JP6873125B2 - X-ray generator and analyzer equipped with it - Google Patents

Description

The present invention relates to an X-ray generator that emits characteristic X-rays, and more particularly to an analyzer that includes an X-ray generator.

With the diversification and quality improvement of steel varieties (for example, low alloy steel, carbon steel, stainless steel, low cast iron, etc.) and non-ferrous metal varieties, and the development of steelmaking processing technology, base materials (eg, Fe, Cu, Al Etc.) It has been required to strictly control the amount of trace components contained in, especially elements such as C, Si, S, P, Mn, Ni, etc., and production plants for steel materials, non-ferrous metal materials, etc. In the steelmaking / refining process such as, it is becoming important to quantify the trace components contained in the base metal.
Therefore, in recent years, by irradiating a sample with characteristic X-rays and detecting the intensity of fluorescent X-rays excited and emitted by the characteristic X-rays, fluorescent X-rays are used to perform qualitative and quantitative analysis of the elements contained in the sample. Analyzers are becoming widely used in production plants and the like.

FIG. 4 is a diagram showing the configuration of a fluorescent X-ray analyzer, and FIG. 5 is a circuit diagram of the X-ray generator 101 shown in FIG. The fluorescent X-ray analyzer 160 includes an X-ray generator 101, a sample table 61 on which the sample S is arranged, a detector 62 for detecting the energy and intensity of fluorescent X-rays, an input device 71, a CPU 172, and the like. The computer 170 is provided.

The X-ray generator 101 applies an X-ray tube 10 that emits characteristic X-rays, a high-voltage generation DC power supply (high-voltage power supply) 20 for applying a _{high-voltage V high , and a low-voltage V low.} Filament power supply (low voltage power supply) 30, tube voltage control circuit (high voltage power supply control circuit) 140 that controls the high voltage generation DC power supply 20, and filament current control circuit (low voltage power supply control circuit) that controls the filament power supply 30. ) 150 (see, for example, Patent Document 1).

FIG. 6 is a cross-sectional view of the X-ray tube 10 shown in FIG. The X-ray tube 10 includes a target 11 as an anode, a filament 12 as a cathode, and a substantially cylindrical housing 13 having the target 11 and the filament 12 inside.

A circular exit window 13a is formed on the side wall of the housing 13, an end face 11a of the target 11 is arranged at a position facing the exit window 13a, and a filament is arranged at a position facing the end face 11a of the target 11. 12 are arranged. Then, the filament power supply 30 and the filament current control circuit 150 are connected to the filament 12 via the low voltage cable 16. Further, the high voltage generating DC power supply 20 and the tube voltage control circuit 140 are connected to the target 11 via the high voltage cable 15. Further, the negative electrode of the high voltage generation DC power supply 20 is connected to one end of the filament 12.

The tube voltage control circuit 140 applies a _{high voltage V high} to the target 11 based on the input signal from the input device 71. _{For example, when the analyst selects the tube voltage value V high} from the voltage values of about 1 kV to 50 kV using the input device 71, the tube voltage control circuit 140 _{applies the selected tube voltage value V high} to the target 11. As a result, the potential of the target 11 is set to the tube voltage value V _high . At this time, the tube voltage control circuit 140 performs feedback control so that _{the potential of the target 11 does not deviate from the tube voltage value V high.}

The filament current control circuit 150 applies a _{low voltage V low} to the filament 12 based on an input signal from the input device 71. For example, when the analyst selects the tube current value I from the current values of about 5 mA to 100 mA using the input device 71, the filament current control circuit 150 does not deviate from the selected tube current value I. Feedback control is performed to pass a filament current through 12.

According to such an X-ray generator 101, when an input signal for performing analysis is input, a high voltage V _high is applied to the target 11 as shown in FIG. 5A, and the potential of the target 11 is reached. Is set to the tube voltage value V _high, and a low voltage V _low is applied to the filament 12 to allow a filament current to flow, thereby accelerating the thermoelectrons e radiated from the filament 12 and causing them to collide with the end face 11a of the target 11. As a result, the characteristic X-ray generated at the end surface 11a of the target 11 is emitted from the emission window 13a. The intensity and energy of this characteristic X-ray are _{controlled by changing the tube voltage value V high} and the tube current value I.

Japanese Unexamined Patent Publication No. 2007-165081

By the way, in order to stop the X-ray generator 101 after the analysis is completed, the application of the _{low voltage V low} to the filament 12 is stopped, and then the application of the _{high voltage V high to the target 11 is stopped.} , It is necessary to reduce the potential of the target 11 from the tube voltage value V _high to 0 V, but the waiting time for the potential of the target 11 to decrease to 0 V was long (for example, the _{rate of decrease of the tube voltage value V high} is 1.8 kV / s). ).

Since the filament current control circuit 150 performs feedback control so as not to deviate from the tube current value I, when the tube current stops flowing, the filament current becomes the maximum value and the temperature of the filament 12 becomes the maximum temperature. .. The higher the temperature of the filament 12, the more the filament 12 is consumed, so that the life of the filament 12 is shortened. Therefore, when the input signal "OFF" for stopping the X-ray generator 101 is input, the filament current control circuit 150 _{stops applying the low voltage V low} to the filament 12, and then the tube voltage control circuit. 140 has stopped applying the high voltage V _{high to the target 11.}

The applicant examined a method for lowering the potential of the target 11 in a short time. Low voltage V on filament 12_lowAfter stopping the application of high voltage V to the target 11. _highBy stopping the application of, as shown in FIG. 5 (b), the tube voltage value V is caused by the extremely small current i flowing through the resistance of the insulator of the housing 13 and the high voltage cable 15._{high h}Is missing.

Therefore, as shown in FIG. 7, a high withstand voltage resistor and a switch are provided, and when the input signal “OFF” is input _{, the application of the low voltage V low} to the filament 12 is stopped, and then the high voltage V is applied to the target 11. to stop applying the _high, by connecting the high-voltage resistor and the target 11 by the switch, it is conceivable to escape the tube voltage value V _high. However, it is necessary to provide parts such as high withstand voltage resistors and switches.

Therefore, when stopping the X-ray generator 101, instead of first setting the tube current value I to 0A, a filament current of an appropriate predetermined value (0.3A or more and 5.0A or less) is passed through the filament 12. It was found that by irradiating the target 11 with thermions e', the tube voltage value V _high is released as the tube current I'(see FIG. 2B). As a result, the rate of decrease in the tube voltage value _{V hig h} is 3.0 kV / s, and the became faster.

That is, the X-ray generator of the present invention has a housing, a target which is an anode arranged inside the housing, and a filament which is a cathode arranged inside the housing. An X-ray tube that receives thermoelectrons emitted from the target and emits X-rays generated by the target, a high-voltage power supply for applying a high voltage to the target, and a low voltage to the filament. Controls a low-voltage power supply for applying, a high-voltage power supply control circuit for controlling the high-voltage power supply, an input device capable of inputting an OFF signal for stopping the X-ray generator, and the low-voltage power supply. An X-ray generator including a low-voltage power supply control circuit to which an OFF signal for stopping the X-ray generator is input, and the high-voltage power supply control circuit when the OFF signal is input. Stops applying the high voltage to the target, and then the low voltage power supply control circuit applies the low voltage of a predetermined value to the filament for a predetermined time.

According to the X-ray generator of the present invention, _{in order to reduce the tube voltage value V high} of the target potential, the tube voltage value V _high of the target potential is released as the tube current I', so that the tube voltage value V _high is set. The waiting time for escape can be shortened. In addition, no mechanism or component (high withstand voltage resistor or switch) for switching circuits is required.

(Means and effects to solve other problems)
Further, in the above invention, the predetermined time may be a time for the potential of the target to decrease.

Further, in the above invention, the low voltage of the predetermined value may be for passing a filament current of 0.3 A or more and 5.0 A or less through the filament.
The filament current of 0.3 A or more and 5.0 A or less prevents the filament from being consumed when the filament temperature becomes an appropriate temperature.

The analyzer of the present invention provides an X-ray CT apparatus as described above, may be Ru analyzer and a detector.

The figure which shows the structure of the fluorescent X-ray analyzer which concerns on embodiment. The circuit diagram of the X-ray generator shown in FIG. A flowchart for explaining how to stop. The figure which shows the structure of the fluorescence X-ray analyzer. The circuit diagram of the X-ray generator shown in FIG. FIG. 4 is a cross-sectional view of the X-ray tube shown in FIG. Circuit diagram of the X-ray generator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It goes without saying that the present invention is not limited to the embodiments described below, and various aspects are included without departing from the spirit of the present invention.

FIG. 1 is a diagram showing a configuration of a fluorescent X-ray analyzer according to an embodiment, and FIG. 2 is a circuit diagram of the X-ray generator shown in FIG. The same reference numerals are given to those similar to the fluorescent X-ray analyzer 160.
The fluorescent X-ray analyzer 60 includes an X-ray generator 1, a sample table 61 on which the sample S is arranged, a detector 62 for detecting the energy and intensity of fluorescent X-rays, an input device 71, a CPU 72, and the like. The computer 70 is provided.

The X-ray generator 1 applies an X-ray tube 10 that emits characteristic X-rays, a high-voltage generation DC power supply (high-voltage power supply) 20 for applying a _{high-voltage V high , and a low-voltage V low.} Filament power supply (low voltage power supply) 30, tube voltage control circuit (high voltage power supply control circuit) 40 that controls the high voltage generation DC power supply 20, and filament current control circuit (low voltage power supply control circuit) that controls the filament power supply 30. ) 50.

The filament current control circuit 50 applies a _{low voltage V low} to the filament 12 based on an input signal from the input device 71. For example, when the analyst selects the tube current value I from the current values of about 5 mA to 100 mA using the input device 71, the filament current control circuit 50 does not deviate from the selected tube current value I. Feedback control is performed to pass a filament current through 12.
Further, in the filament current control circuit 50 according to the embodiment, when the input signal “OFF” for stopping the X-ray generator 1 is input, the filament 12 has a predetermined time (for example, 20 seconds or less) and a predetermined value. by applying a low voltage _{V low} 'of, and for channeling the filament current of a predetermined value (0.3 a or 5.0A or less).
The predetermined value may be 0.3 A or more and 5.0 A or less, but in the fluorescent X-ray analyzer 60, it was set to 3.4 A in consideration of the circuit configuration. As a result, the reduction speed also changes depending on the structure of the X-ray tube 10, but in the fluorescent X-ray analyzer 60, 50 kV (maximum tube voltage) / 3 kV (decrease speed per second) = 16.6 s, which is 16.6. The potential began to drop in seconds.

The tube voltage control circuit 40 applies a _{high voltage V high} to the target 11 based on the input signal from the input device 71. _{For example, when the analyst selects the tube voltage value V high} from the voltage values of about 1 kV to 50 kV using the input device 71, the tube voltage control circuit 40 _{applies the selected tube voltage value V high} to the target 11. As a result, the potential of the target 11 is set to the tube voltage value V _high . At this time, the tube voltage control circuit 40 performs feedback control so that _{the potential of the target 11 does not deviate from the tube voltage value V high.}
Further, the tube voltage control circuit 40 according to the embodiment does not stop applying the _{low voltage V low'to the} filament 12 when the input signal “OFF” for stopping the X-ray generator 1 is input. In addition, the application of the high voltage V _high to the target 11 is stopped.

Here, a stop method for stopping the X-ray generator 1 will be described. FIG. 3 is a flowchart for explaining a stop method.
First, in the process of step S101, the CPU 72 determines whether or not the input signal "OFF" for stopping the X-ray generator 1 has been input. When it is determined that the input signal "OFF" has not been input, the process of step S101 is repeated.

On the other hand, when the input signal "OFF" is determined to have been input, the process of step S102, the filament current control circuit 50, by applying a low voltage V _{lo w 'of} predetermined value to the filament 12, a predetermined value (3 .4A) Filament current is applied. At this time, since the temperature of the filament 12 does not reach the maximum temperature, it is possible to prevent the filament 12 from being consumed.
Next, in the process of step S103, the tube voltage control circuit 40 stops applying the _{high voltage V high to the target 11.}

Next, in the process of step S104, the CPU 72 determines whether or not a predetermined time (20 seconds) has elapsed. When it is determined that the predetermined time has not elapsed, the process of step S104 is repeated. At this time, the tube voltage value V _high escapes as the tube current I'(see FIG. 2B).
Next, when it is determined that the predetermined time has elapsed, in the process of step S105, the filament current control circuit 50 stops applying _{the low voltage V low'of a predetermined value to the filament 12.}
Then, when the process of step S105 is completed, this flowchart is terminated.

As described above, according to the fluorescent X-ray analyzer 60 according to the present invention, _{in order to reduce the tube voltage value V high} of the potential of the target 11, the tube voltage value V _high of the potential of the target 11 is set to the tube current I'. Therefore, the waiting time for _releasing the tube voltage value V high can be shortened.

<Other Embodiments>
(1) In the above-described embodiment, the fluorescent X-ray analyzer 60 has been described as an example, but the present invention also applies to an apparatus that continuously generates X-rays (non-destructive inspection apparatus, medical X-ray apparatus, etc.). The invention can be applied in the same way. Further, since the maximum tube voltage varies depending on the device, the explanation was given using the fluorescent X-ray analyzer 60, which uses a relatively low tube voltage for surface analysis, as an example. May be applied.

(2) The fluorescent X-ray analyzer 60 described above has a configuration for determining whether or not a predetermined time (20 seconds) has elapsed, but whether the potential of the target 11 is equal to or less than a predetermined value (1 kV). It may be configured to determine whether or not.

The present invention can be used in a fluorescent X-ray analyzer or the like for calculating the concentration of an element contained in a sample.

1 X-ray generator 10 X-ray tube 11 Target 12 Filament 13 Housing 15 High-voltage cable 16 Low-voltage cable 20 High-voltage power supply 30 Low-voltage power supply 40 High-voltage power supply control circuit 50 Low-voltage power supply control circuit

Claims (4)

The target has a housing, a target which is an anode arranged inside the housing, and a filament which is a cathode arranged inside the housing, and receives thermoelectrons radiated from the filament at the target. Then, an X-ray tube that emits X-rays generated at the target and
A high-voltage power supply for applying a high voltage to the target,
A low-voltage power supply for applying a low voltage to the filament,
The high-voltage power supply control circuit that controls the high-voltage power supply and
An input device that can input an OFF signal to stop the X-ray generator,
The low voltage power supply is feedback-controlled so that there is no discrepancy between the tube current value flowing through the X-ray tube and the selected tube current value, and an OFF signal for stopping the X-ray generator is input. An X-ray generator equipped with a voltage power supply control circuit.
When the OFF signal is input, the high voltage power supply control circuit stops applying a high voltage to the target, and then the low voltage power supply control circuit stops the feedback control for a predetermined time on the filament. , An X-ray generator characterized by applying a low voltage of a predetermined value. The X-ray generator according to claim 1, wherein the predetermined time is a time for the potential of the target to decrease. The X-ray generator according to claim 1, wherein the low voltage of the predetermined value is for passing a filament current of 0.3 A or more and 5.0 A or less through the filament. An analyzer including the X-ray generator according to claim 1 and a detector.

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