X-ray diffraction method and portable X-ray diffraction apparatus using same

A portable X-ray diffraction apparatus is provided which can be held by a person and on which an image of a spot to be measured can be viewed. The portable X-ray diffraction apparatus includes: X-ray irradiation means that irradiates a sample with collimated X-rays; diffracted X-ray detection means that detects a collimated portion of diffracted X-rays among X-rays diffracted from the sample by the irradiation of the X-rays with the X-ray irradiation means; and signal processing means that processes a signal outputted from the diffracted X-ray detection means. An X-ray diffraction method is used which includes: irradiating a sample with collimated continuous-wavelength X-rays; extracting a collimated portion of diffracted X-rays diffracted from the sample irradiated with the X-rays and condensing the extracted collimated portion of the diffracted X-rays; detecting, using an energy dispersive detection element, the condensed diffracted X-rays; and processing a signal detected by the detection element.

TECHNICAL FIELD

The present invention is related to an X-ray diffraction method for analyzing a material by irradiating a sample with continuous wavelength X-rays generated by an X-ray tube and a portable X-ray diffraction apparatus using the same.

BACKGROUND ART

Applications have been established for X-ray diffraction methods as methods for identifying an unknown crystalline sample or for measuring a part of a large sample or a sample mounted on a substrate varying in kind. Under the circumstances, request has been growing larger for measuring devices which can be used outdoor to perform functions of analyzing devices which used to be used indoors. Thanks to the progress of electronic technology in recent years, power supply units and control circuits have been made smaller, lighter, and less power consuming. General X-ray diffraction methods, however, pose a problem that, when a sample is shifted out of position, their measurement accuracy or sensitivity is degraded. Hence, X-ray diffraction measurements have been performed using a mechanical angle measuring device called a goniometer to keep a sample correctly positioned.

As for the existing methods, the non-patent literature 1, for example, describes a measuring device which uses a goniometer to movably keep a sample, an X-ray source, and a detector in position. The patent literature 1, on the other hand, discloses a portable X-ray diffraction apparatus aimed at measuring X-ray diffraction at a specific part of a sample.

Also, in the non-patent literature 2, an X-ray diffraction measurement method is described in which an X-ray detector capable of X-ray photon energy analysis is used and in which no X-ray angle measuring device is used.

CITATION LIST

Patent Literature

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

Generally, in X-ray diffraction measurement, X-ray diffraction intensities are measured at different X-ray diffraction angles using an X-ray detector, so that it has been necessary to perform measurement while changing the angles and positions of the sample and detector for every X-ray diffraction angle used. Therefore, the mechanical angle measuring device to be used is inevitably required to be heavy so as to keep an X-ray source and an X-ray detector securely in position and secure accuracy in changing their angles. It has, therefore, been difficult to use general X-ray diffraction apparatuses as portable apparatuses.

Energy analyzing type X-ray diffraction apparatuses which do not require angle changes use a large X-ray detector and, in such X-ray diffraction apparatuses, a sample and a detector are set apart so as to secure X-ray diffraction measurement accuracy. It has, therefore, been difficult to make energy analyzing type X-ray diffraction apparatuses with their weights and dimensions portable.

It has been difficult to make mechanical angle measuring devices like the one described in the non-patent literature 1 compact and light. As for the device described in the patent literature 1, it has been necessary to adopt a complicated configuration including a jig for attaching the device to a sample and plural two-dimensional detectors. Furthermore, according to the X-ray diffraction measurement method described in the non-patent literature 2 in which no X-ray angle measuring device is used, it is necessary to cool an X-ray detector to the temperature of liquid nitrogen, so that a large coolant container is required. In the method, it is also necessary to set a sample and the detector apart so as to secure measuring accuracy. Thus, the method is not necessarily applied to portable X-ray diffraction apparatuses.

The present invention has been made in view of the above problems with existing techniques, and it is an object of the present invention to realize a compact and light X-ray diffraction apparatus and provide an X-ray diffraction method and a portable X-ray diffraction apparatus using the method which enable data to be obtained with sufficiently stable accuracy even when the apparatus is used while being held by a person.

Solution to Problem

The present invention has been made, as described above, for realization of a compact and light portable X-ray diffraction apparatus which can be held by a person. Particularly, the invention has been made based on the following knowledge of the inventors. Namely, X-ray diffraction measurements used to be made under the conditions where the positional relationship among the incident X-rays, a sample, and the diffracted X-rays is securely maintained. For example, special X-rays (when a Cu target is used, wavelength of Kα is 0.15418 nm) are radiated from an X-ray tube to a sample, and diffracted X-rays from the sample are measured. This measurement is performed, based on Bragg rule, using a mechanical angle setting device called a goniometer so as to accurately maintain a relationship among an X-ray tube, a sample and an X-ray detector. A mechanical goniometer is heavy, so that it is not an appropriate device to be used for measurement while being held by a person. Hence, an X-ray diffraction method and an X-ray diffraction apparatus using the method which, requiring no goniometer, enable measurement without being affected by shifting of the sample position if caused while the apparatus is held by a person have been demanded.

To achieve the above object, a portable X-ray diffraction apparatus according to the present invention includes: X-ray irradiation means that irradiates a sample with collimated X-rays; diffracted X-ray detection means that detects a collimated portion of diffracted X-rays among X-rays diffracted from the sample by the irradiation of the X-rays with the X-ray irradiation means; and signal processing means that processes a signal outputted from the diffracted X-ray detection means.

To achieve the above object, an X-ray diffraction method according to the present invention includes: irradiating a sample with collimated continuous-wavelength X-rays; selecting a collimated portion of diffracted X-rays diffracted from the sample irradiated with the collimated continuous-wavelength X-rays and condensing the selected collimated portion of the diffracted X-rays; detecting, using an energy dispersive detection element, the condensed diffracted X-rays; and processing a signal detected by the detection element.

Furthermore, to achieve the above object, an X-ray diffraction method according to the present invention includes: imaging a spot on a sample to be irradiated with X-rays; displaying an image thus imaged of the spot on the sample to be irradiated with X-rays; generating continuous wavelength X-rays using an X-ray tube; collimating the X-rays generated by the X-ray tube and obliquely irradiating the spot on a sample to be irradiated with the collimated X-rays, an image thereof is displayed; selecting and condensing a collimated portion of X-rays diffracted from the sample irradiated with the X-rays; detecting the selected and condensed diffracted X-rays using a detection element; and processing a signal detected by the detection element.

Advantageous Effects of Invention

The present invention, while making it possible to realize an X-ray diffraction apparatus of a size and weight to allow the apparatus to be carried and held by a person, can provide an X-ray diffraction method and a portable X-ray measuring apparatus using the method which enable X-ray diffraction measurement to be performed while observing a microscopic image of a specific part of a large sample on a display and which also enable stable X-ray measurement on such a specific part even when the sample surface is uneven or the sample position tends to move.

DESCRIPTION OF EMBODIMENTS

FIG. 1is a diagram showing an overall configuration of a portable X-ray diffraction apparatus100according to an embodiment of the present invention. A housing cylinder21included in an X-ray irradiation section20is internally provided with an X-ray tube1for X-ray generation, an X-ray shutter2, an X-ray optical element3for sample irradiation, and an X-ray transmission window22. A housing cylinder31included in an X-ray detection section30is internally provided with an X-ray transmission window32, a diffracted X-ray receiving optical element4, and an X-ray detector5. Furthermore, a sample observation section6, a high-voltage power supply7for X-ray generation, a detector signal processing section8, a high-voltage power supply and shutter opening/closing control section9, a data processing and display control section10, an electricity accumulation section11, a power cable12, a handle13, a shutter opening/closing switch14, and a collapsible data display section15are installed in a housing section50.

The housing cylinder21included in the X-ray irradiation section20and the housing cylinder31included in the X-ray detection section30are mutually spatially connected and are both attached to the housing section50. Also, the insides of the housing cylinder21included in the X-ray irradiation section20and the housing cylinder31included in the X-ray detection section30are evacuated by evacuation means, not shown. Furthermore, a ring-shaped X-ray shielding section40is attached to the surfaces, which is facing a sample200, of the housing cylinder21included in the X-ray irradiation section20and housing cylinder31included in the X-ray detection section30so as to prevent the X-rays emitted from the X-ray irradiation section20to the sample200from looking outward. The contacting part41of the ring-shaped X-ray shielding section40comes in contact with the sample200to prevent the X-rays from leaking outward.

In the above configuration, on/off of the irradiation of the X-rays generated by the X-ray tube1to a sample is controlled by the shutter open/close switch14by operating the X-ray shutter2open/close. In a state where the shutter2controlled by the shutter open/close switch14is open, the X-rays generated by the X-ray tube1transmit through an X-ray optical element3and irradiate the sample200.

The X-ray optical element3collimates the X-rays generated by the X-ray tube1to irradiate the sample200with the collimated X-rays. The X-ray optical element3used in the present embodiment is a slit with an opening size similar to the size of an X-ray focus16of the X-ray tube1. The X-ray optical element3may be a parallel tube type monocapillary or it may be a polycapillary type element formed by bundling plural parallel tube type monocapillaries.

Part of the X-rays reflected (including scattered) from the sample irradiated with the X-rays enter a diffracted X-ray receiving optical element4and reach the X-ray detector5. The diffracted X-ray receiving optical element4is a polycapillary type element formed by bundling plural parallel tube type monocapillaries. Among the X-rays entered into the diffracted X-ray receiving optical element4, a collimated portion of the X-rays enters the polycapillary type diffracted X-ray receiving optical element4. The X-rays entered into the polycapillary type diffracted X-ray receiving optical element4are transmitted through the polycapillary type diffracted X-ray receiving optical element4and enter the X-ray detector5capable of X-ray energy measurement where the X-rays diffracted from the sample are measured. The polycapillary type diffracted X-ray receiving optical element4is formed such that the X-rays outputted therefrom are condensed on the detection surface (not shown) of the X-ray detector5.

An analog signal obtained by detecting X-rays at the X-ray detector5is digitized, for subsequent data processing, at the detector signal processing section8and is processed at the data processing and display control section10. The results of the processing are displayed on the collapsible data display section15. In the attached drawings, chain lines a and b each denotes an optical axis of an X-ray beam used for X-ray diffraction measurement in the portable X-ray diffraction apparatus100of the present embodiment.

In the present embodiment as shown inFIG. 1, an ideal position of the sample200relative to the optical axis a of an X-ray beam used for X-ray diffraction measurement is represented, inFIG. 2, by reference symbol S. In measurement performed using the portable X-ray diffraction apparatus100held by a person, keeping the sample200in an ideal position is difficult and the sample position is assumed to shift in a range denoted by L inFIG. 2. Namely, the position of the sample200to cause diffraction shifts between S1and S2(shifting width: L).

When it is assumed that nothing like the polycapillary type diffracted X-ray receiving optical element4shown inFIG. 1is provided on the X-ray detection section30and that the X-rays reflected from the sample200travel straight in a direction defined by angle θ2, shifting width D0of the optical axis b of the diffracted X-ray beam as measured on a cross-sectional surface of the diffracted X-ray receiving optical element4is given by the following equation (1).
D0=L×sin(θ1+θ2)/sin((θ1+θ2)/2)  (1)
where θ1is the incident angle of the X-rays to the sample from the X-ray optical element3and θ2is the output angle of the X-rays diffracted from the sample. Both θ1and θ2are set to be in the range of 10 to 60 degrees.

When the sample position is shifted by L with the incident X-ray beam having diameter d, the surface of the X-ray detector5is required, to allow stable measurement of diffracted X-rays, to be larger than D1given by the following equation (2).
D1=d+D=d+L×sin(θ1+θ2)/sin((θ1+θ2)/2)   (2)

Next, the theory of the X-ray detection section30for collecting diffracted X-rays to be entered into the diffracted X-ray receiving optical element4shown inFIG. 1will be partly described with reference toFIG. 3. The diffracted X-ray receiving optical element4used in the present embodiment is a polycapillary formed by bundling parallel tube type monocapillaries and has a parallel portion. A polycapillary changes the shape of an X-ray beam by making use of the total reflection of X-rays on the smooth inner surfaces of glass capillary tubes. The critical angle for X-ray total reflection at silica glass depends on the wavelength (energy) of the X-rays. When the X-ray wavelength is 0.083 nm and energy is 15 keV, the critical angle is about 0.125° (2.2 mrad).

Referring toFIG. 3, when the polycapillary4is formed of bundled monocapillaries each with a glass tube inner diameter of 200 nm, an X-ray beam entering the polycapillary4at a total-reflection critical angle is totally reflected about once every 100 μm. Namely, it is totally reflected 100 times in the parallel polycapillary4with a length T1of 10 mm. When, in this case, the reflectivity of total reflection is 0.99, most of the X-rays entering the polycapillary4from the incident end401thereof at an angle of 0.125° are absorbed inside the polycapillary. When an X-ray beam enters the polycapillary4at about 0.06°, i.e. about half the total-reflection critical angle, the number of times of total reflection in the parallel polycapillary4is halved to 50 resulting in an output intensity of about 50% for the X-ray beam outputted from the polycapillary. Thus, the relationship between the incident angle of X-ray beam and the intensity of X-ray beam output from the polycapillary is as shown inFIGS. 4A and 4B.

An X-ray beam with a wavelength shorter than 0.083 nm (with an energy higher than 15 keV) cannot pass through the parallel polycapillary unless it is entered with a still smaller incident angle. Because an X-ray beam with a long wavelength (with a low energy) is reflected at about the same reflectivity as an X-ray beam with a short wavelength, an X-ray beam with a long wavelength cannot pass through the parallel polycapillary, either, if it is entered into the polycapillary at a large incident angle to result in an increased number of times of total reflection. Hence, it is possible using the polycapillary4formed by bundling 10 mm long monocapillaries each with a glass tube inner diameter of 200 nm to select only a collimated X-ray beam with an angular divergence of about 0.12°.

The collimation operation performed, as described above, by the polycapillary4can also be performed using an ordinary multi-layered collimator. It is possible to use a compact multi-layered collimator.

An output end402of the polycapillary4is, as being described later, arranged such that the X-rays outputted from the output end402of the polycapillary4are condensed on the detection surface of the X-ray detector5so as to allow the detection surface to be smaller than D1. The X-ray detector5can, therefore, be made smaller than in the configuration described with reference toFIG. 2.

Next, referring toFIG. 3, design of the parallel capillary type, diffracted X-ray receiving optical element4used in the present embodiment of the present invention will be described. The opening diameter D1on the incident end401of the X-ray receiving optical element4is given by the foregoing equation (2). When an X-ray beam has a diameter (d) of 1 mm, as a practical value, and the sample position shifting range (L) is also practically ±2 mm, the incident end401of the light receiving optical system is required to have an opening diameter (D1) of about 9 mm. For use in place of the X-ray detector5, silicon drift type semiconductor detectors (SSD) with a diameter of 10 mm have been commercially available as energy dispersive X-ray detectors. One of such SDDs may be directly attached, as the X-ray detector5, to one end of the parallel polycapillary.

In the present embodiment, a light receiving optical element which, making use of a characteristic of a polycapillary, allows the X-ray detector5to have a reduced diameter is used. When the X-ray wavelength is 0.083 nm and energy is 15 keV as cited above, the total-reflection critical angle at a silica surface is 0.125° (2.2 mrad), so that the reflection angle can be set about 0.25° for one total reflection. By reducing the diameter of the polycapillary gradually and smoothly from the X-ray receiving part (X-ray incident side) thereof forming the polycapillary into a rotary ellipsoidal surface shape, the diameter of the diffracted X-ray beam can be reduced through total reflection at inner walls of the polycapillary. When the diffracted X-ray beam diameter is reduced by about 5° on a linear average basis through 20 times of total reflection, the opening diameter at the output end402, spaced from the parallel polycapillary portion by T2=24 mm, of the polycapillary is about 6 mm. Thus, the diffracted X-ray beam entered through the incident end401with a diameter of 10 mm can be condensed and outputted from the output end402. When, in this case, the reflectance of total reflection is assumed to be 0.99, the reduction in X-ray intensity is only about 20%.

Using a reduction optical element as described above makes it possible to use a detector with a diameter of 6 mm (with an area of 25 mm2) (calculated values) instead of the X-ray detector5with a diameter of 10 mm (with an area of 80 mm2). Currently, large silicon drift detectors are expensive while compact detectors are superior in terms of energy resolution characteristics, so that using a compact optical element is advantageous. Furthermore, when the polycapillary portion, formed to have a cross sectional shape like a rotary ellipsoidal surface, on the output end402is made 50 mm long (T2=50 mm), the opening diameter required on the output end402is about 2 mm, so that one of inexpensive mass-produced detectors with an area of 7 mm2(with a diameter of 3 mm) can be used.

The calculated values presented above are based on a total-reflection critical angle. The polycapillary used in the present embodiment of the present invention has a smooth rotary ellipsoidal surface shape and measures 50 mm in length and 10 mm in opening diameter at the incident end401which is reduced to measure 5 mm at the output end402. What is required to this polycapillary is to condense the incident X-rays and output the condensed X-rays toward the X-ray detector5. Namely, the polycapillary is not required to have a focusing function, so that it can be formed to have a smooth two-dimensionally curved surface.

Next, with reference toFIG. 5, the X-ray tube1for X-ray generation, the high-voltage power supply7for X-ray generation and the high-voltage power supply and shutter open/close control section9used in the present embodiment of the present invention will be described. The X-ray tube1for X-ray generation is a compact X-ray tube using a ceramic insulator. It may also be a glass tube type X-ray tube. When, in cases where the overall circuit configuration is of an anode (a target) ground type, a hot cathode is used, a filament transformer of a high voltage insulation type is required. When the overall circuit configuration is of a cathode ground type, such a high voltage insulation type filament transformer is not required and having an advantage in reducing weight. Hence, in the present embodiment, the overall circuit configuration is of a cathode ground type. InFIG. 5, 17is a cathode (target) and18is an anode including a filament18aand electrode18b. In the present embodiment, the heat (10 W) generated in the X-ray tube1is released by heat conduction via a high voltage insulator in the X-ray measurement apparatus.

The high voltage power supply7for X-ray generation includes a high-voltage boost rectifier circuit70which is a 12-stage Cockcroft-Walton circuit for full-wave rectification. For high-frequency power supply to the Cockcroft-Walton high-voltage boost rectifier circuit70, a piezoelectric transformer71is used. A power of 4 kV-10 W is supplied by the single piezoelectric transformer71with an operating frequency of about 80 kHz. The piezoelectric transformer71is supplied with ±24 V at high frequency by the high-voltage power supply and shutter open/close control section9. The high-voltage power supply and shutter open/close control section9is controlled by the data processing and display control section10so as to maintain a voltage set from outside. This control is performed using negative feedback based on an 80 kHz of high-frequency output circuit91and the voltage applied to the X-ray tube1for X-ray generation.

The high-voltage power supply and shutter open/close control section9includes a filament current control section92to control the current of the X-ray tube1and a switch circuit93for the X-ray shutter2. The X-ray tube1and the high-voltage power supply7are integrally molded in a high-voltage power supply safety shield77as shown inFIG. 6B. To secure safety in manufacture and operation as well as in adjustment and inspection work, no voltage exceeding 24 V is applied to the external terminals of the high-voltage power supply safety shield77.

In the present embodiment, the piezoelectric transformer71is adopted for its compactness and lightness, but a high-frequency coil transformer may also be used even though the transformer weight may somewhat increase.

Next, with reference toFIGS. 6A and 6B, the structure of the high-voltage power supply7for X-ray generation will be described. The high-voltage power supply7is formed, on a ceramic substrate75on which chip capacitors73, chip diodes74and chip resisters (not shown inFIG. 6) are mounted. These chip components are ones designed for surface mounting so as to make the device compact. With the voltage of each stage of the Cockcroft-Walton high-voltage boost rectifier circuit70set to 4 kV, bridge circuits72each include a chip capacitor73with a withstanding voltage of 4 kV and two series-connected chip diodes74each with a withstanding voltage of 2 kV and make up a 12-stage full-wave rectifying circuit. Hence, in the present embodiment of the present invention, the rated working voltage and current are set to 40 kV and 0.25 mA, respectively, for a maximum applied voltage of 48 kV. A higher voltage can be made available by increasing the number of stages of the full-wave Cockcroft-Walton rectifying circuit.

The high-voltage power supply7for X-ray generation includes a chip resistor (not shown) for voltage division for voltage negative-feedback control and a piezoelectric transformer71mounted on the back side of the ceramic substrate75. The piezoelectric transformer71being shaped like a thin rectangular shape is optimum for compact mounting. As compared with an electromagnetic high-frequency transformer, the piezoelectric transformer is, when considered for use in a compact device, superior in terms of electromagnetic noise. Because the piezoelectric transformer, by its principle, vibrates at high frequency (80 kHz), it is put in a case77of Teflon (registered trademark) for mounting on the substrate.

Next, with reference toFIGS. 7A and 7B, X-ray diffraction measurement performed according to the present embodiment will be described in detail. As shown inFIG. 7A, an X-ray beam generated at an X-ray focus16of the X-ray tube1for X-ray generation passes the X-ray optical element3for sample irradiation and is emitted to the sample200through the sample irradiating X-ray transmission window22provided on the sample side of the X-ray shielding section40shown inFIG. 7B. The contacting part41to be in contact with the sample200is made of heavy metal such as tungsten (W), tantalum (Ta) or lead (Pb) and is designed to prevent, when put in tight contact with the sample, the X-rays from leaking. Furthermore, to enhance safety during operation, plastic pieces (not shown) containing heavy metal are externally disposed to fit the shape of the sample as added means of X-ray leakage prevention. As a further safety arrangement, before X-ray emission is controlled by turning the shutter open/close switch14on/off, whether the contacting part41of the X-ray shielding section40is in contact with the sample is determined based on data obtained from a proximity switch (not shown) and the sample observation section6which performs optical measurement through a sample observation opening42.

A part of the X-ray beam emitted to the sample200is diffracted by the sample200and enters, as a diffracted X-ray beam, the diffracted X-ray receiving optical element4via the diffracted X-ray detection and transmission window32and is led to the X-ray detector5for measuring X-ray diffraction data. In the case of the present embodiment, a molybdenum target is used in the X-ray tube1for X-ray generation and the sample irradiating X-ray angle (θ1) and the diffracted X-ray collection angle (θ2) are both set to 20°, making value d, which is crystal lattice spacing, measurable in the range of 0.7 nm to 0.07 nm. The X-ray wavelength range of 0.5 nm to 0.07 nm is used for the measurement. Since X-rays with a wavelength of 0.3 nm or longer, for example, X-rays with a wavelength of 0.5 nm (2.4 keV), are easily absorbed in the atmosphere, the insides of the housing cylinder21included in the X-ray irradiation section20and housing cylinder31included in the X-ray detection section30have been evacuated by unillustrated means. Even though, in the present embodiment, the housing cylinders have a completely vacuum-sealed structure, housing cylinders which are not kept vacuum-sealed and are exhausted using a pump only when using the apparatus may be used.

In the present embodiment, the housing cylinders21and31included in the X-ray irradiation section20and X-ray detection section30, respectively, and the contacting part41of the X-ray shielding section40are mutually relatively rotatable and also the housing cylinders21and31included in the X-ray irradiation section20and X-ray detection section30, respectively, and the housing section50are mutually relatively rotatable. This makes it possible to manually turn the housing section50and display, while the sample is being measured, measured data in the collapsible data display section15. Continuing measurement while turning such sections makes it possible to collect averaged data, so that accurate and stable measurement is enabled. Furthermore, a direction in which a specific diffraction pattern appears can be determined, so that the orientation of crystals to cause X-ray diffraction from the sample can be determined.

An example of a detection signal outputted from the X-ray detector5having detected a diffracted X-ray beam is shown inFIG. 8. In the present embodiment, the X-ray detector5is an energy dispersive SDD. The SDD is a single pixel sensor. Therefore, making an X-ray beam diffracted from the sample200in a direction of diffraction angle θ2enter the incident end401of the polycapillary4having a large diameter and detecting the diffracted X-ray beam after condensing it approximately to the pixel size of the X-ray detector5is effective in enhancing the detection sensitivity of the X-ray detector.

When a detection signal as shown inFIG. 8is received, the detection signal processing section8calculates, by processing the signal, the crystal lattice spacing d of the sample200.

The relationship between crystal lattice spacing d of the sample200and peak wavelength λ is, based on Bragg's condition, expressed as follows.
2dsin θ=λ  (3)

where θ is an X-ray incident angle.

The relationship between wavelength λ (nm) and energy E (keV) is expressed as follows.
λ=1.24/E(4)

When equation (4) is substituted into equation (3) with X-ray incident angle θ set to 30°, crystal lattice spacing d can be expressed as follows.
d=1.24/E(5)

Thus, crystal lattice spacing d can be determined based on a detection signal of photon energy as shown inFIG. 8and equation (5).

Using the data obtained about crystal lattice spacing d and based on the relationship between internal stress and crystal lattice spacing d, the internal stress of the sample200can be determined.

When an anode target of molybdenum (Mo) is used in the X-ray tube1, X-rays with an energy in the range of 3 to 15 keV can be detected, so that, based on equation (5), crystal lattice spacing d of the sample200can be detected in the range of 0.41 to 0.083 nm.

When an anode target of silver (Ag) is used in the X-ray tube1, X-rays with an energy in the range of 3 to 20 keV can be detected, so that, based on equation (5), crystal lattice spacing d of the sample200can be detected in the range of 0.41 to 0.062 nm.

According to the present embodiment, it is possible to extract, using a polycapillary type optical element, only a collimated portion of the diffracted X-rays entered, after being diffracted from a sample irradiated with X-rays, in the housing cylinder31included in the X-ray detection section30, so that, even when the sample surface is varied in height, a collimated portion of the diffracted X-rays can be securely detected. This makes it easy to attach a portable X-ray diffraction apparatus to a sample. Thus, a sample can be analyzed efficiently using a portable X-ray diffraction apparatus.

Since variations in the height of a sample surface are tolerated to a certain extent, even a rough-surfaced sample or a sample with a flexible wavy surface can be analyzed.

Also, since a polycapillary type optical element is used to condense diffracted X-rays to be detected, the X-ray detector to be used can be made compact. This allows the portable X-ray diffraction apparatus to be made more smaller and lighter.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a portable X-ray diffraction apparatus for analyzing a sample by an X-ray diffraction method in which continuous wavelength X-rays generated by an X-ray tube are emitted to the sample.

REFERENCE SIGNS LIST