Micro-focus X-ray tube

Abstract

The invention provides a micro-focus X-ray tube. An exit port of an electron acceleration structure in a vacuum cavity is hermetically communicated with an entrance port of a first drift tube; an incident port of a drift channel penetrating through the pole shoe magnetic lens structure is hermetically communicated with an emergent port of the first drift tube, an emergent port of the drift channel is hermetically communicated with an incident port of the second drift tube, the second drift tube sequentially penetrates through magnet yoke central shafts of the quadrupole magnetic lenses, and an emergent port of the second drift tube is hermetically connected with the transmission target. The pole shoe magnetic lens and the quadrupole magnetic lens are combined into the micro-focus X-ray tube, so that the focusing size of an electron beam is further reduced, and high-resolution imaging and accurate control of the size of the electron beam are realized; meanwhile, the focusing effect of the electron beam is improved by arranging the materials of the pole shoe and the magnet yoke, and the resolution of the X-ray source is further improved; in addition, a multi-stage quadrupole magnetic lens and a plurality of groups of single-pole shoe magnetic lenses are arranged, so that the focusing precision of the electron beam and the focusing effect regulation and control capability are further improved.

Description

Technical Field

[0001] This invention belongs to the field of X-ray tube technology, and in particular relates to a microfocus X-ray tube. Background Technology

[0002] The most common focusing methods for microfocus X-ray tubes are electrostatic focusing and electromagnetic focusing. Electrostatic focusing creates a specific electrostatic field distribution by applying appropriate voltages to specially constructed cathode and anode electrode structures, thereby guiding the electron beam to focus. Electromagnetic focusing, on the other hand, utilizes a magnetic field to generate a Lorentz force on moving electrons, causing the electron beam to deflect and converge under the influence of the magnetic field.

[0003] Electrostatic focusing has relatively low focusing accuracy because it is difficult to achieve a perfectly uniform distribution of the electrostatic field. It is also sensitive to the initial energy and divergence angle of charged particles and is easily affected by the space charge effect, leading to a decrease in the quality of the focused beam. Electromagnetic focusing, on the other hand, typically uses an electromagnetic coil placed outside the X-ray tube. When energized, it generates a magnetic field whose direction and strength can be adjusted as needed. This results in higher focusing accuracy, as the magnetic field can more precisely control the trajectory of electrons, achieving a smaller beam spot size and higher resolution. It also results in fewer aberrations and more stable and precise control of the electron beam, giving it stronger focusing capabilities. It can effectively focus the electron beam onto a small area, achieving higher electron beam density and thus increasing X-ray intensity.

[0004] However, with the rapid development of semiconductor technology, the defect size of wafers and chips is getting smaller and smaller. Traditional detection methods are difficult to meet the high precision requirements. X-ray microfocus detection technology is needed to provide high-resolution imaging with smaller focal size to detect micron- or even submicron-sized defects, such as cracks, voids and material inhomogeneities. However, the microfocus X-ray tubes in the current technology still cannot meet the higher precision detection requirements in the current smaller size process.

[0005] Therefore, there is an urgent need for a structure that can further improve the electron beam focusing capability of X-ray tubes.

[0006] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating the understanding of those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because these solutions have been described in the background section of this application. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a microfocus X-ray tube to solve the problem that the electron beam focusing capability of X-ray tubes in the prior art is difficult to further improve.

[0008] To achieve the above and other related objectives, the present invention provides the following technical solutions:

[0009] The present invention provides a microfocus X-ray tube, the microfocus X-ray tube comprising: a vacuum cavity, an electron acceleration structure, a first drift tube, a collimation structure, a pole piece magnetic lens structure, a quadrupole magnetic lens structure, a second drift tube, and a transmission target;

[0010] The vacuum chamber is provided with the electron acceleration structure, the outlet of the electron acceleration structure is sealed and connected to the inlet of the first drift tube, and the collimation structure is provided in the first drift tube near the outlet of the electron acceleration structure.

[0011] The pole shoe magnetic lens structure includes at least one set of single pole shoe magnetic lenses. A drift channel is provided through the pole shoe magnetic lens structure, and the drift channel passes through the central through hole of each single pole shoe magnetic lens. The inlet of the drift channel is sealed and connected to the outlet of the first drift tube, and the outlet of the drift channel is sealed and connected to the inlet of the second drift tube.

[0012] The quadrupole magnetic lens structure includes at least one quadrupole magnetic lens group, and each quadrupole magnetic lens group includes two quadrupole magnetic lenses with orthogonal focusing directions. The second drift tube passes through the magnetic yoke central axis of each quadrupole magnetic lens in sequence.

[0013] The outlet of the second drift tube is sealed to the transmission target.

[0014] Optionally, the electron acceleration structure includes a high-voltage socket, a cathode, a gate, and an anode. The high-voltage socket is electrically connected to the cathode to provide a negative high voltage, and the anode is grounded. The gate is located between the cathode and the anode, close to the cathode. The anode is at a predetermined distance from the gate and the cathode as an acceleration region, and the exit port of the electron acceleration structure is located on the anode.

[0015] Optionally, the collimation structure is a deflection coil, which surrounds the first drift tube near the exit port of the electron acceleration structure.

[0016] Optionally, each set of the single pole shoe magnetic lenses includes a lower pole shoe, an upper pole shoe, and a focusing magnetic lens, wherein the lower pole shoe is located near the first drift tube;

[0017] The lower pole shoe is a first sleeve including a first top cover and a first opening, and the upper pole shoe is a second sleeve including a second top cover and a second opening, wherein the first opening and the second opening are fitted and fixed together; the first top cover includes a first plate surface, and the first plate surface has an injection hole corresponding to the drift channel.

[0018] The second top cover includes a second plate and a frustum portion, and the drift channel passes through the center of the second plate and the frustum portion; the first bottom surface of the frustum portion is fixedly connected to the second plate, and there is a predetermined distance between the second bottom surface of the frustum portion and the first plate to form a gap, and the area of ​​the first bottom surface of the frustum portion is larger than the area of ​​the second bottom surface; there are two symmetrical hollow regions between the frustum portion and the second sleeve, and a focusing magnetic lens is provided in each hollow region; the focusing magnetic lens includes a focusing coil and a coil frame, and the focusing coil surrounds the coil frame and is fixedly connected to the upper pole shoe.

[0019] Optionally, the upper and lower pole shoes are made of pure iron or electrical pure iron DT4C, the coil frame is made of aluminum alloy, and the focusing coil is made of enameled copper wire.

[0020] Optionally, the preset distance between the second bottom surface of the frustum portion of the upper pole shoe and the first plate surface is 3 mm to 6 mm.

[0021] Optionally, each of the quadrupole magnetic lenses includes one yoke and four sets of quadrupole magnetic coils, the central axis of each yoke being coincident with the central axis of the drift channel; each yoke includes four yoke protrusions, the four yoke protrusions of each yoke being arranged sequentially around the central axis of the yoke and facing the central axis, the included angle between two adjacent yoke protrusions of each yoke being 90°; each yoke protrusion is wound by one set of quadrupole magnetic coils, such that the magnetic poles of any two adjacent yoke protrusions are opposite; the second drift tube sequentially passes through the central axis of each yoke, and each yoke is fixed to the outer wall of the second drift tube.

[0022] Optionally, the yoke in the quadrupole magnetic lens is provided with a coolant fluid channel.

[0023] Optionally, the yoke is made of soft iron, soft magnetic alloy, or cold-rolled silicon steel sheet.

[0024] Optionally, the exit port of the electron acceleration structure and the inlet port of the first drift tube are sealed together by a rubber ring; the inlet port of the drift channel is connected to the exit port of the first drift tube by a rubber ring; the exit port of the drift channel is connected to the inlet port of the second drift tube by a sealed connection; and the exit port of the second drift tube is connected to the transmission target by a rubber ring.

[0025] As described above, the microfocus X-ray tube of the present invention has the following beneficial effects:

[0026] This invention combines a pole piece magnetic lens and a quadrupole magnetic lens structure in a microfocus X-ray tube to perform two-step focusing of the electron beam. This allows the electron beam to be focused to a very small size, achieving high-resolution imaging and precise electron beam size control, thus meeting the development needs of higher spatial resolution for microfocus X-ray sources.

[0027] By adjusting the materials of the pole shoes and magnetic yoke, this invention can further improve the focusing effect on the electron beam and further improve the spatial resolution of the X-ray source.

[0028] This invention, by setting up multiple levels of quadrupole magnetic lenses and / or multiple sets of unipolar shoe lenses, can further improve the focusing accuracy of the electron beam and the ability to control the focusing effect.

[0029] The present invention, in conjunction with the coolant fluid channel provided on the magnetic yoke, can achieve a higher heat dissipation effect to meet the application requirements of X-ray tubes. Attached Figure Description

[0030] Figure 1 The image shown is a front perspective view of the microfocus X-ray tube of this invention.

[0031] Figure 2 The image shown is a front perspective view of the monopolar shoe lens of the microfocus X-ray tube in this invention.

[0032] Figure 3 The diagram shown is a top perspective view of the monopole shoe lens of the microfocus X-ray tube in this invention.

[0033] Component designation explanation

[0034] 1. Cathode; 2. Grid; 3. Anode; 4. Deflection coil; 5. Unipolar shoe lens; 6. Quadrupole lens; 7. Transmission target; 8. Vacuum cavity; 9. High-voltage socket;

[0035] 41. First drift tube;

[0036] 51. Lower pole shoe; 511. First top cover; 512. First sleeve; 52. Upper pole shoe; 521. Second plate; 522. Frustum section; 523. Gap; 524. Second sleeve; 53. Focusing magnetic lens; 531. Focusing coil; 532. Coil frame; 54. Drift channel;

[0037] 61. First quadrupole magnetic lens; 62. Second quadrupole magnetic lens; 63. Magnetic yoke; 631. Magnetic yoke protrusion; 632. Recessed structure; 633. Ring frame; 634. Quadrupole magnetic coil; 65. Second drift tube. Detailed Implementation

[0038] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0039] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged and not to scale. Furthermore, these schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0040] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the accompanying drawings for devices in use or operation.

[0041] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0042] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0043] Currently, microfocus X-ray tubes using electromagnetic focusing typically employ monopole shoe or bipole shoe focusing structures, utilizing the non-uniform magnetic field generated by the poles to focus a charged particle beam. The principle is that when a charged particle enters a magnetic field, it experiences a magnetic force, causing its trajectory to bend towards the axis. The poles, through their structure and optimized magnetic field distribution, effectively guide and constrain the magnetic field, enabling the electron beam to be focused within it, thereby improving the equipment's performance and accuracy. However, this method has a relatively weak focusing effect, and the generated magnetic field distribution is relatively simple. The focusing effect on the particle beam depends to some extent on the initial velocity and position of the particles. Therefore, it is only suitable for applications with low focusing accuracy requirements and cannot meet the increasingly high demands for electron beam focusing precision.

[0044] Quadrupole magnetic lenses are primarily used in particle accelerators and electron microscopes to focus and control charged particle beams. They achieve focusing and divergence of charged particles through a non-uniform magnetic field distribution and are widely applied in nuclear and particle physics research. However, due to the complex magnetic field distribution of quadrupole magnetic lenses, it is generally difficult to directly achieve precise focusing of electron beams; furthermore, the complex structure of quadrupole magnetic lenses makes them incompatible with the compact design of microfocus X-ray tubes; additionally, quadrupole magnetic lenses typically require high magnetic field strength, leading to significant heat generation, while the cooling systems of microfocus X-ray tubes are generally simpler. Therefore, microfocus X-ray tubes typically employ simpler and more efficient electrostatic or electromagnetic focusing methods and are not used in the field of microfocus X-rays.

[0045] A quadrupole magnetic lens focusing structure consists of four magnetic poles with opposite polarities for adjacent poles. The magnetic field generated by the quadrupole magnetic lens has different gradients in different directions, causing the charged particle beam to converge in one direction and diverge in the direction orthogonal to it. By combining multiple quadrupole magnetic lenses in a reasonable way, it is possible to focus the particle beam in two orthogonal directions. It has strong focusing ability and can achieve high-precision focusing of the particle beam. Due to its special magnetic field distribution, it can independently control the particle beam in two directions, thus better meeting the focusing requirements of different applications.

[0046] like Figure 1 As shown, the present invention provides a microfocus X-ray tube, which includes: a vacuum cavity 8, an electron acceleration structure, a first drift tube 41, a collimation structure, a pole piece magnetic lens structure, a quadrupole magnetic lens structure, a second drift tube 65, and a transmission target 7.

[0047] The vacuum cavity 8 is provided with the electron acceleration structure, the outlet of the electron acceleration structure is sealed and connected to the inlet of the first drift tube 41, and the collimation structure is provided in the first drift tube 41 near the outlet of the electron acceleration structure.

[0048] The pole shoe magnetic lens structure includes at least one set of single pole shoe magnetic lenses 5. A drift channel 54 is provided through the pole shoe magnetic lens structure. The drift channel 54 passes through the central through hole of each single pole shoe magnetic lens 5. The inlet of the drift channel 54 is sealed and connected to the outlet of the first drift tube 41. The outlet of the drift channel 54 is sealed and connected to the inlet of the second drift tube 65.

[0049] The quadrupole magnetic lens structure includes at least one quadrupole magnetic lens group, and each quadrupole magnetic lens group includes two quadrupole magnetic lenses 6 with orthogonal focusing directions. The second drift tube 65 passes through the central axis of the magnetic yoke 63 of each quadrupole magnetic lens 6 in sequence.

[0050] The outlet of the second drift tube 65 is sealed to the transmission target 7.

[0051] This invention utilizes a quadrupole magnetic lens structure, which was previously considered unsuitable for microfocus X-ray tubes, in combination with a pole piece magnetic lens for two-step focusing of the electron beam. This allows the electron beam to be focused to a very small size, reducing it from 2.5 micrometers in existing technologies to the submicrometer level of less than 1 micrometer. Furthermore, since both the pole piece magnetic lens and the quadrupole magnetic lens structure can be adjusted individually by changing the current that generates the magnetic field, the flexibility and precision of focusing size adjustment are improved. This enables high-resolution imaging and precise electron beam size control, meeting the development needs of microfocus X-ray sources for higher spatial resolution.

[0052] In one embodiment, two or more sets of monopole magnetic shoe lenses 5 are provided, and they are sealed to each other through a sealed connection between the drift channels 54 of each monopole magnetic shoe lens 5.

[0053] This invention, by setting up multiple sets of monopole magnetic shoe lenses 5 in a sealed connection, can provide stronger focusing capability, making the electron beam focusing more precise, thereby improving the resolution and imaging quality of the X-ray tube. At the same time, through the synergistic effect of multiple sets of monopole magnetic shoe lenses 5, the stability and uniformity of the magnetic field can be enhanced, reducing magnetic field fluctuations and interference, and improving the stability of the electron beam. In addition, the combination of multiple sets of monopole magnetic shoe lenses 5 can optimize the distribution of the magnetic field, making the magnetic field more concentrated and uniform, thereby improving the focusing effect and stability of the electron beam.

[0054] In one embodiment, two or more quadrupole magnetic lens groups are provided, and they are sealed to each other through a sealing connection between the second drift tubes 65 of each quadrupole magnetic lens group.

[0055] This invention, through the sealed connection of multiple quadrupole magnetic lens groups, enables precise control of the electron beam in different directions, improving the focusing accuracy and directionality of the electron beam, thereby enhancing the imaging quality of the X-ray tube. Simultaneously, by adjusting the magnetic field strength and direction of each magnetic lens group, dynamic adjustment of the electron beam can be achieved to adapt to different detection requirements and operating conditions. Furthermore, the combination of multiple quadrupole magnetic lens groups optimizes the magnetic field distribution, making the magnetic field more uniform and stable, thereby improving the focusing effect and stability of the electron beam.

[0056] In one embodiment, any two adjacent magnetic yoke protrusions 631 within a quadrupole magnetic lens structure consisting of two or more quadrupole magnetic lens groups have opposite magnetic properties, thereby achieving the minimum focusing size for the electron beam.

[0057] In one embodiment, the vacuum chamber 8 is a pre-vacuum-set closed vacuum chamber 8.

[0058] In one embodiment, the vacuum chamber 8 is an open vacuum chamber 8 that is connected to a vacuum pump for vacuuming operations to maintain a vacuum state.

[0059] In one embodiment, such as Figure 1 As shown, the electron acceleration structure includes a high-voltage socket 9, a cathode 1, a grid 2, and an anode 3. The high-voltage socket 9 is electrically connected to the cathode 1 to provide a negative high voltage, and the anode 3 is grounded. The grid 2 is located between the cathode 1 and the anode 3, close to the cathode 1. The anode 3 is at a preset distance from the grid 2 and the cathode 1 as an acceleration region. The exit port of the electron acceleration structure is located on the anode 3.

[0060] In one embodiment, the anode 3 can also be connected to a positive high voltage. Specifically, the appropriate option can be selected based on actual needs, all within the scope of this utility model.

[0061] In one embodiment, such as Figure 1 As shown, the collimation structure is a deflection coil 4, which surrounds the first drift tube 41 near the exit port of the electron acceleration structure.

[0062] This invention uses a deflection coil 4 to generate a magnetic field that acts on the electron beam accelerated from the anode 3, thereby changing the path of the electron beam and allowing the focal position of the electron beam to be precisely adjusted to correct the deviation of the focal position.

[0063] In one embodiment, such as Figure 2 As shown, each set of the single pole shoe magnetic lens 5 includes a lower pole shoe 51, an upper pole shoe 52 and a focusing magnetic lens 53, wherein the lower pole shoe 51 is located near the first drift tube 41;

[0064] The lower pole shoe 51 is a first sleeve 512 including a first top cover 511 and a first opening, and the upper pole shoe 52 is a second sleeve 524 including a second top cover and a second opening, with the first opening and the second opening being fixed together; the first top cover 511 includes a first plate surface, and the first plate surface has an injection hole corresponding to the drift channel 54.

[0065] The second top cover includes a second plate surface 521 and a frustum portion 522. The drift channel 54 passes through the center of the second plate surface 521 and the frustum portion 522. The first bottom surface of the frustum portion 522 is fixedly connected to the second plate surface 521. A predetermined distance exists between the second bottom surface of the frustum portion 522 and the first plate surface to form a gap 523. The area of ​​the first bottom surface of the frustum portion 522 is larger than the area of ​​the second bottom surface. There are two symmetrical hollow regions between the frustum portion 522 and the second sleeve 524. A focusing magnetic lens 53 is provided in each hollow region. The focusing magnetic lens 53 includes a focusing coil 531 and a coil frame 532. The focusing coil 531 surrounds the coil frame 532 and is fixedly connected to the upper pole shoe 52.

[0066] The present invention utilizes the gap 523 formed between the frustum portion 522 of the upper pole shoe 52 and the first plate surface of the lower pole shoe 51 at the position of the incident electron beam near the first drift tube 41 in the single pole shoe magnetic lens 5 to compress the magnetic field of the pole shoe, increase the magnetic field strength at the incident position of the electron beam, and make the magnetic field distribution more uniform, thereby greatly improving the focusing ability of the electron beam and further reducing the focusing size of the electron beam.

[0067] In one embodiment, the first opening of the lower pole shoe 51 and the second opening of the upper pole shoe 52 are fixed together by bolts.

[0068] In one embodiment, the focusing coil 531 is fixed to the upper pole shoe 52 by screws.

[0069] In one embodiment, the first top cover 511 and the first sleeve 512 are an integral structure, the second top cover and the second sleeve 524 are an integral structure, and the second plate 521 and the frustum portion 522 are an integral structure.

[0070] In one embodiment, the upper pole shoe 52 and the lower pole shoe 51 are made of pure iron or electrical pure iron DT4C, the coil frame 532 is made of aluminum alloy, and the focusing coil 531 is made of enameled copper wire.

[0071] This invention utilizes pure iron or electrical pure iron DT4C with high magnetic permeability as the material for the pole shoes, which can effectively guide and constrain the magnetic field distribution, making the magnetic field more concentrated and uniform, thereby improving the focusing performance and stability of the electron beam. The coil frame 532 is made of aluminum alloy with good thermal conductivity, which helps dissipate heat. At the same time, its lightweight characteristics can reduce the weight of the microfocus X-ray tube, improving the portability and ease of installation of the microfocus X-ray tube. The focusing coil 531 is made of enameled copper wire with good conductivity and mechanical strength, which can effectively conduct current and generate a magnetic field, while ensuring the stability and durability of the coil.

[0072] In one embodiment, the preset distance between the second bottom surface of the frustum portion 522 of the upper pole shoe 52 and the first plate surface is 3 mm to 6 mm.

[0073] In one embodiment, the preset distance between the second bottom surface of the frustum portion 522 of the upper pole shoe 52 and the first plate surface is 4.5 mm.

[0074] By setting a preset distance for the pole shoe gap 523, this invention helps to optimize the distribution of the magnetic field inside the pole shoe, avoid excessive concentration or dispersion of the magnetic field, and thus improve the focusing accuracy of the electron beam.

[0075] In one embodiment, such as Figure 2 As shown, the frustum portion 522 includes a cylinder and a frustum. The cylinder is located near the upper pole shoe 52 so that the hollow area formed between the frustum portion 522 and the second sleeve 524 can better place the focusing magnetic lens 53, ensuring the installation reliability of the focusing magnetic lens 53.

[0076] In one embodiment, such as Figure 3 As shown, each of the quadrupole magnetic lenses 6 includes one yoke 63 and four sets of quadrupole magnetic coils 634. The central axis of each yoke 63 coincides with the central axis of the drift channel 54. Each yoke 63 includes four yoke protrusions 631. The four yoke protrusions 631 of each yoke 63 are arranged sequentially around the central axis of the yoke 63 and are oriented towards the central axis. The included angle between two adjacent yoke protrusions 631 of each yoke 63 is 90°. Each yoke protrusion 631 is wound with a set of quadrupole magnetic coils 634, so that the magnetic poles of any two adjacent yoke protrusions 631 are opposite. The second drift tube 65 passes through the central axis of each yoke 63 in sequence, and each yoke 63 is fixed to the outer wall of the second drift tube 65.

[0077] Specifically, such as Figure 3 As shown, the marks I1 and I2 on each quadrupole magnetic coil 634 indicate the direction of the current, corresponding to the magnetic N and S of the magnetic yoke protrusion 631 and the magnetic field lines formed therein. From this, it can be determined that, assuming the direction of the electron beam is outward from the paper, the direction of the converging force of the first quadrupole magnetic lens 61 on the left is the AA' direction in the figure, and the direction of the converging force of the second quadrupole magnetic lens 62 on the right is the BB' direction in the figure. The two converging force directions are orthogonal.

[0078] If the electron beam first passes through the first quadrupole magnetic lens 61 on the left side of the figure, the magnetic field causes the electron beam to be linearly compressed and focused in the AA' direction, while diverging in the BB' direction perpendicular to it; since the double magnetic lens has a flat structure, it can change the electron velocity in a short time, and then the electrons gradually converge (or diverge) during the subsequent drift process; when the electron beam exits from the first quadrupole magnetic lens 61 on the left side and enters the second quadrupole magnetic lens 62, the second quadrupole magnetic lens 62 is rotated by 90° compared to the converging force direction of the first quadrupole magnetic lens 61;

[0079] The electron beam diverging in the first quadrupole lens 61, BB' direction, is focused by the second quadrupole lens 62. The electron trajectory first expands and then converges. Due to the linear increase of the magnetic field in the central region along the radial direction, the electrons diverging in the first quadrupole lens 61 along BB' direction are subject to a large converging effect, thus being strongly compressed. At the same time, the electron beam focusing in the first quadrupole lens 61, AA' direction, diverges in the second quadrupole lens 62. However, since the electrons focused in the first quadrupole lens 61 along AA' direction are close to the central axis, and the magnetic field strength at the central axis linearly decreases to 0, the divergence effect of the electrons converged in the first quadrupole lens 61 along AA' direction in the second quadrupole lens 62 is much lower than the focusing effect of the first quadrupole lens 61. The overall effect is still focused, and the focal size is reduced in both the AA' and BB' directions.

[0080] In one embodiment, such as Figure 3 As shown, the individual yoke protrusions 631 in one of the magnetic yokes 63 are connected by an annular frame 633 with a recessed structure 632.

[0081] The present invention provides a recessed structure 632, which can serve as a positioning mark for the positions of each magnetic yoke protrusion 631, thereby enabling more accurate installation of the magnetic yoke 63 to ensure the focusing direction of the quadrupole magnetic lens 6 on the electron beam; at the same time, the ring structure facilitates installation and fixation, improving ease of use.

[0082] In one embodiment, the quadrupole magnetic coil 634 is made of enameled copper wire.

[0083] The quadrupole magnetic coil 634 and focusing coil 531 of the present invention are made of enameled copper wire with good conductivity and mechanical strength, which can effectively conduct current and generate magnetic field, while ensuring the stability and durability of the coil.

[0084] In one embodiment, the yoke 63 in the quadrupole lens 6 is provided with a coolant fluid channel.

[0085] This invention provides a coolant flow channel within the magnetic yoke 63, which helps dissipate heat, ensures the stability and reliability of the microfocus X-ray tube during high-power operation, and prevents damage to the microfocus X-ray tube due to magnetic field changes caused by overheating, thus making it more suitable for various application scenarios of the microfocus X-ray tube.

[0086] In one embodiment, the yoke 63 is made of soft iron, soft magnetic alloy, or cold-rolled silicon steel sheet.

[0087] This invention, by setting the material of the magnetic yoke 63 to be soft iron, soft magnetic alloy or cold-rolled silicon steel sheet with good magnetic properties, can effectively guide and confine the magnetic field, improve the strength and uniformity of the magnetic field, and thus improve the focusing ability of the electron beam.

[0088] In one embodiment, the exit port of the electron acceleration structure and the inlet port of the first drift tube 41 are connected by a rubber ring seal; the inlet port of the drift channel 54 is connected to the exit port of the first drift tube 41 by a rubber ring seal; the exit port of the drift channel 54 is connected to the inlet port of the second drift tube 65 by a seal; and the exit port of the second drift tube 65 is connected to the transmission target 7 by a rubber ring seal.

[0089] This invention uses rubber rings to seal the connection points through which the electron beam passes, ensuring the airtightness of the electron beam propagation channel environment, preventing external impurities and gases from entering, and guaranteeing the vacuum environment inside the microfocus X-ray tube, thereby improving the stability of the electron beam and the X-ray generation efficiency.

[0090] In summary, the microfocus X-ray tube of the present invention, when used in conjunction with a combination of pole shoe magnetic lenses and quadrupole magnetic lenses, enables two-step focusing of the electron beam. This allows the electron beam to be focused to a very small size, achieving high-resolution imaging and precise electron beam size control, thus meeting the development needs of microfocus X-ray sources for higher spatial resolution. Furthermore, by adjusting the materials of the pole shoes and yoke, the focusing effect on the electron beam can be further improved, further enhancing the spatial resolution of the X-ray source. Additionally, by incorporating multiple levels of quadrupole magnetic lenses and / or multiple sets of monopole magnetic lenses, the focusing accuracy and focusing effect controllability of the electron beam can be further improved. Finally, the coolant flow channel on the yoke allows for enhanced heat dissipation to meet the application requirements of the X-ray tube.

[0091] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0092] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A microfocus X-ray tube, characterized in that, The microfocus X-ray tube includes: a vacuum cavity, an electron acceleration structure, a first drift tube, a collimation structure, a pole piece magnetic lens structure, a quadrupole magnetic lens structure, a second drift tube, and a transmission target; The vacuum chamber is provided with the electron acceleration structure, the outlet of the electron acceleration structure is sealed and connected to the inlet of the first drift tube, and the collimation structure is provided in the first drift tube near the outlet of the electron acceleration structure. The pole shoe magnetic lens structure includes at least one set of single pole shoe magnetic lenses. A drift channel is provided through the pole shoe magnetic lens structure, and the drift channel passes through the central through hole of each single pole shoe magnetic lens. The inlet of the drift channel is sealed and connected to the outlet of the first drift tube, and the outlet of the drift channel is sealed and connected to the inlet of the second drift tube. The quadrupole magnetic lens structure includes at least one quadrupole magnetic lens group, and each quadrupole magnetic lens group includes two quadrupole magnetic lenses with orthogonal focusing directions. The second drift tube passes through the magnetic yoke central axis of each quadrupole magnetic lens in sequence. The outlet of the second drift tube is sealed to the transmission target.

2. The microfocus X-ray tube according to claim 1, characterized in that: The electron acceleration structure includes a high-voltage socket, a cathode, a grid, and an anode. The high-voltage socket is electrically connected to the cathode to provide a negative high voltage, and the anode is grounded. The grid is located between the cathode and the anode, close to the cathode. The anode is at a predetermined distance from the grid and the cathode to form an acceleration region. The exit port of the electron acceleration structure is located on the anode.

3. The microfocus X-ray tube according to claim 1, characterized in that: The collimation structure is a deflection coil, which surrounds the first drift tube near the exit port of the electron acceleration structure.

4. The microfocus X-ray tube according to claim 1, characterized in that: Each set of the single pole shoe magnetic lenses includes a lower pole shoe, an upper pole shoe, and a focusing magnetic lens, wherein the lower pole shoe is located near the first drift tube; The lower pole shoe is a first sleeve including a first top cover and a first opening, and the upper pole shoe is a second sleeve including a second top cover and a second opening, wherein the first opening and the second opening are fitted and fixed together; the first top cover includes a first plate surface, and the first plate surface has an injection hole corresponding to the drift channel. The second top cover includes a second plate and a frustum portion, and the drift channel passes through the center of the second plate and the frustum portion; the first bottom surface of the frustum portion is fixedly connected to the second plate, and there is a predetermined distance between the second bottom surface of the frustum portion and the first plate to form a gap, and the area of ​​the first bottom surface of the frustum portion is larger than the area of ​​the second bottom surface; there are two symmetrical hollow regions between the frustum portion and the second sleeve, and a focusing magnetic lens is provided in each hollow region; the focusing magnetic lens includes a focusing coil and a coil frame, and the focusing coil surrounds the coil frame and is fixedly connected to the upper pole shoe.

5. The microfocus X-ray tube according to claim 4, characterized in that: The upper and lower pole shoes are made of pure iron or electrical pure iron DT4C, the coil frame is made of aluminum alloy, and the focusing coil is made of enameled copper wire.

6. The microfocus X-ray tube according to claim 4, characterized in that: The preset distance between the second bottom surface of the frustum portion of the upper pole shoe and the first plate surface is 3 mm to 6 mm.

7. The microfocus X-ray tube according to claim 1, characterized in that: Each quadrupole magnetic lens includes one yoke and four sets of quadrupole magnetic coils. The central axis of each yoke coincides with the central axis of the drift channel. Each yoke includes four yoke protrusions, which are arranged sequentially around the central axis of the yoke and facing the central axis. The included angle between two adjacent yoke protrusions of each yoke is 90°. Each yoke protrusion is wound with one set of quadrupole magnetic coils, such that the magnetic poles of any two adjacent yoke protrusions are opposite. The second drift tube passes through the central axis of each yoke sequentially, and each yoke is fixed to the outer wall of the second drift tube.

8. The microfocus X-ray tube according to claim 7, characterized in that: The yoke in the quadrupole magnetic lens is provided with a coolant fluid channel.

9. The microfocus X-ray tube according to claim 7, characterized in that: The yoke is made of soft iron, soft magnetic alloy or cold-rolled silicon steel sheet.

10. The microfocus X-ray tube according to any one of claims 1-9, characterized in that: The exit port of the electron acceleration structure and the inlet port of the first drift tube are sealed and connected by a rubber ring; the inlet port of the drift channel and the exit port of the first drift tube are connected by a rubber ring; the exit port of the drift channel and the inlet port of the second drift tube are connected by a sealed fit; the exit port of the second drift tube and the transmission target are sealed and connected by a rubber ring.

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