JP5135601B2 - X-ray tube and X-ray analyzer - Google Patents

Description

  The present invention relates to an X-ray tube and an X-ray analyzer suitable for a handy type and a portable type which are used for an energy dispersive fluorescent X-ray analyzer, for example, and are small and light.

  X-ray fluorescence analysis irradiates a sample with primary X-rays emitted from an X-ray source, and detects the fluorescent X-rays emitted from the sample with an X-ray detector. Acquire and perform qualitative analysis or quantitative analysis of the sample. This fluorescent X-ray analysis is widely used in processes and quality control because samples can be analyzed quickly and non-destructively.

This fluorescent X-ray analysis can be performed using a wavelength dispersion method in which fluorescent X-rays are dispersed with a spectroscopic crystal and the wavelength and intensity of the X-rays are measured. There are energy dispersion methods for measuring the energy and intensity of X-rays.
Conventionally, in Patent Document 1, for example, in order to increase the sensitivity of fluorescent X-rays, an X-ray tube and an X-ray analyzer are provided by providing an extraction window for extracting fluorescent X-rays that have passed through the X-ray tube. Attempts have been made to approach the sample.
Further, as described in Patent Document 2, a handy type energy dispersive X-ray fluorescence analyzer has become widespread due to miniaturization of the X-ray tube and the X-ray analyzer.

JP-A-8-115694 Japanese Patent No. 3062685

The following problems remain in the conventional technology.
For example, in the X-ray analysis apparatus described in Patent Document 1, the effect of increasing the detection sensitivity by bringing the X-ray tube and the X-ray detector closer to the sample is great, but the X-ray tube and the X-ray detector are finite, respectively. Since it has a certain size or more, there is a limit to the proximity.
Further, in the conventional handy type energy dispersive X-ray fluorescence analyzer, further miniaturization and weight reduction are demanded, but as an apparatus configuration, an X-ray tube and an X-ray detector are mostly in volume and mass. Therefore, the conventional form has a limit in reducing the size and weight. Furthermore, the handy type is an open type that directly irradiates primary X-rays to the sample in the atmosphere instead of storing the sample in a sealed sample chamber for analysis. Since the amount of X-ray generation from the tube is limited, it is necessary to detect fluorescent X-rays from the sample more efficiently.

  The present invention has been made in view of the above-described problems, and can be further reduced in size and weight, and an X-ray tube capable of detecting fluorescent X-rays and the like more efficiently and increasing sensitivity. An object is to provide an X-ray analyzer.

  The present invention employs the following configuration in order to solve the above problems. That is, the X-ray tube of the present invention includes a vacuum housing having a window portion formed of an X-ray permeable film that is evacuated and capable of transmitting X-rays, and an electron beam installed in the vacuum housing. An electron beam source that emits, a target that is irradiated with the electron beam to generate primary X-rays, and that the primary X-rays can be emitted to an external sample through the window portion; X-ray detection that is arranged in the vacuum housing so as to detect fluorescent X-rays and scattered X-rays emitted from the sample and incident from the window, and outputs a signal including energy information of the fluorescent X-rays and scattered X-rays And an element.

  In this X-ray tube, the X-ray detection element, which is a constituent element of the X-ray detector, is arranged in the vacuum casing so as to be able to detect fluorescent X-rays and scattered X-rays incident from the window portion. Is integrally housed in a vacuum housing together with an electron beam source and a target which are constituent elements of an X-ray tube, so that the entire apparatus can be further reduced in size and weight. In addition, since the X-ray detection element is arranged in the vacuum housing and can be detected in close proximity to the sample together with the target that generates primary X-rays, excitation and detection can be performed very efficiently. Become. Furthermore, if it is applied to an open type handy type, efficient detection is possible, so even if the X-ray generation amount is further suppressed, detection can be performed with high sensitivity, and high safety can be obtained.

  In the X-ray tube of the present invention, the target is disposed in proximity to or in contact with the window portion, and a light receiving surface of the X-ray detection element is disposed around the target. . That is, in this X-ray tube, since the light-receiving surface of the X-ray detection element is arranged around the target, when the analysis is performed in a state where the sample is brought close to the window, the sample is obtained by primary X-rays from the target. X-rays generated from the X-ray can be efficiently detected by an X-ray detection element arranged around the target (ie, near the window).

  In the X-ray tube of the present invention, the X-ray detection element is disposed in a region between the electron beam source and the target and has a transmission hole through which the electron beam can pass. And That is, in this X-ray analyzer, the target is irradiated with an electron beam through a transmission hole of an X-ray detection element arranged between the electron beam source and the target. Can be irradiated.

  The X-ray tube of the present invention is characterized in that at least one of the target and the window is set to a ground potential or a positive potential. That is, in this X-ray tube, since at least one of the target and the window is set to the ground potential or the positive potential, the X-ray detection element can be obtained by pulling secondary electrons from the target back to the target or the window by an electric field. The secondary electrons can be prevented from entering.

  Further, the X-ray tube of the present invention is characterized in that a shutter capable of moving forward and backward in the electron beam path is provided between the electron beam source and the target. That is, in this X-ray tube, since a shutter capable of moving forward and backward in the electron beam path is provided between the electron beam source and the target in the tube, the X-ray is more than in the case of providing a shutter in the primary X-ray path. The generation point (target) and the sample can be brought closer to each other. Further, by making the shutter closed until the electron beam, which is a thermal electron from the electron beam source, is stabilized, and opening the shutter after stabilization, measurement with a stable electron beam becomes possible.

  The X-ray tube of the present invention is characterized in that a shielding body for blocking radiant heat from the electron beam source is disposed between the electron beam source and the X-ray detection element. That is, in this X-ray tube, since the shield is provided between the electron beam source and the X-ray detection element, the radiant heat from the generated electron beam source is cut off and the radiant heat for cooling the X-ray detection element is used. Adverse effects can be suppressed.

  An X-ray analysis apparatus according to the present invention includes the X-ray tube according to the present invention, an analyzer that analyzes the signal, and a display unit that displays an analysis result of the analyzer. That is, since this X-ray analysis apparatus includes the X-ray tube of the present invention, the entire apparatus can be miniaturized.

  Moreover, the X-ray analyzer of the present invention is characterized in that the analyzer and the display unit are provided in the vacuum casing to be portable. That is, in this X-ray analyzer, since the analyzer and the display unit are integrally mounted in the vacuum casing, the analysis result can be confirmed on the spot by the analyzer and the display unit, and Small and lightweight handy type.

The present invention has the following effects.
That is, according to the X-ray tube and the X-ray analysis apparatus according to the present invention, the X-ray detection element is disposed in the vacuum casing so as to detect the fluorescent X-rays and the scattered X-rays incident from the window portion. The whole can be further reduced in size and weight, and excitation and detection can be performed more efficiently. In particular, when applied to an open-type handy type X-ray analyzer, even if the amount of X-ray generation is further suppressed, detection can be performed with high sensitivity, and high safety can be obtained.

  Hereinafter, an embodiment of an X-ray tube and an X-ray analyzer according to the present invention will be described with reference to FIGS. 1 and 2. In each drawing used for the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

  The X-ray analyzer according to this embodiment is a portable (handy type) energy dispersive X-ray fluorescence analyzer, and as shown in FIG. A vacuum housing 2 having a window portion 1 formed of a possible X-ray transmission film, an electron beam source 3 that is installed in the vacuum housing 2 and emits an electron beam e, and is irradiated with the electron beam e to be primary A target T installed in the vacuum casing 2 so as to generate X-ray X1 and emit the primary X-ray X1 to the external sample S through the window 1, and is emitted from the sample S and emitted from the window 1. An X-ray detection element 4 which is disposed in the vacuum housing 2 so as to detect incident fluorescent X-rays and scattered X-rays X2 and outputs a signal including energy information of the fluorescent X-rays and scattered X-rays X2, and the above signals An analyzer 5 for analysis and a display unit 6 for displaying an analysis result of the analyzer 5 are provided. An X-ray tube is configured with the vacuum casing 2, the electron beam source 3, the target T, and the X-ray detection element 4 as main components.

The vacuum housing 2 includes a front storage portion 2a whose inside is in a vacuum state, and a rear storage portion 2b which is separated by the front storage portion 2a and the partition wall 2c and whose inside is in an atmospheric pressure state. Yes.
The window portion 1 is formed of, for example, Be (beryllium) foil as an X-ray transmission film. Note that a primary filter that is a metal thin film or a metal thin plate such as Cu (copper), Zr (zirconium), or Mo selected according to the sample S may be attached to the front surface of the window portion 1. The window 1 and the target T are set to a ground potential or a positive potential in order to pull back secondary electrons generated and emitted by the interaction between the electron beam e incident on the target T and the target T. Since secondary electrons usually have an energy of about several eV, a ground potential or a positive potential is set so that an electric field is higher than this energy.

The electron beam source 3 includes a current-voltage control unit 8 that controls a voltage (tube current) between a filament 7 serving as a cathode and a target T serving as an anode and a current (tube current) of an electron beam e. I have. The electron beam source 3 is generated when thermoelectrons (electron beams) generated from a filament 7 serving as a cathode are accelerated by a voltage applied between the filament 7 and a target T serving as an anode and collide with the target T. The generated X-rays are generated as primary X-rays.
Moreover, you may employ | adopt the carbon nanotube instead of the filament 7 as a cathode.

As the target T, for example, W (tungsten), Mo (molybdenum), Cr (chromium), Rh (rhodium), or the like is employed. This target T is arranged close to or in contact with the window portion 1.
The X-ray detection element 4 is a semiconductor detection element such as a Si (silicon) element which is a pin structure diode, for example. When one X-ray photon enters the X-ray detection element 4, a current pulse corresponding to one X-ray photon is generated. The instantaneous current value of this current pulse is proportional to the energy of the incident fluorescent X-ray.

  As shown in FIGS. 1 and 2, the X-ray detection element 4 is disposed in a region between the filament 7 of the electron beam source 3 and the target T, and has a transmission hole 4a through which the electron beam e can be transmitted. ing. Further, the target T is arranged immediately below and close to the transmission hole 4 a, and the light receiving surface of the X-ray detection element 4 is arranged around the target T.

  The X-ray detection element 4 is set to be held at a constant temperature by a cooling mechanism (not shown) (for example, a cooling mechanism using liquefied nitrogen as a refrigerant or a cooling mechanism using a Peltier element). In addition, the X-ray detection element 4 can ensure original performance by cooling to about -30 to -100 degrees. Further, the X-ray detection element 4 is guarded around the transmission hole 4a by a metal plate or the like so that the primary X-ray X1 and the electron beam e do not enter the light receiving surface.

A metal guard member 10 is provided between the target T and the X-ray detection element 4 so that primary X-rays X1, secondary electrons and reflected electrons from the target T do not enter the X-ray detection element 4. Yes. The metal guard member 10 is fixed to the vacuum housing 2 by a support (not shown), and a transmission hole for the electron beam e is formed at the center so that the electron beam e can be transmitted. Further, the metal guard member 10 is set to a ground potential or a positive potential, similarly to the window portion 1 and the target T.
In addition, it can suppress that a thermoelectron (electron beam e) injects into the X-ray detection element 4 by setting the X-ray detection element 4 to a minus electric potential.

  Further, a shutter 11 that can advance and retreat in the path of the electron beam e is provided between the filament 7 of the electron beam source 3 and the target T. The shutter 11 is made of Ta, W, Cu or the like as a material capable of blocking the electron beam e, and is connected to a driving mechanism 12 such as a small motor or a solenoid. This drive mechanism 12 is connected to the CPU 9 and is controlled so that the shutter 11 is retracted from the path of the electron beam e only at the time of measurement and the target T is irradiated with the electron beam e. Further, the CPU 9 controls the shutter 11 to be in a closed state until the electron beam e, which is thermoelectron from the filament 7 of the electron beam source 3, is stabilized, and opens the shutter 11 after stabilization.

Further, between the electron beam source 3 and the X-ray detection element 4, a shield 13 having a hole for transmitting an electron beam e at the center is supported by the vacuum casing 2. The shield 13 is formed of a metal plate or a metal sheet having high thermal conductivity such as Cu. The shield 13 blocks the radiant heat from the electron beam source 3 and releases the heat to the vacuum casing 2. It is intended not to adversely affect the cooling.
The filament 7, the target T, the X-ray detection element 4, the metal guard member 10, the shutter 11, the drive mechanism 12, and the shield 13 are disposed in the front housing portion 2 a of the vacuum housing 2.

The analyzer 5 is an X-ray signal processing unit that converts a current pulse generated by the X-ray detection element 4 into a voltage pulse, amplifies the signal, obtains a pulse height of the voltage pulse from this signal, and obtains an energy spectrum. This is a wave height analyzer (multi-channel pulse height analyzer) to be generated.
The current / voltage control unit 8 and the analyzer 5 are connected to the CPU 9, and various controls are performed by setting.

The display unit 6 is, for example, a liquid crystal display device, and is connected to the CPU 9 and can display various screens according to not only the analysis result such as the energy spectrum but also the setting.
The analyzer 5, the current / voltage control unit 8 and the CPU 9 are provided in the rear housing part 2b of the vacuum casing 2, and the display unit 6 is provided with a display surface arranged on the outer surface of the rear housing part 2b. Yes. That is, the analyzer 5 and the display unit 6 are integrally provided in the vacuum housing 2.
Note that, among the above-described components, those requiring power supply and potential setting are all connected to a power supply unit (not shown).

  As described above, in the present embodiment, the X-ray detection element 4 is disposed in the vacuum casing 2 so as to be able to detect the fluorescent X-rays and the scattered X-rays X2 incident from the window portion 1. The whole apparatus can be further reduced in size and weight by being housed in the vacuum housing 2 together with the electron beam source 3 and the target T. In addition, since the X-ray detection element 4 is arranged in the vacuum casing 2 and can be detected in close proximity to the sample S together with the target T that generates the primary X-ray X1, excitation and detection are very efficient. It becomes possible to do. In particular, since efficient detection is possible by applying to an open handy type, even if the amount of X-ray generation is further suppressed, detection can be performed with high sensitivity and high safety can be obtained.

  In addition, since the light receiving surface of the X-ray detection element 4 is arranged around the target T, the sample is obtained by the primary X-ray X1 from the target T when the analysis is performed with the sample S in proximity to the window 1. The fluorescent X-rays and the like generated from S can be efficiently detected by the X-ray detection element 4 arranged around the target T (that is, near the window portion 1).

In addition, since the target is irradiated with the electron beam e through the transmission hole 4a of the X-ray detection element 4 disposed between the electron beam source 3 and the target T, the target is obtained by narrowing the electron beam e through the transmission hole 4a. T can be irradiated.
Further, since the metal guard member 10 is provided between the X-ray detection element 4 and the target T, it is possible to prevent secondary electrons generated at the target T from being incident on the X-ray detection element 4. . Moreover, it can suppress that the metal guard member 10 shields the radiant heat from a target peripheral part, and exerts a bad influence on cooling of the X-ray detection element 4. FIG.

  Furthermore, since the metal guard member 10 is set to the ground potential or the positive potential, the secondary electrons from the target T are attracted to the metal guard member 10 by the electric field, and a higher blocking effect can be obtained.

In addition, since the target T and the window portion 1 are set to the ground potential or the positive potential, the secondary electrons from the target T are pulled back to the target T and the window portion 1 by an electric field, so The incidence of secondary electrons can be suppressed.
In addition, since a shutter 11 that can advance and retreat in the path of the electron beam e is provided between the filament 7 in the tube and the target T, the X-ray generation point (target T) and the sample S can be brought closer to each other. Further, since the shutter 11 is closed until the electron beam e, which is the thermoelectron from the filament 7, is stabilized, and the shutter 11 is opened after stabilization, measurement with the stable electron beam e is possible.
Further, since the analyzer 5 and the display unit 6 are integrally mounted on the vacuum housing 2, the analysis result can be confirmed on the spot by the analyzer 5 and the display unit 6, and the size is small. It can be a lightweight handy type.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, one X-ray detection element 4 having a transmission hole 4a formed in the center is used. As another example 1, as shown in FIG. An element in which the line detection element 14 is arranged may be used. As another example 2, only one X-ray detection element 14 may be disposed around the target T as shown in FIG.
The above embodiment is an energy dispersive X-ray fluorescence analyzer, but may be applied to other analysis methods, for example, a wavelength dispersive X-ray fluorescence analyzer.
In addition, as an X-ray tube described in Patent Document 1, a so-called reflection type that generates primary X-rays by irradiating a columnar target with an electron beam from an annular filament disposed around the target. It doesn't matter.

  Further, the present invention is suitable for a handy type X-ray analyzer as in the above embodiment, but may be applied to a stationary type X-ray analyzer. For example, the X-ray tube constituted by the vacuum casing 2, the electron beam source 3, the target T, and the X-ray detection element 4, and the analyzer 5, the control system, the display unit 6 and the like are provided separately. A stationary X-ray analyzer may be used.

In one Embodiment of the X-ray analyzer which concerns on this invention, it is a schematic whole block diagram which shows an X-ray analyzer. In this embodiment, it is a front view of the principal part which shows the positional relationship of a target and an X-ray detection element. In other example 1 of this embodiment, it is a front view of the principal part which shows the positional relationship of a target and an X-ray detection element. In other example 2 of this embodiment, it is a front view of the principal part which shows the positional relationship of a target and an X-ray detection element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Window part, 2 ... Vacuum housing, 3 ... Electron beam source, 4, 14 ... X-ray detection element, 4a ... Transmission hole, 5 ... Analyzer, 6 ... Display part, 10 ... Metal guard member, 11 ... Shutter , 13 ... shielding body, e ... electron beam, X1 ... primary X-ray, X2 ... fluorescent X-ray and scattered X-ray, S ... sample, T ... target

Claims (7)

A vacuum housing having a window portion formed of an X-ray transmission film that is in a vacuum state and capable of transmitting X-rays;
An electron beam source installed in the vacuum housing and emitting an electron beam;
A target installed near or in contact with the window in the vacuum housing so that the electron beam is irradiated to generate primary X-ray and the primary X-ray can be emitted to an external sample through the window. When,
The electron beam source is disposed around the target in the vacuum casing and in the vicinity of the window so as to detect fluorescent X-rays and scattered X-rays emitted from the sample and incident from the window. And an X-ray detection element that outputs a signal including energy information of the fluorescent X-rays and scattered X-rays in the region between the target and the target. Wire tube. The X-ray tube according to claim 1 ,
An X-ray tube, wherein the X-ray detection element is disposed in a region between the electron beam source and the target and has a transmission hole through which the electron beam can pass. The X-ray tube according to claim 1 or 2 ,
An X-ray tube, wherein at least one of the target and the window is set to a ground potential or a positive potential. In the X-ray tube as described in any one of Claim 1 to 3 ,
An X-ray tube characterized in that a shutter capable of moving back and forth in the path of the electron beam is provided between the electron beam source and the target. In the X-ray tube as described in any one of Claim 1 to 4 ,
An X-ray tube, wherein a shielding body for blocking radiant heat from the electron beam source is disposed between the electron beam source and the X-ray detection element. An X-ray tube according to any one of claims 1 to 5 ;
An analyzer for analyzing the signal;
An X-ray analysis apparatus comprising: a display unit that displays an analysis result of the analyzer. The X-ray analyzer according to claim 6 ,
An X-ray analyzer characterized in that the analyzer and the display unit are provided in the vacuum casing to be portable.

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