阅读说明：本技术 一种具有高分辨率和高单色性的x射线光学成像系统 (X-ray optical imaging system with high resolution and high monochromaticity ) 是由 伊圣振 王占山 马爽 于 2021-06-09 设计创作，主要内容包括：本发明涉及一种具有高分辨率和高单色性的X射线成像光学系统,包括多通道KB成像物镜和探测器,所述多通道KB成像物镜的输出侧与探测器之间放置有N块平面晶体,其中,N≥1,所述平面晶体的数量与单色能点的数量相同,所述多通道KB成像物镜的各通道反射光束之间具有平行出射的光路特性。与现有技术相比,本发明能够解决现有多通道KB结构配合平面晶体元件过程中存在的问题,同时实现高空间分辨和高单色性的目的,本发明提出的多能点X射线成像系统,基于各成像通道相互平行出射的光路排布,易于实现成像物镜与平面晶体匹配时的角度姿态控制,降低角度偏差造成的实际诊断能点相对设计能点的漂移,进而有效提高诊断结果的可靠性。(The invention relates to an X-ray imaging optical system with high resolution and high monochromaticity, which comprises a multi-channel KB imaging objective lens and a detector, wherein N planar crystals are arranged between the output side of the multi-channel KB imaging objective lens and the detector, N is more than or equal to 1, the number of the planar crystals is the same as the number of monochromatic energy points, and the reflected light beams of each channel of the multi-channel KB imaging objective lens have the light path characteristic of parallel emergent light. Compared with the prior art, the multi-energy point X-ray imaging system can solve the problems in the process that the existing multi-channel KB structure is matched with a planar crystal element, and simultaneously achieves the purposes of high spatial resolution and high monochromaticity.)

1. An X-ray imaging optical system with high resolution and high monochromaticity comprises a multi-channel KB imaging objective lens and a detector, and is characterized in that N planar crystals are arranged between the output side of the multi-channel KB imaging objective lens and the detector, wherein N is more than or equal to 1, the number of the planar crystals is the same as the number of monochromatic energy points, and parallel emergent light path characteristics are formed among all channel reflected light beams of the multi-channel KB imaging objective lens.

2. The optical system of claim 1, in which the object-image distances of each channel in the multi-channel KB imaging objective are the same.

3. The optical system as claimed in claim 2, wherein the object-image distance of each channel in the multi-channel KB imaging objective is specifically as follows:

wherein u is the object image distance, R is the curvature radius of the reflector, M is the magnification of the reflector, and theta is the grazing incidence angle of the reflector.

4. The optical system of claim 3, wherein the two mirrors in the multi-channel KB imaging objective lens are oppositely arranged and satisfy the following relation in the imaging direction:

wherein, R is the curvature radius of the reflector, theta is the grazing incidence angle of the reflector, M is the magnification factor of the reflector, and L' is the light path interval of the reflector, namely the interval between any two channel reflected light beams.

5. The X-ray imaging optical system with high resolution and high monochromaticity according to claim 4, wherein the angle between the detector recording surface and the reflected beam of the multi-channel KB imaging objective lens is 2 theta when N is 1.

6. The X-ray imaging optical system with high resolution and high monochromaticity according to claim 1, wherein when N is 1, the interval between any two reflected beams of the multi-channel KB imaging objective lens is the same as the interval of the detector recording surface.

7. An X-ray imaging optical system having high resolution and high monochromaticity according to claim 1, characterized in thatWhen N is more than 1, each channel of the multi-channel KB imaging objective lens is divided into N groups, and the N groups are respectively at different angles alpha₁～α_nIncident on the N planar crystals.

8. The optical system of claim 7, wherein the angle between the detector recording surface and the reflected beam of the multi-channel KB imaging objective lens is α > 1 when N > 1₁+α_n。

9. The optical system as claimed in claim 7, wherein when N > 1, the distance between any two reflected beams of the multi-channel KB imaging objective lens is as follows:

wherein L' is the distance between two groups of channel reflected beams, L is the interval of the recording surface of the detector, m is the distance between the center of the detector and the channel reflected beam at the nearer side, and alpha_iAnd alpha_mThe channels that are closer to and farther from the center of the detector reflect the angle of incidence of the light beam at the planar crystal.

10. The optical system of claim 7, in which when N > 1, if any two reflected beams of the multi-channel KB imaging objective lens are at the same angle α_iThe distance between the two reflected light beams is as follows:

L'＝Lsin(2α_i-α₁-α_n)

wherein, L' is the interval between two groups of channel reflected light beams, and L is the interval of the recording surface of the detector.

Technical Field

The invention relates to the technical field of laser plasma X-ray imaging, in particular to an X-ray optical imaging system with high resolution and high monochromaticity.

Background

The method is an important research content in the fields of High Energy Density Physics (HEDP) and Inertial Confinement Fusion (ICF) for carrying out high-quality imaging diagnosis on important information such as spatial distribution, time evolution, energy spectrum characteristics and the like of plasmas. The multi-channel grazing incidence X-ray imaging objective lens is matched with the time-resolved framing camera, each imaging channel corresponds to the transient information of the plasma at a certain moment, and the two-dimensional transient evolution behavior of the plasma, namely the spatial distribution and the time evolution information, can be obtained. The curved crystal imaging can obtain the high-energy spectrum resolution two-dimensional space distribution of the plasma at a certain energy point, and is mainly suitable for the single-energy imaging of diagnostic tracing or doping element X-ray characteristic lines. If a multi-channel X-ray imaging objective lens (mainly a multi-channel KB microscope at present) with high spatial resolution can be coupled with a planar crystal light splitting element with high spectral resolution, a plurality of high spatial resolution and high monochromaticity images responding to the same energy point can be obtained, and time-resolved signal recording can be completed by combining image surface recording equipment such as a framing camera.

However, the coupling of KB (Kirkpatrick-Baez) microscopes to planar crystals presents a serious technical obstacle: the microstrip recording surfaces of the framing camera are distributed along a certain interval, which requires that image point arrangement of each channel forming of the KB microscope is consistent with the microstrip interval, the conventional multichannel KB structure is that large-curvature-radius ultra-smooth spherical reflectors are opposite in pairs and are orthogonally arranged in the meridian and sagittal directions in sequence, each imaging channel is subjected to one-dimensional focusing reflection imaging of one reflector in the meridian and sagittal directions, all the imaging channels mutually utilize the reflectors in imaging, and finally form a matrix-arranged image point combination on the detector recording surface, a light path structure with eight imaging channels is shown in figure 1 (the label 1 is an object point, the label 2 is a supporting cone core assembly leaning body which comprises six different reflectors in total from M1 to M6, wherein M1, M2, M5 and M6 are in the meridian direction, M3 and M4 are in the sagittal direction, and the label 3 is the framing camera, namely a detector), the light path arrangement structure of the multi-channel KB structure can only realize the regulation and control of the space interval of image points by adjusting the object-image distance and other modes, and can not control the relative included angle and the interval of light beams of each channel in the transmission process, and the X-ray light paths emitted by each channel form images on different positions of an image plane in different space ranges and included angles, so that if a planar crystal is introduced through each channel to carry out monochromatic imaging, the incident angles of the channels are different after the planar crystal is introduced, the angle posture is difficult to control, and meanwhile, the spatial position of a reflected monochromatic image is greatly deviated, so that the ideal matching of the arrangement of the image points of each channel and the interval of the recording surface of a framing camera is difficult to realize by the conventional multi-channel KB microscope and planar crystal, and the feasibility is not available on the light path structure. In addition, since the planar crystal element operates based on the bragg diffraction principle: where d is the lattice constant, λ is the operating wavelength, and θ is the bragg angle (i.e., grazing incidence angle), and HEDP and ICF physical experiments typically image characteristic X-rays radiated from a target material, such as Cu with a K α line energy point of 8.04keV (corresponding to a wavelength of 0.154nm) and a spectral resolution λ/Δ λ -tan θ/Δ θ. The small deviation delta theta of the working angle can cause the monochromatic X-ray energy points reflected by the planar crystal to deviate from the interested characteristic X-ray energy points, so that the monochromatic energy points corresponding to all imaging channels have large difference, and meanwhile, the imaging light intensity is sharply reduced, even no signal exists. Therefore, from the aspect of diagnostic effect, the consistency of the working energy point and the light intensity of each image is difficult to be well ensured, and the data accuracy of diagnostic measurement is inevitably seriously influenced.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned drawbacks of the prior art, and providing an X-ray optical imaging system with high resolution and high monochromaticity, so as to solve the problems of the conventional multichannel KB structure in cooperation with a planar crystal device, and achieve the objectives of high spatial resolution and high monochromaticity.

The purpose of the invention can be realized by the following technical scheme: an X-ray imaging optical system with high resolution and high monochromaticity comprises a multi-channel KB imaging objective lens and a detector, wherein N planar crystals are arranged between the output side of the multi-channel KB imaging objective lens and the detector, N is larger than or equal to 1, the number of the planar crystals is the same as the number of monochromatic energy points, and parallel emergent light path characteristics are arranged among all channel reflected light beams of the multi-channel KB imaging objective lens.

Further, the object-image distances of all channels in the multi-channel KB imaging objective lens are the same.

Further, the object-image distance of each channel in the multi-channel KB imaging objective lens is specifically as follows:

wherein u is the object image distance, R is the curvature radius of the reflector, M is the magnification of the reflector, and theta is the grazing incidence angle of the reflector.

Further, in the multichannel KB imaging objective lens, two oppositely arranged mirrors meet the following relation in the imaging direction:

wherein, R is the curvature radius of the reflector, theta is the grazing incidence angle of the reflector, M is the magnification factor of the reflector, and L' is the light path interval of the reflector, namely the interval between any two channel reflected light beams.

Further, when N is 1, an included angle between the detector recording surface and a reflected light beam of the multi-channel KB imaging objective lens is 2 θ.

Further, when N is 1, the pitch between any two reflected beams of the multi-channel KB imaging objective lens is the same as the interval of the detector recording surface.

Further, when N is more than 1, the reflected light beams of the channels of the multi-channel KB imaging objective lens are divided into N groups which are respectively at different angles alpha₁～α_nIncident on the N planar crystals.

Further, when N is more than 1, the included angle between the recording surface of the detector and the reflected beam of the multichannel KB imaging objective lens is alpha₁+α_n。

Further, when N is greater than 1, in the multi-channel KB imaging objective lens, if any two reflected light beams are incident on different planar crystals at different angles, the distance between the two reflected light beams is specifically:

wherein L' is the distance between two groups of channel reflected beams, L is the interval of the recording surface of the detector, m is the distance between the center of the detector and the channel reflected beam at the nearer side, and alpha_iAnd alpha_mThe channels that are closer to and farther from the center of the detector reflect the angle of incidence of the light beam at the planar crystal.

Further, when N > 1, in the multi-channel KB imaging objective, if any two channels of the reflected light beams are at the same angle α_iThe distance between the two reflected light beams is as follows:

L'＝Lsin(2α_i-α₁-α_n)

wherein, L' is the interval between two groups of channel reflected light beams, and L is the interval of the recording surface of the detector.

Compared with the prior art, the invention has the following advantages:

the invention adopts the multi-channel KB imaging objective lens which is emergent in parallel to be matched with one or more planar crystals, so that the interval arrangement of the light paths of the channels before and after the planar crystals are incident and emergent is not changed, the angle coupling and the image point interval coupling between the channels and the planar crystals and a detector are favorably realized, the problems existing in the process that the conventional multi-channel KB structure is matched with planar crystal elements are solved, and the purposes of high spatial resolution and high monochromaticity can be realized.

The invention adopts the multichannel KB imaging objective lens which is emitted in parallel, and the incident angles of all channels on the planar crystal are the same no matter what kind of change occurs to the planar crystal, so that the invention can realize good response to the same energy point, can effectively improve the consistency of response energy points, and also brings good effect for practical application.

Thirdly, according to the number requirement of the monochromatic energy points, the planar crystals with the corresponding number are arranged to serve as light splitting elements, and high spatial resolution and high monochromaticity imaging of a single energy point or a plurality of energy points can be achieved; the included angle between the recording surface of the detector and the reflected light beam of the multichannel KB imaging objective lens is correspondingly set by combining the grazing incidence angle of the reflector in the multichannel KB imaging objective lens and the angle of the incident light beam to the plane crystal, so that the image recorded by the detector can be effectively prevented from being distorted; the invention also correspondingly sets the relationship between the distance between the two reflected light beams and the distance between the recording surfaces of the detectors so as to further ensure that each image point is matched with the detector.

Drawings

FIG. 1 is a schematic diagram of the optical path structure of a prior art multi-channel KB objective;

FIG. 2 is a microstrip layout diagram of a framing camera coupled with the four-channel KB system in an embodiment;

FIG. 3 shows the spatially resolved simulation results of the four-channel KB system of the embodiment;

FIG. 4 is a schematic diagram of the optical path arrangement of the four-channel KB system in the meridional direction in the embodiment;

FIG. 5 is a light path arrangement in the sagittal direction for the four-channel KB system in an embodiment;

FIG. 6a is a first measured plot of Bragg angle for a mica crystal coupled with a four-channel KB system in accordance with an example;

FIG. 6b is a second measured Bragg angle curve for a mica crystal coupled with the four-channel KB system of the example;

the notation in the figure is: 1. object point, 2, cone core, 3, detector.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples

The invention aims to solve the problems in the process of matching the conventional multichannel KB structure with a planar crystal element, and provides an X-ray imaging system with high spatial resolution and high monochromaticity. The invention takes a multi-channel X-ray KB structure with the parallel emergent light path characteristic of each channel reflected light beam as a multi-channel imaging objective lens, and places one or more plane crystals as light splitting elements in front of an image plane (namely between the output side of the multi-channel KB objective lens and a detector) according to the requirement of the number of monochromatic energy points. The spatial resolution of each channel of the KB microscope is obviously changed along with the position of a field of view, and the imaging in the central field of view with the best resolution conforms to the following formula:

where u is the object distance, R is the radius of curvature, M is the magnification, and θ is the grazing incidence angle. Since the multichannel KB microscope needs to image the same object point and be recorded by the same detector, each channel should have the same object-image distance, and since the mirrors are arranged orthogonally in sequence, the object distance and the image distance of each mirror have a numerically substantially determined variation relationship, so that in practice, u and M of each mirror should still be considered as a certain value. Under the requirement of the formula (1), a certain curvature radius R of the two oppositely arranged reflectors in the imaging direction has the following relationship with the grazing incidence angle theta, the magnification factor M and the light path distance L':

the formula (2) enables the X-rays emitted by the object point to be emitted in parallel between X-ray paths after passing through the imaging objective, and the X-rays still accord with the formula (1) for maintaining high-spatial resolution imaging. In order to ensure that all channels have the same object-image distance relationship and images recorded by the framing camera are not distorted, when only aiming at a single energy point, the recording surface of the detector is perpendicular to an incident X-ray beam as much as possible, namely the recording surface of the detector and an X-ray emergent light path (namely a reflected beam of a multi-channel KB imaging objective lens) are arranged at an included angle of 2 theta;

in order to ensure that the image points are matched to the image plane detection device, the distance L' between the parallel exit light paths has the same spacing L as the recording plane of the detection device, i.e. L ═ L. On the basis of the structure, even if the angle alpha of the crystal is changed or different plane crystals are replaced, the incident angle of each imaging channel to the plane crystals is consistent, and the image point interval L' is the same as L, so that high monochromaticity imaging of another energy point can be realized. Therefore, the invention realizes the high monochromaticity imaging of the same energy point E by controlling the grazing incidence angle theta and the curvature radius R of the reflector and realizing the parallel emergent light path characteristics of each channel to enable the parallel emergent light paths to be incident on the planar crystal at the same angle alpha and be reflected.

When aiming at a plurality of different energy points, N pieces of plane crystals are placed in front of the image surface to be used as light splitting elements, and each channel light path is divided into N groups which are respectively at different angles alpha₁To alpha_nIncident on N plane crystals to realize the alignment of N energy points E₁To E_nIn order to reduce the distortion caused by the inclination of the recorded image, the recording surface of the detector and the X-ray emergent light path form alpha₁+α_nAnd placing the angle. Wherein for angle alpha_iAnd alpha_mAnd if the expected interval on the image plane detector is L, the interval L' of the two groups of X-ray channel light paths which are emitted in parallel meets the following relationship:

wherein m is the distance between the center of the image plane detector and the near side group of X-ray channel light paths, and alpha_iAnd alpha_mThe incidence angles of the X-ray channel light paths of the group of the closer side and the farther side on the plane crystal respectively;

for at the same angle alpha_iAnd if the expected interval on the image plane detector is L, the interval L' of the two groups of X-ray channel light paths which are emitted in parallel meets the following relation:

L'＝Lsin(2α_i-α₁-α_n) (4)

by adopting the technical scheme, the multichannel KB objective lens is used for the Z-pinch device, so that characteristic lines with the energies of 653.6eVeV and 665.7eV are subjected to imaging diagnosis on a tracer element oxygen-hydrogen-like line and a tracer element helium-like line in the target pill implosion compression process, and the energy spectrum resolution of +/-5 can be required to be realized at the energy point positions of the two characteristic lines. The number of imaging channels designed in this embodiment is four. In order to cooperate with the framing camera at the image plane position to realize time resolution, as shown in fig. 2, after each imaging channel is subjected to single color by the crystal, the image point position should be located at the central position of two microstrips of the framing camera, that is, 4 image points are symmetrically distributed on the microstrips by 2 × 2.

Mica is adopted as a planar crystal in the embodiment, and the curvature radius of the designed KB imaging objective lens is about 60m, the working grazing incidence angle is about 1.9 degrees, the lens length is 30mm, and the magnification is about 1.8 times. The change of the system spatial resolution obtained by simulation of the ZEMAX optical design software is shown in FIG. 3, and the spatial resolution in the sagittal direction is substantially the same as that in the meridional direction. It can be seen that the spatial resolution within the field of view of + -1.5 mm is better than 40 μm, the spatial resolution within the field of view of + -1 mm is better than 25 μm, and the optimal spatial resolution of the central field of view can reach the level of 10 μm. The geometric light collection efficiency of the objective lens is about 4.1 multiplied by 10^-7sr, considering near 100% efficiency at the 660eV energy point, the effective collection efficiency of the system is not significantly reduced compared to the geometric efficiency.

Mica is a commonly used single-color crystal at energy points around 500 eV. In order to simplify the coupling difficulty of the plane mica and the imaging objective lens, the X rays of four channels of the imaging objective lens are emitted in parallel. Fig. 4 shows the arrangement of the optical paths of the mirrors a and C in the meridian direction, which corresponds to the monochromatization of the same energy point by the same mica plate. X-rays emitted by the object point are respectively emitted in parallel by a distance (13mm) which is in accordance with the micro-strip interval of the framing camera after passing through the two reflectors. The curvature radius and the grazing incidence angle of the first reflector are respectively R₁And theta₃Since the two mirrors image the same object point and exit in parallel at a specific interval, the grazing incidence angle (θ) of the second mirror C in the subsequent stage₃) Grazing incidence angle (theta) with the first mirror A₁) CorrelationRadius of curvature (R) of second mirror C₃) And ultimately also determined therefrom to satisfy the KB imaging formula requirements, resulting in R₃And R₁The difference in the values.

In order to reduce the processing difficulty of the spherical reflector and improve the consistency of the imaging relation; the four KB objective lenses are supposed to adopt two groups of curvature radiuses, namely the preorders of the meridional direction and the sagittal direction and the curvature radiuses of the two subsequent reflectors are respectively the same, namely R₁＝R₃And R₂＝R₄. Fig. 5 shows the optical path arrangement of the four-channel KB objective lens in the sagittal direction, where two micas monochromate two energy points 653.6eV and 665.7eV, respectively, and finally correspond to the same microstrip of the framing camera at the image plane position. The X-ray spacing before mica reflection was about 17.15mm, and the spacing at the image plane position after mica reflection was 20 mm. The distance of the turns is about 365 mm.

The optical structure parameters of the resulting four-channel KB objective lens are shown in table 1. The two groups of spherical mirrors to be processed have the curvature radii of 60m and 53.639m respectively and the surface caliber of 30 x 30 mm. The working distance of the system is 4.0m, and after the mica crystal is turned, the total length of the system is about 3.7 m.

TABLE 1

Theoretical Bragg angles of the mica crystals corresponding to 653.6eV and 665.7eV are about 71.7 degrees and 68.8 degrees respectively, actual Bragg angles are different according to the production place, material and the like of mica, and the Bragg angles of the used mica crystals are measured in a synchrotron radiation device, and as shown in fig. 6a and 6b, the thickness of the mica crystals is 0.2 mm. It can be seen that there is a good discrimination between the measured Bragg angles of the mica platelets at the two energy points. The measured Bragg angles are all about 0.1 deg. lower than the theoretical values. The angular bandwidths (FHWM) at 665.7eV and 653.6eV are about 0.35 ° and 0.15 °, respectively, and the corresponding energy spectral resolution E/Δ E is θ/Δ θ, which is about 200 and 460, respectively, scaled to Δ E of about ± 1.6eV and ± 0.7eV, respectively, i.e., meets the ± 5eV specification.

In summary, the technical scheme provided by the invention adopts a multichannel X-ray KB structure with a reflecting surface having a specific curvature radius as a multichannel imaging objective lens, so that X-rays emitted by an object point are emitted in parallel from X-ray optical paths of different channels after passing through the imaging objective lens while realizing high spatial resolution, and have specific distance intervals; then one or more planar crystals are placed in front of an image surface as a light splitting element, each planar crystal has a specific spatial attitude, and light paths of all channels parallelly emergent through an imaging objective are incident on the planar crystal at the same or different angles and are reflected, wherein all imaging channels incident on the same planar crystal at the same angle work at the same energy point, and all imaging channels incident on the planar crystals at different angles work at different energy points of respective response; and finally, the high spatial resolution and high monochromaticity effect of the imaging result under multiple energy points are realized on the image plane. The multi-energy point X-ray imaging system provided by the invention is arranged by the light paths of the imaging channels which are parallel to each other, so that the angle posture control during the matching of the imaging objective lens and the planar crystal is easy to realize, the drift of the actual diagnosis energy point relative to the designed energy point caused by the angle deviation is reduced, and the reliability of the diagnosis result is effectively improved.