A collimator for high-energy x-ray detection

Abstract

The application discloses a collimator for high-energy X-ray detection, comprising a plurality of detachably connected monomers, each of the monomers comprising: a collimator frame, the collimator frame comprising a barrel with two open ends and a plurality of grid plates, the plurality of grid plates being arranged in the barrel, the plurality of grid plates being arranged in parallel and spaced apart from each other, the plate surface of the grid plate being parallel to the axis of the barrel; and a tantalum plate, the surface of the tantalum plate being tantalum, a plurality of the tantalum plates being detachably connected between two adjacent grid plates and between the grid plate and the inner wall of the barrel.

Description

Technical Field

[0001] This application relates to the field of collimator technology, and more particularly to a collimator for high-energy X-ray detection. Background Technology

[0002] The Einstein Probe (EP) satellite is an astronomical exploration satellite designed for future time-domain astronomy and high-energy astrophysics. The EP satellite's payload includes a large-field-of-view soft X-ray monitor and an X-ray telescope (FXT). The FXT telescope is used for first-time depth follow-up observations of transient sources detected by the monitor and for observing opportunistic targets detected by other instruments. To observe target X-ray sources, the FXT telescope employs a traditional nested grazing incidence focusing telescope configuration, with a PNCCD serving as the focal plane detector for X-ray photon readout. The FXT's focusing lens consists of 54 nested mirrors, achieving focusing through two reflections: a parabolic surface and a hyperboloid.

[0003] However, existing collimators are not only expensive to manufacture, but also heavy, which greatly increases the burden of use. Summary of the Invention

[0004] This specification presents an embodiment of a collimator for high-energy X-ray detection, which solves the problems of high cost and heavy weight of existing collimators.

[0005] Therefore, the embodiments of this specification provide the following solution: a collimator for high-energy X-ray detection, comprising a plurality of detachably connected units, each unit comprising:

[0006] A collimator frame, comprising a cylindrical body open at both ends and a plurality of grid plates, wherein the plurality of grid plates are disposed within the cylindrical body, the plurality of grid plates are parallel to each other and spaced apart, and the surface of the grid plates is parallel to the axis of the cylindrical body;

[0007] A tantalum plate, the surface of which is tantalum, and several tantalum plates can be detachably connected between two adjacent grid plates and between the grid plates and the inner wall of the cylinder.

[0008] Furthermore, several of the grid plates are integrally formed with the cylinder.

[0009] Furthermore, the collimator frame is cut from aluminum alloy material.

[0010] Furthermore, the aforementioned grid plates are arranged at equal intervals.

[0011] Furthermore, the inner wall of the cylinder and the surface of the grid plate are provided with an X-ray shielding layer.

[0012] Furthermore,

[0013] Each of the grid plates has a plurality of slots on both sides and on the inner wall of the cylinder, and the plurality of slots on both sides of each grid plate are staggered.

[0014] The slot is arranged along the axial direction of the cylinder;

[0015] The slots on the opposite surfaces of two adjacent grid plates correspond;

[0016] The slots on the inner wall of the cylinder correspond to the slots on the grid plate;

[0017] The tantalum plate can be fixed between two adjacent grid plates and between the grid plate and the inner wall of the cylinder through the slot, so that the inside of the cylinder has a grid structure.

[0018] Furthermore, the collimator frame also includes a flange disposed at the end.

[0019] Furthermore, the collimator frame is made of LY12CZ aluminum alloy.

[0020] Furthermore, the tantalum plate has a thickness of 0.15 mm.

[0021] Furthermore, the thickness of the grid plate is 2 mm.

[0022] The above-mentioned technical solutions adopted in the embodiments of this application can achieve the following beneficial effects: with the support of an aluminum alloy frame, it is easy to ensure the parallelism between the tantalum plates and their parallelism with the outer cylindrical surface of the collimator unit; the collimator unit has high mechanical strength, which can easily meet the requirements of dynamic environment test and thermal cycling test; the collimator unit has low cost; and the unit has great strength and overall shielding capability, which can replace some parts of the telescope, such as the assembly aluminum barrel, lead scintillation crystal shielding ring, etc., so as to further reduce the weight of the telescope. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0025] In the attached diagram:

[0026] Figure 1 This is a cross-sectional structural schematic diagram of a single collimator for high-energy X-ray detection provided as an embodiment of the specification. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0029] This embodiment provides a collimator for high-energy X-ray detection. Please refer to [link to documentation]. Figure 1 As shown, the system includes several detachably connected units. Each collimator unit is, but is not limited to, cylindrical, with a height of 300 mm, an inner diameter of φ188 mm, and an outer diameter (assembly surface) of φ205–206 mm. Each unit includes a collimator frame and a tantalum plate.

[0030] In one possible implementation, the collimator frame includes a cylindrical body 1 with openings at both ends and a plurality of grid plates 2. The grid plates are disposed inside the cylindrical body, and are arranged parallel to each other and spaced apart. The surface of the grid plates is parallel to the axis of the cylindrical body. The tantalum plate 3 is made of tantalum or is made entirely of tantalum material or is coated with tantalum material. The plurality of tantalum plates can be detachably connected between adjacent grid plates and between the grid plates and the inner wall of the cylindrical body.

[0031] Specifically, the plurality of grid plates are integrally formed with the cylinder. The collimator frame is cut from aluminum alloy. The plurality of grid plates are arranged at equal intervals. An X-ray shielding layer is provided on the inner wall of the cylinder and the surface of the grid plates. Each grid plate has a plurality of slots 21 on both sides and on the inner wall of the cylinder, and the plurality of slots on both sides of each grid plate are staggered; the slots are arranged along the axial direction of the cylinder; the slots on the opposite sides of two adjacent grid plates correspond to each other; the slots on the inner wall of the cylinder correspond to the slots on the grid plates; the tantalum plate can be fixed between two adjacent grid plates and between the grid plates and the inner wall of the cylinder through the slots, so that the interior of the cylinder has a plurality of grid structures. The unit is composed of numerous 30mm×6mm grids, forming a field of view of 1.1°×5.7°, which ensures both high imaging resolution (modulation effect in the 1.1° direction) and wide field of view (5.7° direction). The non-parallelism of the internal grid plates is less than 1′ (0.087mm / 300mm), with a high duty cycle, low weight, and good mechanical strength and temperature stability. The collimator frame also includes a flange 4 located at the end. The collimator frame is made of LY12CZ aluminum alloy. The tantalum plate is 0.15mm thick. The grid plate is 2mm thick.

[0032] The collimator frame is made of LY12CZ aluminum alloy. Because LY12CZ aluminum alloy is much stronger than lead-antimony alloy, five grid plates are provided to increase the duty cycle. The grid plate thickness is 2mm, without bosses, and the slot depth is 1mm. To allow for the cutting of 1mm deep slots and the insertion of thin tantalum plates, the slots on both sides of the main grid plate are staggered. For gamma photons from the lateral surface, the outer ring collimator unit itself constitutes the shielding of the inner ring unit; therefore, the shielding cylinder under each unit can be removed, replaced by a large shielding cylinder surrounding the inner and outer rings of the entire collimator assembly. The unit has high strength and overall shielding capability, further reducing the overall weight during use. The shielding layer covering the inner wall of the cylinder and the grid plates includes, but is not limited to, 0.15mm thick tantalum, weighing 1.635kg. The collimator unit weighs 10.452kg, a reduction of 9.174kg compared to the unit weight using the lead-antimony alloy scheme, further reducing the overall weight.

[0033] To further explain, for the first time, a 1.1°×5.7° field of view is achieved using thin tantalum sheets with a height of 300mm. The collimation hole height is 300mm, and the thickness of the tantalum sheet between the 6mm×30mm collimator holes is only 0.15mm. There are a total of 158 collimation channels with a duty cycle as high as 88.6%.

[0034] Using aluminum alloy as the structural frame and bonding tantalum sheets reduces the weight by more than 50%, saving weight resources for the satellite platform.

[0035] The physical function of a collimator is to allow X-rays from a specific direction to pass through while absorbing and attenuating X-rays from other directions. Materials that can meet the requirements for shielding high-energy X-rays include lead (Pb), tungsten (W), tantalum (Ta), etc., as shown in Table 1.

[0036] Table 1. Attenuation coefficients of common collimator materials (140keV photons)

[0037]

[0038] Quoted from National Institute of Standards and Technology XCOM: PhotonCrossSectionDatabase (Gaithersburg, MD) http: / / physics.nist.gov / xcom.

[0039] Based on the linear attenuation coefficients and collimation aperture height / width ratios of the aforementioned materials in the high-energy X-ray region (20–250 keV), a thickness of 0.15 mm to 0.20 mm is sufficient to meet the shielding requirements. Lead has the lowest density-to-linear attenuation coefficient ratio, meaning it requires the least mass to achieve the same linear attenuation coefficient.

[0040] In addition to meeting the physical requirements of the telescope, the selection of materials must take into account the weight and strength of the collimator (whether it can withstand the acceleration and vibration during the launch process), the feasibility of the manufacturing process, and the material and processing costs.

[0041] Pure lead has a melting point of 327℃ and poor mechanical properties. Tantalum has a melting point of 2996℃, good plasticity at room temperature, and can be processed into foils less than 10μm thick without intermediate annealing. Tungsten has high strength and elastic modulus, but is brittle and hard, making it difficult to press into sheets less than 0.3mm thick. It suffers from severe low-temperature embrittlement and high-temperature oxidation, and has an extremely high melting point (3410℃), making it difficult to process.

[0042] Tantalum plates are priced between ¥4,000 and ¥9,000 per kg. Tungsten plates (0.2 mm thick) are priced at ¥4,900 per kg. Lead is priced at only around ¥8 per kg. Gold (Au), platinum (Pt), and uranium (U) are rare and precious metals.

[0043] Considering physical properties, mechanical properties, material costs, and processing difficulty, lead and tantalum are the preferred materials for collimators. Lead and tantalum are heavy metals with very high density, and a collimator unit made entirely of them would inevitably be very heavy. Since 0.15mm to 0.20mm thick lead and tantalum alloys can meet the physical requirements, using lightweight structural materials can significantly reduce the weight of the unit. LY12CZ high-strength aluminum alloy (LY indicates hard aluminum alloy; C indicates quenching; Z indicates natural aging) has advantages such as low density, high mechanical properties, low processing cost, and good corrosion resistance (see Tables 2-5), and is a commonly used material in aerospace. Using LY12CZ to manufacture the structural frame and lead or tantalum thin plates as the physical functional materials is the optimal combination to achieve the overall technical specifications of the collimator unit. As shown in Tables 2-6, lead and aluminum alloys have the closest coefficients of thermal expansion, and their combination is less prone to thermal stress.

[0044] Table 2 Chemical composition of LY12CZ hard aluminum alloy (BG3190-82)

[0045] Cu Mg Mn Fe Si Zn Ni Ti 3.8-4.9 1.2-1.8 0.3-0.9 0.5 0.5 0.3 0.1 0.15

[0046] Quoted from "Mechanical Design Handbook", Volume 1, pp. 3-258.

[0047] Table 3 Density of materials (g / cm³) 3 )

[0048] Material Pb Sb Al Ta Pb-Sb alloy LY12CZ aluminum alloy D 11.34 6.67 2.7 16.6 <![CDATA[10.86 * ]]> 2.78

[0049] Excerpted from "Mechanical Design Handbook", * indicates measured value.

[0050] Table 4 Thermophysical properties of LY12 hard aluminum alloy

[0051] Material category and model <![CDATA[Tensile strength σ b (Mpa)]]> <![CDATA[σ 0.2 (Mpa)]]> δ(%) LY12CZ hot extruded tube 430 280 10.0

[0052] Excerpted from "Mechanical Design Handbook", Volume 1, pp. 3-321

[0053] Table 5 Mechanical properties of LY12CZ hard aluminum alloy hot extruded tubes (GB3191-82)

[0054]

[0055] Table 6. Average linear expansion coefficient of relevant materials from 0 to 100℃ (×10) -6 / ℃)

[0056] Material Pb Sb Al Ta Pb-Sb alloy LY12CZ aluminum alloy <![CDATA[α L ]]> 28.3 10.8 23.8 6.75 <![CDATA[23.11 * ]]> <![CDATA[22~24 # ]]>

[0057] Referenced from <Physical Properties of Materials>, # referenced from <Mechanical Design Handbook> αL (20~100℃), * is the measured value.

[0058] If LY12CZ high-strength hard aluminum alloy is used as the collimator frame, with an internally cast lead-antimony alloy cylinder and five grid plates, and 0.2mm wide slots cut into the grid plates to insert 156 0.15mm thick tantalum plates, this constitutes a single collimator unit. A unit with 2mm thick grid plates weighs 19.6kg, and after thinning all five grid plates to 1.2mm, the unit weight is 16.3kg.

[0059] Even if lead-antimony alloy is used instead of lead, the mechanical strength is still very low. A thickness of 1.2mm for the inner barrel and main grid plate is already the limit to meet the processing and mechanical environment requirements, while 0.15-0.20mm is sufficient for physical requirements. In the weight of the collimator unit, the lead-antimony alloy inner barrel and main grid plate account for 65%. To further reduce the weight of the unit, the amount of lead-antimony alloy used must be reduced.

[0060] Therefore, by adopting the technical solution of this application, the collimator unit weighs 10.452 kg, with a tantalum covering the inner wall of the aluminum alloy cylinder and the grid shielding layer being 0.15 mm thick. This is 9.174 kg less than the unit weight using the lead-antimony alloy solution, which greatly reduces the weight of the unit.

[0061] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0062] It should also be noted that the terms "first" and "second" in this application are used to distinguish multiple objects with the same name, and are not used to limit the order or size. Unless otherwise specified, they have no other special meaning.

[0063] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A collimator for high-energy X-ray detection, characterized in that Each of the monomers comprises: A collimator frame comprising a cylinder open at both ends and a plurality of grids, the plurality of grids being arranged in the cylinder, the plurality of grids being parallel to each other and spaced apart, the plate surface of the grid being parallel to the axis of the cylinder; A tantalum plate, the surface of the tantalum plate being tantalum, a plurality of tantalum plates being detachably connected between two adjacent grids and between the grid and the inner wall of the cylinder; Each of the two surfaces of the grid and the inner wall of the cylinder is provided with a plurality of insertion slots, the plurality of insertion slots on the two surfaces of each of the grid being staggered; The insertion slots are arranged along the axis of the cylinder, the insertion slots on the opposite surfaces of two adjacent grids correspond to each other; The insertion slots on the inner wall of the cylinder correspond to the insertion slots on the grid; the tantalum plate can be fixed between two adjacent grids and between the grid and the inner wall of the cylinder through the insertion slots, so that the inside of the cylinder presents a plurality of grid structures; The thickness of the tantalum plate is 0.15 mm, and the thickness of the grid is 2 mm.

2. A collimator for high-energy X-ray detection as claimed in claim 1, characterized in that The plurality of grids and the cylinder are in an integrated structure.

3. A collimator for high-energy X-ray detection according to claim 2, characterized in that The collimator frame is cut from an aluminum alloy material.

4. A collimator for high-energy X-ray detection according to claim 1, characterized in that The plurality of grids are arranged at equal intervals.

5. A collimator for high-energy X-ray detection as defined in claim 1, characterized in that The inner wall of the cylinder and the surface of the grid are provided with an X-ray shielding layer.

6. A collimator for high-energy X-ray detection as defined in claim 1, characterized in that The collimator frame further comprises a flange plate arranged at the end.

7. A collimator for high-energy X-ray detection as defined in claim 1, characterized in that The collimator frame adopts LY12CZ aluminum alloy.

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