Variable operating point grazing incidence x-ray microscopy optical structure

Abstract

The application discloses a variable working point grazing incidence X-ray microscopic imaging optical structure and relates to the technical field of microscopic imaging. The technical scheme is as follows: the structure comprises an object point, a first reflector, a second reflector, a third reflector and an image plane; the object point is located in front of the first reflector, and the image plane is located behind the third reflector; the first reflector, the second reflector and the third reflector are placed in series and work under the condition of a small grazing incidence angle; the first reflector and the second reflector form a double-mirror structure for high-resolution imaging, and the third reflector for adjusting the working point is arranged in the light path at the rear end of the second reflector. The application can effectively make up for the deficiency that the working point of the existing grazing incidence reflective optical system is difficult to change once the design is completed; the optical structure of the application makes the diagnostic system more adaptable, has the characteristics of high spatial resolution and continuously adjustable working point, and can better serve X-ray microscopic imaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microscopic imaging technology, more particularly, it relates to a variable working point grazing incidence X-ray microscopic imaging optical structure. BACKGROUND

[0002] Laser inertial confinement fusion (ICF, Inertial Confinement Fusion) is one of the effective technical approaches to develop controlled nuclear fusion in peacetime. The implosion target pellet containing deuterium-tritium thermonuclear fuel is compressed to a spatial scale of several tens of microns in a very short time, and the material state reaches a high temperature and high pressure state similar to the interior of a star.

[0003] High-precision X-ray microscopic imaging optical instruments are the key to a deep understanding of the implosion process and quantitative inversion of implosion parameters. Common X-ray imaging diagnostic equipment mainly includes pinhole cameras, Kirkpatrick-Baez (KB) microscopes, and spherical bending crystals. Among them, the resolution of the pinhole camera is limited by the effective aperture, generally 8-10 μm, and it is difficult to achieve high-resolution microscopic imaging. KB microscopes and spherical bending crystals are generally designed to respond to specific working points, and once the design and development of the diagnostic equipment are completed, it will be difficult to change the working point of the system again.

[0004] High-quality implosion process diagnosis requires high-resolution, adjustable working point X-ray microscopic imaging optical systems. Such systems can play an important role in back-light photography or self-luminous imaging of implosion target pellets. The design of optical structures with variable working points can make the optical system adapt to X-ray radiation at different energy points, making the diagnostic system configuration more flexible, while avoiding the development of multiple sets of X-ray imaging diagnostic equipment.

[0005] Existing grazing incidence reflective optical systems or spherical bending crystals are generally designed to respond to specific working points, and once the equipment is developed, the working point cannot be changed, and it cannot be applied to multiple experimental situations, making it difficult to further adapt to the experimental needs of different energy point back-light target diagnosis. SUMMARY

[0006] The purpose of the present application is to provide a variable working point grazing incidence X-ray microscopic imaging optical structure, which can effectively make up for the deficiency of the existing grazing incidence reflective optical system that cannot change the working point, making the diagnostic system more adaptable, with high spatial resolution and continuously changing working point characteristics, and better serving X-ray microscopic imaging.

[0007] The technical purposes are achieved by the following technical solutions: a variable working point grazing incidence X-ray microscopic imaging optical structure, comprising an object point, a first mirror, a second mirror, a third mirror and an image plane; the object point is located in front of the first mirror, and the image plane is located behind the third mirror; the first mirror, the second mirror and the third mirror are placed in series and work under the condition of a small grazing incidence angle; the first mirror and the second mirror constitute a double-mirror structure for high-resolution imaging, and the third mirror for working point adjustment is placed in the optical path at the rear end of the second mirror.

[0008] The application is further provided as follows: a rectangular coordinate system is established with the object point as the origin, the object point points to the image plane as the positive direction of the X axis, the object point vertically upwards is the positive direction of the Z axis, and the placement position of the third mirror in the optical path is (D_x, D_z); the calculation formula of the vertical coordinate D_z of the third mirror in the optical path is as follows:

[0009]

[0010] Wherein, M is the system magnification, u is the distance from the object point to the center of the first mirror, D_x is the horizontal coordinate of the center of the third mirror, C_x is the horizontal coordinate of the center of the second mirror, and θ1 is the grazing incidence angle of the first mirror;

[0011] The calculation formula of the grazing incidence working angle θ3 of the third mirror is as follows:

[0012]

[0013] Wherein, θ1 is the grazing incidence angle of the first mirror, M is the system magnification, θ axis_3 is the included angle between the third mirror and the central axis;

[0014] The grazing incidence working angle of the third mirror is adjusted to realize continuous adjustment of the system working point, and the formula is as follows:

[0015]

[0016] Wherein, E is the working point of the system, d is the period thickness of the X-ray period multilayer film, θ3 is the grazing incidence angle of the third mirror, and δ is the angle correction small amount;

[0017] The vertical distance of the image point generated after three reflections from the central axis in the image plane is calculated, and the calculation formula is as follows:

[0018] E_z=tan2θ3[(M+1)u-D_x] (4)

[0019] Wherein, E_z is the vertical distance of the image point from the central axis in the image plane, theta 3 is the grazing incidence angle of the third mirror, M is the system magnification, u is the distance from the object point to the center of the first mirror, D_x is the distance from the object point to the center of the third mirror;

[0020] The system response efficiency considers the light collection solid angle and the efficiency of three times of grazing incidence reflection of the optical configuration geometry, and the calculation formula of the system response efficiency of the optical structure is as follows:

[0021]

[0022] Wherein, w is the effective mirror width; theta 1 is the grazing incidence angle of the first mirror; L1 is the mirror length of the first mirror; eta 1, eta 2 and eta 3 are the reflectivities of the first mirror, the second mirror and the third mirror respectively; u is the distance from the object point to the center of the first mirror.

[0023] The application is further provided that: the surface type of the first mirror and the second mirror is spherical-spherical, cylindrical-cylindrical, toric-spherical, hyperbolic cylindrical-elliptical cylindrical or rotational hyperboloid-rotational ellipsoid.

[0024] The application is further provided that: the surface of the first mirror and the second mirror is coated with a wide-band response reflective film.

[0025] The application is further provided that: the third mirror is a plane mirror, and the surface of the third mirror is coated with an X-ray periodic multilayer film with a specific period thickness to achieve narrow-band response.

[0026] In summary, the application has the following beneficial effects: a variable working point grazing incidence X-ray microscopic imaging optical structure composed of three grazing incidence mirrors, wherein the first mirror and the second mirror form a double mirror structure for high-resolution imaging, and have the imaging ability of large field of view and high resolution. The surface type of the first mirror and the second mirror can be spherical-spherical, cylindrical-cylindrical, toric-spherical, hyperbolic cylindrical-elliptical cylindrical, rotational hyperboloid-rotational ellipsoid, etc. The third mirror is a plane mirror coated with an X-ray periodic multilayer film with a narrow response spectrum. By adjusting the working angle of the third mirror, the working point can be continuously adjusted. It can effectively make up for the deficiency that the existing grazing incidence reflection optical system is difficult to change the working point, making the diagnostic system more adaptable, having the characteristics of high spatial resolution and continuously changing working point, and better serving X-ray microscopic imaging. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of the variable working point grazing incidence X-ray microscopic imaging optical structure of the embodiment of the application;

[0028] Figure 2This is an imaging optical path diagram of a grazing-incidence X-ray microscopic imaging optical structure with a variable working energy point according to an embodiment of the present invention;

[0029] Figure 3 is a reflectivity curve of the Pt film coated on the first reflector and the second reflector in an embodiment of the present invention;

[0030] Figure 4 : is the reflectivity curve (8.04 keV) of the W / Si periodic multilayer film coated on the third reflector in the embodiment of the present invention;

[0031] Figure 5 is the reflectivity curve (4.50 keV) of the W / Si periodic multilayer film coated on the third reflector in the embodiment of the present invention;

[0032] Figure 6 This is a graph showing the imaging resolution of the optical structure according to an embodiment of the present invention as a function of the field of view (8.04 keV);

[0033] Figure 7 This is a graph showing the imaging resolution of the optical structure according to an embodiment of the present invention as a function of the field of view (4.50 keV);

[0034] Figure 8 is a diagram of the system response efficiency of the optical structure of an embodiment of the present invention (8.04keV);

[0035] Figure 9 4.50 keV is a diagram of the system response efficiency of the optical structure of an embodiment of the present invention.

[0036] In the figure: 1, object point; 2, first reflector; 3, second reflector; 4, third reflector; 5, image plane. DETAILED DESCRIPTION

[0037] The following is combined with Figures 1-9 The present invention is described in further detail.

[0038] Example: A grazing incidence X-ray microscopy optical structure with variable working energy point, such as Figures 1-9 As shown, it includes an object point 1, a first reflector 2, a second reflector 3, a third reflector 4 and an image plane 5; the object point 1 is located in front of the first reflector 2, and the image plane 5 is located behind the third reflector 4; the first reflector 2, the second reflector 3, and the third reflector 4 are placed in series and work under small grazing incidence angle conditions; the first reflector 2 and the second reflector 3 form a dual-mirror structure for high-resolution imaging, and the third reflector 4 for working energy point adjustment is placed in the optical path at the rear end of the second reflector 3.

[0039] A rectangular coordinate system is established with the object point 1 as the origin, the object point 1 pointing to the image plane 5 is the positive direction of the X axis, the object point 1 vertically upward is the positive direction of the Z axis, and the third mirror 4 is placed at a position (D_x, D_z) in the light path, so that the calculation formula of the vertical coordinate D_z of the third mirror 4 in the light path is:

[0040]

[0041] Wherein, M is the system magnification, u is the distance from the object point 1 to the center of the first mirror 2, D_x is the horizontal coordinate of the center of the third mirror 4, C_x is the horizontal coordinate of the center of the second mirror 3, and θ1 is the grazing incidence angle of the first mirror 2;

[0042] The calculation formula of the grazing incidence working angle θ3 of the third mirror 4 is:

[0043]

[0044] Wherein, θ1 is the grazing incidence angle of the first mirror 2, M is the system magnification, θ axis_3 is the included angle between the third mirror 4 and the central axis;

[0045] The grazing incidence working angle of the third mirror 4 is adjusted to realize continuous adjustment of the system working energy point, and the formula is as follows:

[0046]

[0047] Wherein, E is the working energy point of the system, d is the period thickness of the X-ray periodic multilayer film, θ3 is the grazing incidence angle of the third mirror 4, and δ is the angle correction amount;

[0048] The vertical distance of the image point generated after three reflections from the central axis in the image plane 5 is calculated, and the calculation formula is as follows:

[0049] E_z=tan2θ3[(M+1)u-D_x] (4)

[0050] Wherein, E_z is the vertical distance of the image point from the central axis in the image plane 5, θ3 is the grazing incidence angle of the third mirror 4, M is the system magnification, u is the distance from the object point 1 to the center of the first mirror 2, and D_x is the distance from the object point 1 to the center of the third mirror 4;

[0051] The system response efficiency considers the optical configuration geometric collection solid angle and the efficiency of three times grazing incidence reflection, and the calculation formula of the system response efficiency of the optical structure is as follows:

[0052]

[0053] wherein, w is the effective mirror width; θ1 is the grazing incidence angle of the first mirror 2; L1 is the mirror length of the first mirror 2; η1, η2 and η3 are the reflectivity of the first mirror 2, the second mirror 3 and the third mirror 4 respectively; u is the distance from the object point 1 to the center of the first mirror 2.

[0054] The surface type of the first mirror 2 and the second mirror 3 is spherical-spherical, cylindrical-cylindrical or hyperboloid-ellipsoid. The surfaces of the first mirror 2 and the second mirror 3 are coated with a wide-spectrum response reflective film. The third mirror 4 is a plane mirror, and the surface of the third mirror 4 is coated with an X-ray periodic multilayer film with a specific period thickness to respond to a narrow spectrum. The third mirror 4 has a precise adjustment capability of the pitch angle in the meridian plane, and can adjust the working angle of the incident light on the surface of the third mirror 4.

[0055] In order to further illustrate the proposed variable working point grazing incidence X-ray microscopic imaging optical structure, a set of grazing incidence X-ray microscopic imaging optical structure working at 4.5-11.0 keV energy point is designed. The application purpose is to better meet the needs of variable working point hard X-ray imaging technology or equipment for inertial confinement fusion diagnosis. The technical scheme can conveniently change the working energy point of the grazing incidence imaging, and adapt to more laser target experiment needs.

[0056] Three grazing incidence mirrors are used to achieve the placement of the imaging object point 1, the first mirror 2, the second mirror 3 and the third mirror 4 and the image plane 5 from left to right in sequence. The three mirrors are placed in series and work under the condition of small grazing incidence angle. Among them, the first mirror 2 is a hyperboloid mirror, the second mirror is an ellipsoid mirror, and the third mirror is a plane mirror.

[0057] The technical index of the optical structure system level is shown in Table 1. Among them, the design working energy point of the microscope is 4.5-11.0 keV. The design grazing incidence angle of the first mirror 2 and the second mirror 3 is 0.4°, and the grazing incidence angle of the third mirror 4 is continuously adjustable in the range of 0-1.3°. The system object distance is 500 mm, and the magnification is 10x.

[0058] Table 1 Technical index of optical structure

[0059]

[0060] Table 2 Optical structure parameters of the mirror

[0061]

[0062]

[0063] a The hyperboloid equation is: x2 / a 2 -y 2 / b 2 = 1;

[0064] b Elliptic surface equation is: x 2 / a 2 +y 2 / b 2 = 1;

[0065] The horizontal coordinate D_x of the third mirror 4 is determined as 580.0 mm, and by bringing the optical structure parameters into equation (1), the vertical coordinate D_z of the third mirror 4 can be calculated as 12.5.

[0066] Further assuming that the grazing incidence angle of the third mirror 4 is 1.008°, the rotation angle of the third mirror 4 can be calculated according to equation (2) as 0.862°. According to the coordinates and the rotation angle, the spatial pose of the third mirror 4 can be completely determined.

[0067] Further, the vertical distance E_z of the image point from the center axis on the image plane 5 can be calculated according to equation (4) as 173.2 mm.

[0068] In order to achieve wide spectral response, the surfaces of the first mirror 2 and the second mirror 3 are coated with Pt film, which has the characteristics of small grazing incidence angle, high reflectivity and wide spectral response. The reflectivity curve of the Pt film is as shown in Figure 3 .

[0069] The surface of the third mirror is coated with W / Si periodic multilayer film to achieve energy selection. The film system has the characteristics of large grazing incidence angle, high reflectivity and narrow bandwidth response. The thin film parameters are: the number of periods is 40 pairs, the period thickness is 4.78 nm, and the thickness ratio is 0.5. The thin film reflectivity curve of the mirror at 8.04 keV is as shown in Figure 4 , and the corresponding grazing incidence angle is 1.008°; the thin film reflectivity curve of the mirror at 4.5 keV is as shown in Figure 5 , and the corresponding grazing incidence angle is 1.8°.

[0070] According to equation (3), the corresponding relationship table of the grazing incidence angle and the working energy point and the image point vertical coordinate can be further obtained. By rotating the third mirror, the continuous adjustment of the working energy point can be realized.

[0071] Table 3 Comparison table of the grazing incidence angle θ3 of the third mirror and the working energy point and the image point vertical coordinate

[0072]

[0073] The imaging performance of the optical structure can be verified by ray tracing. The system spatial resolution of the optical structure at 8.04 keV energy point varies with the field of view as shown in the accompanying Figure 6 The system spatial resolution of the optical structure at 4.5 keV energy point varies with the field of view as shown in the accompanying Figure 7 It can be seen that the resolution of the optical structure is better than 1.29 μm within the field of view of ±0.5 mm, and better than 4.43 μm within the field of view of ±1 mm.

[0074] The system response efficiency of the optical structure can be calculated according to formula (5). The system response efficiency of the optical structure at 8.04 keV energy point varies as shown in the accompanying Figure 8 The response peak is 9.42×10 -7 sr. The system response efficiency of the optical structure at 4.5 keV energy point varies as shown in the accompanying Figure 9 The response peak is 6.37×10 -7 sr.

[0075] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments according to the needs after reading the specification, and the modifications are not creative contributions, but are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A variable working point grazing incidence X-ray microscopy optical structure, characterized by: The application relates to a three-mirror X-ray imaging system, which comprises an object point (1), a first mirror (2), a second mirror (3), a third mirror (4) and an image plane (5); the object point (1) is located in front of the first mirror (2), and the image plane (5) is located behind the third mirror (4); the first mirror (2), the second mirror (3) and the third mirror (4) are arranged in series and work under the condition of a small grazing incidence angle; the first mirror (2) and the second mirror (3) constitute a double-mirror structure for high-resolution imaging, and the third mirror (4) for adjusting a working energy point is arranged in the light path at the rear end of the second mirror (3); A rectangular coordinate system is established with the object point (1) as the origin, the object point (1) points to the image plane (5) as the positive direction of the X axis, and the object point (1) vertically upwards is the positive direction of the Z axis; the placement position of the third mirror (4) in the light path is (D_x, D_z), and the calculation formula of the vertical coordinate D_z of the third mirror (4) in the light path is as follows: Wherein, M is the system magnification, u is the distance from the object point (1) to the center of the first mirror (2), D_x is the horizontal coordinate of the center of the third mirror (4), C_x is the horizontal coordinate of the center of the second mirror (3), and theta1 is the grazing incidence angle of the first mirror (2); The calculation formula of the grazing incidence working angle theta3 of the third mirror (4) is as follows: where θ1 is the grazing incidence angle of the first mirror (2), M is the magnification of the system, and θ axis_3 is the angle between the third mirror (4) and the central axis. The grazing incidence working angle of the third mirror (4) is adjusted to realize continuous adjustment of the system working energy point, and the formula is as follows: Wherein, E is the working energy point of the system, d is the period thickness of the X-ray period multilayer film, theta3 is the grazing incidence angle of the third mirror (4), and delta is an angle correction small amount; The vertical axis distance of the image point generated after three reflections in the image plane (5) from the central axis is calculated, and the calculation formula is as follows: E_z=tan2theta3[(M+1)u-D_x] (4) Wherein, E_z is the vertical axis distance of the image point in the image plane (5) from the central axis, theta3 is the grazing incidence angle of the third mirror (4), M is the system magnification, u is the distance from the object point (1) to the center of the first mirror (2), and D_x is the distance from the object point (1) to the center of the third mirror (4); The system response efficiency considers the optical configuration geometric collection solid angle and the efficiency of three grazing incidence reflections, and the calculation formula of the system response efficiency of the optical structure is as follows: Wherein, wherein w is the effective mirror width; theta1 is the grazing incidence angle of the first mirror (2); L1 is the mirror length of the first mirror (2); eta1, eta2 and eta3 are the reflectivities of the first mirror (2), the second mirror (3) and the third mirror (4) respectively; and u is the distance from the object point (1) to the center of the first mirror (2).

2. A variable working point grazing incidence X-ray microscopy optical structure according to claim 1, characterized in that: The surface types of the first mirror (2) and the second mirror (3) are spherical-spherical, cylindrical-cylindrical, super-torus-spherical, hyperbolic-cylindrical or rotating hyperboloid-rotating ellipsoid.

3. A variable working point grazing incidence X-ray microscopy optical structure according to claim 1, characterized in that: The surfaces of the first mirror (2) and the second mirror (3) are coated with a wide-spectrum response reflective film.

4. The variable working point grazing incidence X-ray microscopy optical structure of claim 1, wherein: The third mirror (4) is a plane mirror, and a X-ray periodic multilayer film with a specific periodic thickness is coated on the surface of the third mirror (4) to realize narrow spectrum response.

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