary X-rays emitted from the X-ray tube 1, the sample 2 is excited by the primary X-rays to emit fluorescent X-rays. The fluorescent X-ray is introduced, for example, in Li Ji um drift Si detector semiconductor detector 3, such as, and the intensity is detected fluorescent X-rays of energy (wavelength). Between the X-ray tube 1 and the sample 2, an X-ray shielding plate 4 having an aperture for limiting the X-ray irradiation region 2a on the sample 2 is interposed.

  As shown in FIG. 2, the X-ray shielding plate 4 is formed by providing a plurality of (four in this example) throttle holes 4 a to 4 d with different inner diameters in an elongated plate-like member. The rotation operation by the drive mechanism 14 including the pulse motor (stepping motor) is converted into a linear operation by the transmission mechanism 15 including the rack and pinion, whereby the X-ray shielding plate 4 has the same direction as the arrangement direction of the aperture holes 4a to 4d. It is possible to reciprocate linearly. The pulse motor is operated by a pulse signal sent from the control unit 10. The control unit 10 is provided with an input unit 11 for setting the throttle holes 4a to 4d to be used by the user for analysis, and a display unit 12 for notifying the selection status of the throttle holes and for notifying operation abnormality. Yes. Further, the sensor 13 as position detecting means in the present invention detects that the X-ray shielding plate 4 has reached a predetermined origin position (first position in the present invention) P1. In the present embodiment, a photo sensor is used, but this may be a mechanical switch, a magnetic sensor, or the like.

  The control unit 10 is configured mainly with a microcontroller including a CPU, RAM, ROM, etc., and the CPU executes a control program stored in advance in the ROM, thereby achieving characteristic abnormality detection processing as described later. Is done.

  In the fluorescent X-ray analyzer, the sample to be analyzed is automatically and sequentially exchanged by a sample exchange mechanism (not shown), and one or more specific elements contained in the sample are quantified, and the quantification result is recorded. Further, the pass / fail of the sample (for example, rejected when the amount of the impurity element is equal to or greater than the threshold value) is determined by comparing the quantitative value with a predetermined threshold value. The user can instruct in advance the type of the throttle holes 4a to 4d to be used as analysis conditions for each analysis of one sample.

  When the apparatus is activated after the power is turned on, the control unit 10 executes initialization of the apparatus. The X-ray irradiation area stop switching mechanism is initialized according to the flowchart shown in FIG. That is, first, the control unit 10 sends a pulse signal to the pulse motor, and moves the X-ray shielding plate 4 in the direction of the origin position P1 (step S1). When the controller 10 recognizes that the X-ray shielding plate 4 has reached the origin position P1 based on the detection signal from the sensor 13 (Yes in step S2), it further sends a pulse signal to the pulse motor by a specified number N (step S2). S3). Thereby, the X-ray shielding plate 4 stops at a position moved from the origin position P1 by a distance corresponding to a prescribed number N of pulse signals. This stop position is defined as a home position P2.

  4 and 5 are flowcharts of the control operation for the X-ray irradiation region stop switching mechanism when the stop hole is selected in the analysis.

When an aperture selection instruction is made (step S11), the control unit 10 first determines whether or not the aperture hole selected and instructed is the same as the aperture set at that time (step S12). For example, when the aperture hole 4d having the maximum aperture diameter is currently set and the aperture holes 4a to 4c having other aperture diameters are instructed to be selected, it is determined No in step S12. Then, the control unit 10 performs an aperture switching operation accompanied by an aperture hole position abnormality detection operation (step S30).

  That is, first, in order to once return the X-ray shielding plate 4 to the home position P2, a predetermined number of pulse signals corresponding to the aperture set at that time are sent to the pulse motor (step S31). . Thereafter, until it is recognized by the detection signal from the sensor 13 that the X-ray shielding plate 4 has reached the origin position P1 (Yes in step S33), the pulse signal is sent to the pulse motor while counting the number of pulse signals. (Step S32).

  The control unit 10 acquires the count value n of the pulse signal when it is recognized as the origin position P1 (step S34), and calculates the difference Δ between the count value n and the specified number N (step S35). Since the count value n is the number of pulse signals required for the X-ray shielding plate 4 to move between the home position P2 and the origin position P1, the position returned by the control in step S31 is the original home position P2. If there is, the count value n and the specified number N match, and the difference Δ should be zero. However, in actuality, the position detection by the sensor 13 has a certain amount of error, and the drive mechanism 14 and the transmission mechanism 15 have mechanical play (play). Does not match exactly. Therefore, in consideration of such backlash and position detection error, an allowable value of the difference Δ is determined in advance.

  The control unit 10 determines whether or not the calculated difference Δ is less than or equal to an allowable value (step S36). If the calculated difference Δ is less than or equal to the allowable value, the X-ray shielding plate 4 is returned to the home position P2 and further selected. By sending the number of pulse signals corresponding to the holes to the pulse motor, the selection-designated throttle hole is set (step S37). Then, the control unit 10 outputs a display indicating that the instructed aperture is set to the display unit 12 (step S38). As a result, the next analysis using the selected and designated aperture is possible. Thereafter, the number m of repeated selections described later is reset to zero (step S39).

  On the other hand, when the difference Δ calculated in step S35 exceeds the allowable value, it is considered that the position returned by the control in step S31 is not the original home position P2. That is, the type of the throttle hole that the control unit 10 grasped at that time is different from the throttle hole that was actually set, or the X-ray hits a place that is not the throttle hole, etc. It means that there is a possibility. That is, it can be considered that the X-ray shielding plate 4 is displaced due to slippage (step-out) during operation of the driving mechanism 14 or the transmission mechanism 15 or disturbance. Therefore, the control unit 10 outputs an error display indicating that the operation is abnormal to the display unit 12 (step S40). In this case, since the data obtained with the same aperture setting immediately before and before that is not reliable, the user who viewed the error display takes measures such as rejecting the already acquired data. Of course, it is also possible to perform a display instructing to reject the data more directly.

  When it is determined in step S12 that the aperture specified for selection is the same as the aperture set at that time, the control unit 10 increments the number m of repeated selections (step S13) and repeats. It is determined whether the number of selections m is less than a predetermined number of times M (step S14). Here, the prescribed number M is appropriately determined as will be described later. If the repetitive selection number m is less than the prescribed number M, the control unit 10 outputs a display indicating that the designated aperture is set to the display unit 12 (step S25). That is, in this case, the abnormality detection operation described later is not performed.

  When the number m of repeated selections reaches the specified number M, an abnormality detection operation similar to that at the time of the above-described aperture switching operation is performed although it is not necessary to change the aperture (step S15). That is, in order to return the X-ray shielding plate 4 to the home position once, a predetermined number of pulse signals corresponding to the aperture set at that time are sent to the pulse motor (step S16). Thereafter, until it is recognized by the detection signal from the sensor 13 that the X-ray shielding plate 4 has reached the origin position P1 (Yes in step S18), the pulse signal is sent to the pulse motor while counting the number of pulse signals. (Step S17).

  The control unit 10 acquires the count value n of the pulse signal when it is recognized as the origin position P1 (step S19), and calculates the difference Δ between the count value n and the specified number N (step S20). The specified number N is the same as the specified number N in step S35. The control unit 10 determines whether or not the calculated difference Δ is less than or equal to an allowable value (step S21). If the calculated difference Δ is less than or equal to the allowable value, the X-ray shielding plate 4 is returned to the home position and further selected and designated aperture holes. The number of pulse signals corresponding to is sent to the pulse motor, so that the selection-instructed (not actually switched) aperture hole is set (step S22). Then, the control unit 10 outputs a display indicating that the instructed aperture is set to the display unit 12 (step S23). Then, the selection repetition number m is reset to zero (step S24).

  On the other hand, when the difference Δ calculated in step S20 exceeds the allowable value, it is considered that the position returned by the control in step S16 is not the original home position P2. Therefore, the control unit 10 outputs an error display indicating that the operation is abnormal to the display unit 12 (step S26). In this case, since the data obtained after the most recent abnormality detection operation is not reliable, the user who viewed the error display takes measures such as rejecting the already acquired data. Of course, it is also possible to perform a display instructing to reject the data more directly.

  When an instruction to change the aperture is made, the process of steps S30 to S36 detects abnormality immediately before (that is, before) the change of the aperture. On the other hand, if the aperture is not changed, it is not necessary to move the X-ray shielding plate 4 originally. However, as a general usage pattern of the fluorescent X-ray analyzer, the same aperture (usually the aperture having the largest aperture area) is often used repeatedly, and the case of changing the aperture, that is, No in step S12. There are relatively few cases that are judged. Therefore, if no abnormality detection operation is performed when the aperture is not changed, even if the X-ray shielding plate 4 is misaligned, this is not detected and inappropriate data is detected over a long period of time. May continue to be acquired.

  On the other hand, according to the processing of steps S13 to S21 shown in FIG. 4, even when the aperture is not changed at all, the abnormality detection operation is performed every specified number of times M. Therefore, even if the X-ray shielding plate 4 is misaligned, the data to be rejected is only the prescribed number of times M going back in the past, and the reliability of the past data is further guaranteed. For this reason, if the value of the specified number of times M is reduced, the amount of data to be rejected when the X-ray shielding plate 4 is displaced is small. On the other hand, if the value of the specified number of times M is reduced, the frequency of executing the processing of steps S16 to S24 increases despite the fact that the aperture is not changed, and the time required for analysis is increased accordingly, and the throughput is reduced. In addition, the number of operations of the drive mechanism 14 and the transmission mechanism 15 increases, so that the consumption of parts is accelerated. Therefore, the predetermined number of times M may be determined in advance in consideration of this. For example, when it is assumed that analysis is performed about 100 times a day, the prescribed number M may be set to 100.

  In the description of the above embodiment, the detection of the abnormality of the aperture switching mechanism that limits the X-ray irradiation region has been described. However, in the fluorescent X-ray analyzer, the observation target is between the sample 2 and the detector 3. A switching mechanism having the same structure as described above may be used to provide a stop for limiting the field of view and change the aperture area of the stop. Even in such a case, it is obvious that the abnormality detection as described above can be used and is effective.

  Furthermore, in addition to those that emit fluorescent X-rays by irradiating the sample with primary X-rays, X-rays that emit fluorescent X-rays by irradiating the sample with other excitation rays such as electron beams and ion beams Of course, the present invention can also be applied to an analyzer. It is also apparent that the present invention can be applied not only to an energy dispersive X-ray analyzer but also to a wavelength dispersive X-ray analyzer.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the detection part of the energy dispersive X-ray fluorescence spectrometer which is one Example of this invention. The schematic block diagram of the X-ray irradiation area | region aperture switching mechanism and circuit in the fluorescent X-ray-analysis apparatus of a present Example. The flowchart of the initialization operation | movement of the X-ray irradiation area | region aperture switching mechanism in the fluorescent X-ray-analysis apparatus of a present Example. The flowchart of control operation | movement of the X-ray irradiation area | region aperture switching mechanism when an aperture is selected in the fluorescent X-ray analyzer of a present Example. The flowchart of control operation | movement of the X-ray irradiation area | region aperture switching mechanism when an aperture is selected in the fluorescent X-ray analyzer of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... Sample 2a ... X-ray irradiation area | region 3 ... Semiconductor detector 4 ... X-ray shielding board 4a-4d ... Diaphragm hole 10 ... Control part 11 ... Input part 12 ... Display part 13 ... Sensor 14 ... Drive mechanism 15 ... Transmission mechanism

Claims (1)

An X-ray analyzer that irradiates a sample with excitation rays emitted from an excitation source and introduces X-rays emitted from the sample into a detector, and is disposed between the excitation source and the sample In an X-ray analysis apparatus comprising either a region limiting unit for limiting an irradiation region of excitation rays or a region limiting unit for limiting a visual field region disposed between a sample and a detector,
a) a shielding plate provided with a plurality of apertures of different sizes as the region limiting portion;
b) a drive mechanism including a pulse motor for moving the shielding plate to selectively move the aperture hole on the optical axis of the excitation line or X-ray;
c) position detecting means for detecting that the shielding plate has reached the first position;
d) Along with the change of the aperture hole, after applying the number of pulses corresponding to the aperture hole before the change to the pulse motor to return the shielding plate to the second position, a detection signal by the position detection means is further generated. Movement control means for moving the shielding plate by applying pulses to the pulse motor until obtained;
e) In the movement control by the movement control means, the number of pulses until the shielding plate comes from the second position to the first position is counted, and the count value is used to immediately before the change of the aperture hole. An abnormality detecting means for detecting that the position of the shielding plate is abnormal;
With
The movement control means provides the pulse motor with the number of pulses corresponding to the aperture for each predetermined number of analysis executions even when the aperture is not changed, so that the shielding plate is moved to the second position. After returning, further moving the shielding plate by giving a pulse to the pulse motor until a detection signal by the position detection means is obtained,
In the movement control, the abnormality detection means uses a count value of pulses until the shielding plate reaches the first position from the second position, and at least the position of the shielding plate immediately before the movement is abnormal. An X-ray analyzer characterized by detecting that

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