CN110987990B - High-energy monochromatic flash X-ray diffraction imaging method and system - Google Patents
High-energy monochromatic flash X-ray diffraction imaging method and system Download PDFInfo
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Abstract
The invention discloses a high-energy monochromatic flash X-ray diffraction imaging system, which comprises an emission collimation module, a monochromatic separation module and a diffraction imaging module, wherein the emission collimation module comprises a flash X-ray machine and a collimation unit, the flash X-ray machine emits X-rays, and the collimation unit is connected with the flash X-ray machine and is positioned on the line of an X-ray emission end; the single-color separation module is arranged along the X-ray and comprises a single-color unit and an emergent unit, wherein the single-color unit is connected with the emergent unit, and the emergent unit is positioned at one side of the emergent end of the single-color unit; the diffraction imaging module is positioned along the emergent direction of the single-color separation module and comprises an imaging plate and a rotating seat, and the rotating seat is arranged at the bottom end of the imaging plate; the method solves the problem of difficult monochromatic separation of the flash X-ray, and simultaneously the determined accurate diffraction angle can improve the signal to noise ratio of the diffraction image, thereby greatly reducing the complexity of the system.
Description
Technical Field
The invention relates to the technical field of X-ray monochromatic separation, in particular to a high-energy monochromatic flash X-ray diffraction imaging method and system.
Background
Both X-ray and transmission electron microscopy can study defects inside the crystal. Although the transmission electron microscope has extremely high resolution, the preparation process of the sample is complex, the sample needs to be destroyed, and only small parts in the sample can be observed at a time. Even if in situ tensile experiments can be performed, the sample thickness needs to be thinned to the micrometer scale. However, the in-situ plastic deformation research by the X-ray method can be carried out without damaging the crystal, the whole observation of the sample can be carried out, the sample preparation is easy, and the dislocation type can be determined and the dislocation density can be estimated.
X-ray diffraction experiments to study in-situ stretching or compression mostly need to be performed on synchrotron radiation devices. Because of the huge volume of the synchrotron radiation light source, the whole technology of the system has high complexity and very high cost, and the place with the synchrotron radiation light source is few, the experiment has a plurality of limitations. Therefore, the development of related industries is limited, and therefore, a high-energy monochromatic flash X-ray diffraction imaging method and system are provided, so that an X-ray diffraction experiment is miniaturized and simplified.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description summary and in the title of the application, to avoid obscuring the purpose of this section, the description summary and the title of the invention, which should not be used to limit the scope of the invention.
The invention is provided in view of the problems of incomplete monochromism and low intensity of the existing flash X-ray.
Therefore, the technical problem to be solved by the invention is to provide a high-energy monochromatic flash X-ray diffraction imaging method and system, and the purpose is to generate flash X-rays with short wavelength, high intensity and good monochromaticity, which can be used for in-situ dislocation evolution analysis of crystals.
In order to solve the technical problems, the invention provides the following technical scheme: the system comprises an emission collimation module, a monochromatic separation module and a diffraction imaging module, wherein the emission collimation module comprises a flash X-ray machine and a collimation unit, the flash X-ray machine emits X-rays, and the collimation unit is connected with the flash X-ray machine and is positioned on the line of an X-ray emission end; the single-color separation module is arranged along the X-ray and comprises a single-color unit and an emergent unit, wherein the single-color unit is connected with the emergent unit, and the emergent unit is positioned at one side of the emergent end of the single-color unit; the diffraction imaging module is positioned along the emergent direction of the single-color separation module and comprises an imaging plate and a rotating seat, and the rotating seat is arranged at the bottom end of the imaging plate.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: the flash X-ray machine comprises a high-voltage pulse generator and a flash X-ray tube, wherein X-rays emitted by the flash X-ray tube comprise K alpha rays, K alpha rays and K beta rays.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: the collimating unit comprises a lead collimator, a brass tube collimator and a glass capillary tube, wherein the brass tube collimator is connected to the outlet end of the lead collimator, and the glass capillary tube is arranged in the inner cavity of the lead collimator and is communicated with the inlet end and the outlet end of the glass capillary tube.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: the single-color unit comprises a brass cylinder, a single crystal and an angular platform, wherein the single crystal is positioned in the inner cavity of the brass cylinder and is placed at the top of the angular platform, and the bottom of the angular platform extends outside the brass cylinder through the side wall of the brass cylinder.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: the angle position platform comprises a pitching platform, a rotating platform and a fine tuning rod, wherein the pitching platform is fixed at the top of the rotating platform, and the fine tuning rod is connected to the rotating shaft line of the rotating platform.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: the emergent unit comprises an emergent brass tube, a transverse moving plate and a longitudinal moving plate, wherein the transverse moving plate and the longitudinal moving plate are respectively movably matched with the two ends of the emergent brass tube, and one end of the emergent brass tube matched with the transverse moving plate is connected with the emergent end of the brass cylinder.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: a limiting rod and a connecting groove are arranged at one end of the emergent brass tube matched with the transverse moving plate, and a U-shaped chute is arranged at one end of the emergent brass tube matched with the longitudinal moving plate; a longitudinal slit is formed in the middle of the side wall of the transverse moving plate; and the middle part of the side wall of the longitudinal moving plate is provided with a transverse slit.
The invention aims to provide a high-energy monochromatic flash X-ray diffraction imaging method, which aims to generate flash X-rays with short wavelength, high intensity and good monochromaticity, which can be used for in-situ dislocation evolution analysis of crystals by operating the system.
In order to solve the technical problems, the invention provides the following technical scheme: the high-energy monochromatic flash X-ray diffraction imaging method adopts the diffraction imaging system and further comprises the following steps:
determining appropriate experimental parameters, including selecting the monocrystal and the anode material of the flash X-ray tube;
calculating the length of the collimation unit according to the selected material, and respectively calculating diffraction angles of the K alpha rays and the difference value of the diffraction angles of the K alpha rays and the K alpha rays;
constructing a diffraction imaging model of the monochromatic flash X-ray according to the calculated value; starting the model, and determining that the single crystal is at an optimal diffraction position through adjustment;
the rotating base is adjusted so that the X-rays obtain the best diffraction imaging effect on the imaging plate after monochromatic separation.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: and respectively calculating the lengths of the lead collimator and the brass tube collimator according to the calculated lengths of the collimation units, wherein the outer diameter of the brass tube collimator is far smaller than the outer diameter of the lead collimator, and the inner diameters of the lead collimator and the brass tube collimator are the same.
As a preferable scheme of the high-energy monochromatic flash X-ray diffraction imaging method and system, the invention comprises the following steps: in the adjusting process, firstly, coarse adjusting the pitching table to enable the single crystal to be vertical to the horizontal plane; and driving the rotary table by fine tuning the fine tuning rod, and determining that the single crystal is at an optimal diffraction position by matching with the imaging plate.
The invention has the beneficial effects that:
the invention uses the flash X-ray machine to generate X-rays, the intensity and the incidence width of the rays are kept by the collimation unit, and then the unwanted rays are removed by the monochromatic unit, so that the flash X-rays with short wavelength, high intensity and good monochromaticity which can be used for in-situ dislocation evolution analysis of crystals are obtained, and the invention has wide practicability and extremely high economical efficiency; the method solves the problem of difficult monochromatic separation of the flash X-ray, and simultaneously the determined accurate diffraction angle can improve the signal to noise ratio of the diffraction image, thereby greatly reducing the complexity of the system.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is a schematic diagram of the overall structure of the high-energy monochromatic flash X-ray diffraction imaging method and system of the present invention.
Fig. 2 is a schematic structural diagram of the high-energy monochromatic flash X-ray diffraction imaging system of the present invention.
Fig. 3 is a schematic view of the lead slit position of the high-energy monochromatic flash X-ray diffraction imaging system of the present invention.
FIG. 4 is a schematic diagram of single crystal diffraction light paths in a single unit of the high energy monochromatic flash X-ray diffraction imaging method and system of the present invention.
FIG. 5 is a schematic diagram of the structure of an exit unit of the high-energy monochromatic flash X-ray diffraction imaging method and system of the present invention.
FIG. 6 is a schematic diagram of a partial explosion structure of an exit unit of the high-energy monochromatic flash X-ray diffraction imaging method and system of the present invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Further, in describing the embodiments of the present invention in detail, the cross-sectional view of the device structure is not partially enlarged to a general scale for convenience of description, and the schematic is only an example, which should not limit the scope of protection of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Example 1
Referring to fig. 1, a high-energy monochromatic flash X-ray diffraction imaging method and system are provided for a first embodiment of the present invention, the system includes an emission collimation module 100, a monochromatic separation module 200 and a diffraction imaging module 300, wherein the emission collimation module 100 includes a flash X-ray machine 101 and a collimation unit 102, the flash X-ray machine 101 emits X-rays, and the collimation unit 102 is connected with the flash X-ray machine 101 and is located on a line at an X-ray exit end; the single-color separation module 200 is arranged along the X-ray and comprises a single-color unit 201 and an emergent unit 202, wherein the single-color unit 201 is connected with the emergent unit 202, and the emergent unit 202 is positioned at one side of the emergent end of the single-color unit 201; the diffraction imaging module 300 is located along the outgoing direction of the single-color separation module 200, and comprises an imaging plate 301 and a rotating seat 302, wherein the rotating seat 302 is arranged at the bottom end of the imaging plate 301.
Wherein the flash X-ray machine 101 in the emission collimation module 100 has strong portability, and the generated X-ray has a certain intensity, the photon energy of the X-ray is between 10keV and 2MeV, the flash X-ray machine 101 is used for generating and emitting the X-ray, the collimation unit 102 collimates the generated X-ray, the intensity and the emission width of the X-ray are maintained, the X-ray emitted from the collimation unit 102 enters the monochromatic unit 201 in the monochromatic separation module 200, the X-ray which does not meet the bragg condition is removed in the monochromatic unit 201, the monochromatic X-ray which meets the condition is separated and emitted, the emitted monochromatic X-ray enters the emission unit 202, and the emission unit 202 can limit the divergence of the monochromatic X-ray emitted from the monochromatic unit 201 and control the emission direction of the monochromatic X-ray, the monochromatic X-ray emitted from the emission unit 202 enters the sample to be measured at a specific angle, and the diffracted beam thereof is finally imaged on the imaging plate 301 in the diffraction imaging module 300. The evolution process of dislocation in the deformation process of the sample to be detected can be analyzed by observing the change of diffraction spots on the imaging plate.
Example 2
Referring to fig. 1 and 2, a second embodiment of the present invention is different from the first embodiment in that: the flash X-ray machine 101 comprises a high voltage pulse generator and a flash X-ray tube, and X-rays emitted by the flash X-ray tube comprise kα1 rays, kα2 rays and kβ rays.
Compared with the embodiment 1, further, the high-voltage pulse generator in the flash X-ray machine 101 is matched with the console, so that the flash X-ray tube can emit high-energy flash X-rays, and the exposure time reaches nanosecond level; preferably, the anode material of the flash X-ray tube is a molybdenum (Mo) target for emitting short X-ray pulses with high energy and high brightness.
It should be noted that, the X-rays emitted by the flash X-ray diode include continuous X-rays and characteristic X-rays, wherein the characteristic X-rays further include kα1 rays, kα2 rays, and kβ rays, and the incident flash X-rays required for the in-situ stretch diffraction test in practice are strictly monochromatic kα1 rays, so that the monochromatic unit 201 realizes that only collimated monochromatic kα1 rays remain to be emitted from the emission unit 202, and kα2 rays and kβ rays are absorbed by the single crystal 201b in the monochromatic unit 201 because the bragg condition is not satisfied; the continuous X-rays are absorbed as they pass through the lead collimator 102 a.
The rest of the structure is the same as that of embodiment 1.
Example 3
Referring to fig. 1, 2 and 3, a third embodiment of the present invention is different from the second embodiment in that: the collimating unit 102 comprises a lead collimator 102a, a brass tube collimator 102b and a glass capillary tube 102c, wherein the brass tube collimator 102b is connected to the outlet end of the lead collimator 102a, and the glass capillary tube 102c is arranged in the inner cavity of the lead collimator 102a and is communicated with the inlet end and the outlet end of the glass capillary tube.
Compared with embodiment 2, further, the collimating unit 102 selects the lead collimator 102a and the brass tube collimator 102b for dual collimation, the lead collimator 102a is connected with the brass tube collimator 102b, and the two are internally provided with light channels for X-ray emission and are mutually communicated; the lead collimator 102a is also used to absorb continuous X-rays; meanwhile, in order to limit the incident width of the X-rays incident into the single crystal 201b in the monochromator unit 201, a lead slit having a width of 0.3mm was attached to the junction of the flash X-ray diode and the lead collimator 102 a.
The glass capillary 102c is an optical device manufactured according to the principle of total reflection, and the angle between the incident angle of the X-ray and the optical channel of the glass capillary 102c needs to satisfy the condition of total reflection. The glass capillary 102c is arranged in the lead collimator 102a, the glass capillary 102c is used as a waveguide tube of X-rays by utilizing the principle of total reflection with an incident angle smaller than a critical angle, the propagation direction of the light beam is changed, the X-rays are adjusted to be parallel or the high-brightness light beam with a certain shape and size is used as an X-ray source, the addition of the glass capillary 102c can ensure that the flash X-rays with certain attenuation have enough intensity after exiting from the monochromatic unit 201, obvious diffraction spots can be formed on an imaging plate, the energy loss of the flash X-rays can be reduced, the collimation of the flash X-rays is effectively improved, and the X-ray utilization rate is effectively improved.
Further, since the X-ray attenuates after being emitted, and the longer the length of the brass tube collimator 102b, the better the monochromatic separation effect of the X-ray, but the intensity of the X-ray also decreases, the most suitable length ratio of the lead collimator 102a and the brass tube collimator 102b needs to be calculated to ensure that the X-ray emitted from the collimating unit 102 has sufficient intensity and collimation.
The rest of the structure is the same as that of embodiment 2.
Example 4
Referring to fig. 1 and 2, a fourth embodiment of the present invention is different from the third embodiment in that: the mono-color unit 201 comprises a brass cylinder 201a, a single crystal 201b and a angular stage 201c, the single crystal 201b being located in the inner cavity of the brass cylinder 201a and being placed on top of the angular stage 201c, the bottom of the angular stage 201c extending through the side wall of the brass cylinder 201a on its outside.
The angular stage 201c includes a pitching stage 201c-1, a rotating stage 201c-2, and a fine adjustment lever 201c-3, the pitching stage 201c-1 being fixed to the top of the rotating stage 201c-2, the fine adjustment lever 201c-3 being connected to the rotation axis of the rotating stage 201 c-2.
Further, in comparison with embodiment 3, a single-color unit 201 is installed at the outlet of brass tube collimator 102b, wherein brass cylinder 201a is provided with an upper cover plate and a lower cover plate of brass for integrally sealing single crystal 201b; preferably, germanium (Ge) single crystals are selected as single crystals 201b in the X-ray monochromatic separation system, the single crystals 201b are placed on a single crystal fixing frame, a pitching table connecting plate is hinged to the top of a pitching table 201c-1, the single crystal fixing frame is arranged on the top of the pitching table connecting plate, a fine tuning rod 201c-3 is connected with a rotating table 201c-2, the fine tuning rod comprises a fine tuning bolt frame and a digital display, the pitching table 201c-1 is used for adjusting the vertical angle of the single crystals 201b, the rotating table 201c-2 is used for adjusting the included angle of X-rays and the single crystals 201b, and preferably, since the Bragg angle difference between K alpha 1 rays and K alpha 2 rays is small, the single crystals are difficult to read on the rotating table 201c-2 by naked eyes, the moving displacement of the fine tuning rod 201c-3 is more obvious by lengthening the length of the fine tuning rod 201c-3, and the moving displacement of the fine tuning rod 201c-3 is directly read in a matching with digital display (three positions after the fine tuning rod is accurate to decimal point) so as to obtain an angle value.
The rest of the structure is the same as that of embodiment 3.
Example 5
Referring to fig. 1, 2, 5 and 6, a fifth embodiment of the present invention is different from the fourth embodiment in that: the outgoing unit 202 includes an outgoing brass tube 202a, a lateral moving plate 202b and a longitudinal moving plate 202c, the lateral moving plate 202b and the longitudinal moving plate 202c are respectively movably fitted at two ends of the outgoing brass tube 202a, and one end of the outgoing brass tube 202a fitted with the lateral moving plate 202b is connected to an outgoing end of the brass cylinder 201 a.
A limiting rod and a connecting groove are arranged at one end of the emergent brass tube 202a matched with the transverse moving plate 202b, and a U-shaped chute is arranged at one end of the emergent brass tube matched with the longitudinal moving plate 202 c;
the middle part of the side wall of the transverse moving plate 202b is provided with a longitudinal slit 202b-1;
the middle of the side wall of the longitudinal moving plate 202c is provided with a transverse slit 202c-1.
Further, the emission unit 202 is for limiting the emittance of the X-rays emitted from the monochromatic unit 201 and controlling the emission direction of the monochromatic X-rays, as compared with embodiment 4; wherein, the outgoing brass tube 202a is fixed with the side wall of the brass cylinder 201a, and the angle formed by the outgoing brass tube 202b and the Ge monocrystal is just equal to the diffraction angle of the K alpha 1 ray, the inner cavity of the outgoing brass tube 202b is provided with an optical channel, the transverse moving plate 202b and the longitudinal moving plate 202c are movably matched at two ends of the outgoing brass tube 202a, and the longitudinal slit 202b-1, the transverse slit 202c-1 are communicated with the optical channel in the outgoing brass tube 202b in a matched manner, thereby limiting the outgoing direction of the monochromatic X rays.
The structure of the outgoing brass tube 202a, the lateral moving plate 202b and the longitudinal moving plate 202c is shown in the drawing, the lateral moving plate 202b is in a U shape, and is clamped in a connecting groove at the end of the outgoing brass tube 202a, and the lateral moving plate 202b is limited and slides by matching a limiting rod; the longitudinal moving plate 202c is shaped like a Chinese character 'zhong', and limit screws are symmetrically arranged at two ends of the rectangular plate, and the longitudinal moving plate longitudinally slides in the U-shaped chute and is limited and adjusted through fine adjustment screws at two ends of the longitudinal moving plate.
The rest of the structure is the same as that of embodiment 4.
Example 6
With reference to fig. 1 to 6, a sixth embodiment of the present invention provides a high-energy monochromatic flash X-ray diffraction imaging method, where the imaging method adopts the above diffraction imaging system, and further includes the following steps:
determining appropriate experimental parameters including selecting single crystal 201b and flash X-ray tube anode materials;
calculating the length of the collimation unit 102 according to the selected material, and respectively calculating diffraction angles of the K alpha 1 ray and the K alpha 2 ray and the difference value of the diffraction angles of the K alpha 1 ray and the K alpha 2 ray;
adjusting the imaging plate rotation base 302 so that the imaging plate 301 is always perpendicular to the horizontal plane and its direction is perpendicular to the direction of the monochromatic X-rays emitted from the transverse slit 202 c-1;
constructing a diffraction imaging model of the monochromatic flash X-ray according to the calculated value; by adjusting the angle table 201, the model is started, and the position with the maximum brightness of the imaging plate 301, namely the maximum number of received X-ray photons, is recorded, wherein the position is the diffraction position of the crystal 201b;
the monochromatic X-ray incident into the sample to be measured and emitted from the transverse slit 202c-1 can diffract a specific crystal plane of the sample to be measured, the direction of the diffracted beam is calculated according to the known crystal plane direction of the sample to be measured, and the imaging plate rotating base 302 is adjusted so that the imaging plate 301 is always perpendicular to the horizontal plane and perpendicular to the direction of the diffracted beam.
According to the calculated lengths of the collimation units 102, the lengths of the lead collimator 102a and the brass tube collimator 102b are respectively calculated, and the outer diameter of the brass tube collimator 102b is far smaller than the outer diameter of the lead collimator 102a, and the inner diameters of the lead collimator 102a and the brass tube collimator 102b are the same and communicated.
During the adjustment process, pitching stage 201c-1 is first coarsely adjusted so that single crystal 201b is kept vertical to the horizontal plane; and then the fine adjustment rod 201c-3 is shifted to drive the rotary table 201c-2, and the imaging plate 301 is matched to determine that the monocrystal 201b is in the optimal diffraction position.
Wherein, monocrystal 201b adopted in the imaging system is Ge monocrystal, and adopted anode material of the X-ray diode is Mo target; based on the materials selected, the most appropriate length ratios for both lead collimator 102a and brass collimator 102b are calculated, as well as the diffraction angles for the K.alpha.1 and K.alpha.2 rays and the differences in the diffraction angles for both.
Determination of appropriate experimental parameters
Determination of the diffraction angle θ of each of the Mo-K.alpha.1 rays and the Mo-K.alpha.2 rays 1 、θ 2 The difference θ between the diffraction angles of the two, the rotation diameter of the turntable 201c-2 and the length of the trimming rod 201c-3 converts the rotation angle of the turntable 201c-2 during single crystal trimming into the length L of the brass tube collimator 102b 2 . Meanwhile, the voltage parameter, the delay emission time and the like of the flash X-ray machine 101 need to be further determined according to specific situations.
Calculating the length X of the lead collimator 102a pb Denoted as L 1
Experiments show that when the anode material of the X-ray diode is a W target, a steel plate with the thickness of 25mm can be penetrated at a position of 2.5m, and when a Mo target is adopted, the intensity change coefficient is as follows: z is Z Mo /Z W ＝42/74
According to the X-ray attenuation formula:
wherein: k is a constant, Z is an atomic number of a metal absorbing X-rays, X is a thickness of a steel plate, and λ is a wavelength of X-rays. Further for point sources, the intensity of the X-rays is inversely proportional to the square of the source distance, i.e.:
distance r from anode target surface in flash X-ray tube to X-ray tube window in the system pb1 =25 mm, knowing r Fe1 =2500 mm, for steel, I Fe1 When r is Fe1 Intensity of corresponding X-ray at 2500mm, I Fe2 To be at X-ray distance from the point light source r Fe2 Strength at the point, at this time, the thickness of the penetrated steel plate is marked as F; for lead, I Pb1 When r is pb1 Intensity of X-ray at =25 mm, I pb2 For X-ray distance from point light source r Pb2 Strength at where r Fe2 ＝r Pb2 。
The change in the atomic number Z is only considered, irrespective of the change in the wavelength lambda from W to Mo targets. According to formulas (1), (2), (3) and (4), the following formulas are obtained:
I 0 exp[-kλ 3 Z Fe 3 ρ Fe F]/2500 2 ＝(42/74)I 0 exp[-kλ 3 Z Pb 3 ρ Pb x pb ]/25 2 (5)
the length X of the lead collimator required by completely absorbing scattered flash X-rays can be calculated pb Denoted as L 1 。
The crystal plane of the Ge single crystal is selected to be the (220) plane, the lattice parameter and the interplanar spacing d are known, the lattice constant a= 0.5658nm of Ge, according to the following formula:
it can be calculated that d= 0.3267nm, the flash X-ray machine 101 uses a Mo target, and the wavelength lambda is obtained by inquiry Mo-Kα1 Wavelength lambda = 0.07093nm Mo-Kα2 = 0.07135nm, and K is calculated according to bragg's law (7) α1 Rays, K α2 Bragg angle θ of ray 1 And theta 2 。
2dsinθ＝nλ (7)
The two are subtracted to obtain K α1 Ray sum K α2 The angle difference θ of the bragg angles of the rays, i.e. the difference between the diffraction angles, is 0.06 °. Then, the sum L of the lengths of the lead collimator 102a and the brass tube collimator 102b is calculated according to the width d (0.3 mm) of the lead slit, namely:
L＝d/tanθ (8)
the length L of the lead collimator 102a is subtracted from the length L 1 The length L of brass tube collimator 102b can be obtained 2 。
In the adjusting process, the specific operation steps are as follows:
1) First, the adjustment of the flash X-ray diffraction optical path is performed. The Ge monocrystal is first rotated and coarse regulated to the diffraction angle theta of K alpha 1 ray with horizontal direction 1 The course of the coarse tuning is as follows:
the pitching stage 201c-1 is first finely tuned to ensure that the Ge single crystal contained in the monochromic unit 201 is always in the vertical direction, and then the collimating unit 1 is used02 determining the optical path axis of the incident light, adjusting the crystal position to make the surface normal coincide with the optical path axis, determining the reference position, and finally adjusting the crystal position to make the angle between the surface and the optical path axis be at the diffraction angle theta of K alpha 1 ray 1 In the vicinity, the angle is determined as the initial diffraction angle.
2) The direction in which the Ge single crystal is rotated after rough adjustment is not very precise, and fine adjustment of the Ge single crystal is required.
The fine tuning process is as follows:
the flash X-ray machine is first caused to generate flash X-rays, which then pass through the lead slit, the lead collimator 102a and the brass tube collimator 102b, and then enter the Ge single crystal in the monochromic unit 201. According to the calculated diffraction angle difference theta (smaller than 0.1 DEG) between the K alpha 1 ray and the K alpha 2 ray, the rotating table 201c-2 is adjusted by using the fine tuning rod 201c-3 in cooperation with the digital display, so that the angle of each rotation of the rotating table 201c-2 is ensured not to exceed the angle theta, then the optimal diffraction position of the Ge monocrystal is judged according to the brightness change of diffraction imaging on the imaging plate 301, namely, when the number of diffracted photons received on the imaging plate is the largest, and the optimal diffraction position is recorded. Each time a flash X-ray diffraction experiment is performed, the Ge single crystal in the single-color cell 201 needs to be rotated to an optimal diffraction position.
3) After the position of the Ge single crystal was adjusted, a flash X-ray diffraction experiment was performed. The diffraction direction of the diffraction line is calculated according to the crystal plane direction of the crystal to be measured, and then the imaging plate 301 is adjusted so as to be in the direction of optimally receiving the diffraction line.
4) The external controller and high voltage pulse generator are then adjusted so that the flash X-ray diode emits high energy flash X-rays with exposure times on the order of nanoseconds.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
Claims (6)
1. A high-energy monochromatic flash X-ray diffraction imaging method is characterized in that: having a high energy monochromatic flash X-ray diffraction imaging system, comprising,
the X-ray emission collimation module (100) comprises a flash X-ray machine (101) and a collimation unit (102), wherein the flash X-ray machine (101) emits X-rays, and the collimation unit (102) is connected with the flash X-ray machine (101) and is positioned on the X-ray emission end along a line;
the collimating unit (102) comprises a lead collimator (102 a), a brass tube collimator (102 b) and a glass capillary tube (102 c), wherein the brass tube collimator (102 b) is connected to the outlet end of the lead collimator (102 a), and the glass capillary tube (102 c) is arranged in the inner cavity of the lead collimator (102 a) and is communicated with the inlet end and the outlet end of the lead collimator;
attaching a lead slit with the width of 0.3mm at the joint of the flash X-ray diode and the lead collimator (102 a);
the single-color separation module (200) is arranged along the X-ray line and comprises a single-color unit (201) and an emergent unit (202), wherein the single-color unit (201) is connected with the emergent unit (202), and the emergent unit (202) is positioned at one side of the emergent end of the single-color unit (201);
the single-color unit (201) comprises a brass cylinder (201 a), a single crystal (201 b) and an angular platform (201 c), wherein the single crystal (201 b) is positioned in an inner cavity of the brass cylinder (201 a) and is placed on the top of the angular platform (201 c), and the bottom of the angular platform (201 c) extends outside the brass cylinder (201 a) through the side wall of the brass cylinder;
the emergent unit (202) comprises an emergent brass tube (202 a), a transverse moving plate (202 b) and a longitudinal moving plate (202 c), wherein the transverse moving plate (202 b) and the longitudinal moving plate (202 c) are respectively and movably matched with two ends of the emergent brass tube (202 a), and one end, matched with the transverse moving plate (202 b), of the emergent brass tube (202 a) is connected with the emergent end of the brass cylinder (201 a);
the diffraction imaging module (300) is positioned along the emergent direction of the single-color separation module (200) and comprises an imaging plate (301) and a rotating seat (302), wherein the rotating seat (302) is arranged at the bottom end of the imaging plate (301);
the method also comprises the following diffraction imaging operation steps:
determining suitable experimental parameters, including selecting the single crystal (201 b) and a flash X-ray tube anode material;
calculating the length of the collimating unit (102) according to the selected material, and respectively calculating diffraction angles of the K alpha 1 ray and the K alpha 2 ray and the difference value of the diffraction angles of the K alpha 1 ray and the K alpha 2 ray;
constructing a diffraction imaging model of the monochromatic flash X-ray according to the calculated value;
-determining, by adjustment, that the single crystal (201 b) is in an optimal diffraction position, using the model;
the rotation base (302) is adjusted so that the X-rays after monochromatic separation obtain an optimal diffraction imaging effect on the imaging plate (301).
2. The high energy monochromatic flash X-ray diffraction imaging method as claimed in claim 1, wherein: the flash X-ray machine (101) comprises a high-voltage pulse generator and a flash X-ray tube, wherein X-rays emitted by the flash X-ray tube comprise K alpha 1 rays, K alpha 2 rays and K beta rays.
3. The high energy monochromatic flash X-ray diffraction imaging method as claimed in claim 2, wherein: the angular platform (201 c) comprises a pitching platform (201 c-1), a rotating platform (201 c-2) and a fine tuning rod (201 c-3), wherein the pitching platform (201 c-1) is fixed on the top of the rotating platform (201 c-2), and the fine tuning rod (201 c-3) is connected to the rotating axis of the rotating platform (201 c-2).
4. A method of high energy monochromatic flash X-ray diffraction imaging as claimed in claim 3, wherein: a limiting rod and a connecting groove are arranged at one end of the emergent brass tube (202 a) matched with the transverse moving plate (202 b), and a U-shaped chute is arranged at one end of the emergent brass tube matched with the longitudinal moving plate (202 c);
a longitudinal slit (202 b-1) is formed in the middle of the side wall of the transverse moving plate (202 b);
a transverse slit (202 c-1) is formed in the middle of the side wall of the longitudinal moving plate (202 c).
5. The high energy monochromatic flash X-ray diffraction imaging method as claimed in claim 4, wherein: according to the calculated length of the collimation unit (102), the lengths of the lead collimator (102 a) and the brass tube collimator (102 b) are respectively calculated, and the outer diameter of the brass tube collimator (102 b) is far smaller than the outer diameter of the lead collimator (102 a), and the inner diameters of the lead collimator and the brass tube collimator are the same.
6. The high energy monochromatic flash X-ray diffraction imaging method as claimed in claim 5, wherein: during the adjustment, the pitching stage (201 c-1) is firstly adjusted in a rough mode, so that the single crystal (201 b) is kept vertical to the horizontal plane;
and then driving the rotary table (201 c-2) by fine tuning the fine tuning rod (201 c-3) and determining that the single crystal (201 b) is at an optimal diffraction position by matching with the imaging plate (301).
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