CN117612912A - Double focusing cold cathode electron gun for micro focus X ray tube - Google Patents
Double focusing cold cathode electron gun for micro focus X ray tube Download PDFInfo
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- CN117612912A CN117612912A CN202410088702.3A CN202410088702A CN117612912A CN 117612912 A CN117612912 A CN 117612912A CN 202410088702 A CN202410088702 A CN 202410088702A CN 117612912 A CN117612912 A CN 117612912A
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- ray tube
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- 238000010894 electron beam technology Methods 0.000 claims abstract description 29
- 230000005540 biological transmission Effects 0.000 claims abstract description 13
- 238000010586 diagram Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/58—Arrangements for focusing or reflecting ray or beam
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/485—Construction of the gun or of parts thereof
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- X-Ray Techniques (AREA)
Abstract
The invention relates to an electron gun, in particular to a twice focusing cold cathode electron gun for a micro-focus X-ray tube, which comprises a cathode, a grid, a first focusing electrode, a second focusing electrode and an anode which are coaxially and sequentially arranged, wherein an electron emission area is arranged on the cathode, a concave structure with a concave surface facing the grid is arranged on the end face of one end of the cathode, which is close to the grid, and the electron emission area is positioned in the concave structure; the electron beam transmission channel in the second focusing electrode is of a non-central symmetrical structure. Through the concave structure arranged on the cathode, and the electron emission area is placed in the concave structure, the two focusing electrodes which are matched and introduced and the non-central symmetrical structure adopted by the second focusing electrode electron beam transmission through hole reduce the grid interception current and focus the electron beam twice, so that the focus with adjustable size in two mutually orthogonal directions is obtained, and the minimum size of the focus can reach 2 mu m.
Description
Technical Field
The invention relates to an electron gun, in particular to a double-focusing cold cathode electron gun for a micro-focus X-ray tube.
Background
The X-ray tube is used as an important ray source and is widely applied to the fields of medicine, industry, scientific research and the like. With the continuous progress of technology, the requirements of people on the resolution, penetration imaging capability and detection result precision of the X-ray tube are continuously improved, and a micro-focus X-ray tube is generated. While a key component of a microfocus X-ray tube is an electron gun, which is capable of achieving microfocus electron beam spots. At present, electron guns which can be used in micro-focus X-ray tubes have the problems of large focus size, low electron beam energy and the like.
A multi-stage focusing cathode electron gun for a very micro focus X-ray tube as disclosed in chinese patent publication No. CN206363980U, the electron gun comprising a cathode, a grid, a compensation electrode and a focusing electrode, wherein the compensation electrode is added between the grid and the focusing electrode to ensure that electrons have a minimum emittance increase after passing through the grid, so that focusing of the electron beam is easier, the compensation electrode does not focus the electron beam, and thus the obtained focal size is larger.
Another example is an electron gun disclosed in chinese patent publication No. CN204885080U, which mainly includes a stem, a heat support, a first stage grid, a second stage grid and a third stage grid, the first stage grid converging electrons emitted by the heat, the second stage grid being for accelerating the electrons and controlling the tube flow, the third stage grid converging the electron beam and finally focusing it to form a focal point with a size as low as 5 μm, the electrons being focused only once in the whole process.
As disclosed in chinese patent publication No. CN1744265a, electrons of the electron gun are pre-focused after being emitted from the cathode and passing through the control electrode, and then secondarily focused and accelerated through two focusing lenses consisting of the first anode, the focusing electrode and the second anode, so that the energy of the electron beam is low and the electron gun is suitable for cathode ray tubes.
Disclosure of Invention
In view of this, the present invention provides a double focusing cold cathode electron gun for a micro focus X-ray tube to solve the problems that the existing electron gun is difficult to obtain a smaller size focus and has poor versatility.
In order to solve the problems, the invention adopts the following technical scheme:
a twice focusing cold cathode electron gun for micro focus X ray tube includes cathode, grid, first focusing electrode, second focusing electrode and anode set coaxially;
an electron emission region is arranged on the cathode, a concave structure with a concave surface facing the grid is arranged on the end face of one end of the cathode, which is close to the grid, and the electron emission region is positioned in the concave structure;
the electron beam transmission channel in the second focusing electrode is of a non-central symmetrical structure.
Further, the non-centrosymmetric structure is rectangular.
Further, the concave structure is a curved structure or a cylindrical structure with a concave surface facing the grid electrode.
Further, when the concave structure is a curved structure with a concave surface facing the grid, the curvature radius of the curved surface is 0.4-mm-0.6 mm.
Further, when the concave structure is a cylindrical structure with a concave surface facing the grid electrode, the diameter of the cylindrical structure is 0.8-1.2 mm.
Further, the diameter of the electron beam transmission channel in the first focusing electrode is slightly larger than the diameter of the concave structure or the chord of the curved surface structure.
The invention provides a double focusing cold cathode electron gun for a micro focus X ray tube, wherein an electron emission area of the electron gun is positioned in a cathode concave structure, and a grid electrode is used for providing electric field intensity required by field emission cathode emission electrons. When the electron emission region emits electron beams, the concave structure can primarily converge the emitted electron beams, at this time, the cathode, the grid electrode and the first focusing electrode form a first focusing lens, the first focusing electrode, the second focusing electrode and the anode target form a second focusing lens, the electron beam track forms a first focus at the grid electrode under the action of the first focusing lens, and forms a second focus output with smaller size at the target surface of the anode under the action of the second focusing lens.
Compared with the prior art, the invention has the advantages that through the concave structure arranged on the cathode, the electron emission area is placed in the concave structure, the two focusing electrodes are matched and the second focusing electrode electron beam transmission through hole adopts the non-central symmetry structure, the grid intercepting current is reduced, the electron beam is focused twice, the focus with adjustable size in two mutually orthogonal directions is obtained, and the minimum size of the focus can reach 2 mu m.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a double-focusing cold cathode electron gun according to an embodiment;
FIG. 2 is a schematic cross-sectional view of a second focus of a double-focus cold cathode electron gun according to an embodiment;
FIG. 3 is a schematic diagram of the shapes of the focal point and the effective focal point obtained by the twice-focusing cold cathode electron gun according to the embodiment;
FIG. 4 is a schematic diagram of the shape of the focal point and the effective focal point obtained after focusing the second focusing electrode in the double focusing cold cathode electron gun according to the embodiment;
FIG. 5 is a schematic view of a concave structure with a curved surface in an embodiment;
FIG. 6 is a schematic view of a concave structure in a cylindrical shape in an embodiment;
reference numerals:
1. cathode, 2 grid, 3, first focusing electrode, 4, second focusing electrode, 5, concave structure, 6, first focus, 7, second focus, 8, anode, 9, target angle.
Description of the embodiments
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
As shown in fig. 1 to 6, a double focusing cold cathode electron gun for a micro focus X-ray tube of the present embodiment includes a cathode 1, a grid 2, a first focusing electrode 3, a second focusing electrode 4, and an anode 8 coaxially disposed in this order. An electron emission region is arranged on the cathode 1, and a concave structure 5 with a concave surface facing the grid electrode is arranged on the end face of one end of the cathode 1, which is close to the grid electrode 2. The electron emission regions are located within the recess structures 5. The cross section of the electron beam transmission channel in the second focusing electrode 4 is of a non-central symmetrical structure, so that the electron beam transmission channel at the second focusing electrode 4 is unequal in size in the horizontal direction and the vertical direction, and the cross section is preferably rectangular.
In this embodiment, the concave structure 5 on the cathode may be a curved structure with a concave surface facing the gate, or may be a cylindrical structure with a concave surface facing the gate, and when the concave structure 5 is a curved structure, the radius of curvature is 0.5 mm; when the concave structure 5 is a cylindrical structure, the diameter is 1.0. 1.0 mm. The diameter of the electron emission surface is 300-400 mu m, the diameter of the electron beam transmission channel of the first focusing electrode 3 is 1-2 mm, and the section of the electron beam transmission channel of the second focusing electrode 4 is rectangular. The diameter of the electron beam transmission channel in the first focusing electrode 3 is slightly larger than the diameter of the cylindrical structure or the chord of the curved surface structure.
In implementation, the cathode 1 is grounded, the voltage of the grid electrode 2 is set to be 1500-2500 and V positive voltage, the first focusing electrode 3 is set to be 500-1000V positive voltage, the voltage of the second focusing electrode 4 is adjustable to be 2000-3000V, and 130-KV-180 KV high voltage is applied to the anode 8. After the electron beam is emitted from the electron emission region, the concave structure 5 can primarily converge the emitted electron beam, the cathode 1, the grid electrode 2 and the first focusing electrode 3 form a first focusing lens, the first focusing electrode 3, the second focusing electrode 4 and the anode 8 form a second focusing lens, the electron beam track forms a first focus 6 at the grid electrode 2 under the action of the first focusing lens, and a second focus 7 as low as 2 mu m is formed at the target surface of the anode 8 under the action of the second focusing lens for output.
In this embodiment, since the cross section of the electron beam transmission channel in the second focusing electrode 4 is rectangular, the horizontal width is different from the vertical width, when the horizontal width is smaller than the vertical width, the dimension of the electron beam in the horizontal direction is compressed, the dimension of the focal point in the horizontal direction is also compressed, and the ratio of the horizontal dimension X to the vertical dimension Y of the electron beam focal point is different under different voltages of the second focusing electrode 4, so as to compensate the influence of the target angle 9 of the anode 8 on the effective focal point dimension. Fig. 3 shows a focal shape and an effective focal shape obtained by focusing using a centrosymmetric structure, and fig. 4 shows a focal shape and an effective focal shape obtained by focusing using a second focusing electrode 4 having a non-centrosymmetric structure. Comparing fig. 3 and 4, it can be seen that the use of the second focusing electrode 4 having a non-centrosymmetric structure can obtain an effective focal spot having a more uniform shape.
The above embodiments are only for illustrating the technical solution of the present invention, and should not be construed as limiting the scope of the present invention, and any insubstantial changes and substitutions made by those skilled in the art on the basis of the present invention are intended to fall within the scope of the present invention as claimed.
Claims (6)
1. A cold cathode electron gun for micro focus X-ray tube with twice focusing, comprising a cathode, a grid, a first focusing electrode, a second focusing electrode and an anode which are coaxially arranged in sequence, characterized in that:
an electron emission region is arranged on the cathode, a concave structure with a concave surface facing the grid is arranged on the end face of one end of the cathode, which is close to the grid, and the electron emission region is positioned in the concave structure;
the electron beam transmission channel in the second focusing electrode is of a non-central symmetrical structure.
2. A bifocal cold cathode electron gun for a microfocus X-ray tube according to claim 1, wherein: the non-central symmetrical structure is rectangular.
3. A bifocal cold cathode electron gun for a microfocus X-ray tube according to claim 1, wherein: the concave structure is a curved surface structure or a cylindrical structure with a concave surface facing the grid electrode.
4. A bifocal cold cathode electron gun for a microfocus X-ray tube according to claim 3, wherein: when the concave structure is a curved surface structure with a concave surface facing the grid electrode, the curvature radius of the curved surface is 0.4-mm-0.6 mm.
5. A bifocal cold cathode electron gun for a microfocus X-ray tube according to claim 3, wherein: when the concave structure is a cylindrical structure with a concave surface facing the grid electrode, the diameter of the cylindrical structure is 0.8-1.2 mm.
6. A bifocal cold cathode electron gun for a microfocus X-ray tube according to claim 1, wherein: the diameter of the electron beam transmission channel in the first focusing electrode is slightly larger than the diameter of the concave structure or the chord of the curved surface structure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410088702.3A CN117612912A (en) | 2024-01-22 | 2024-01-22 | Double focusing cold cathode electron gun for micro focus X ray tube |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410088702.3A CN117612912A (en) | 2024-01-22 | 2024-01-22 | Double focusing cold cathode electron gun for micro focus X ray tube |
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| Publication Number | Publication Date |
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| CN117612912A true CN117612912A (en) | 2024-02-27 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202410088702.3A Pending CN117612912A (en) | 2024-01-22 | 2024-01-22 | Double focusing cold cathode electron gun for micro focus X ray tube |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117637417A (en) * | 2024-01-24 | 2024-03-01 | 电子科技大学 | Micro-focus electron gun using aperture structure for auxiliary focusing |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030198318A1 (en) * | 2002-04-17 | 2003-10-23 | Ge Medical Systems Global Technology Company, Llc | X-ray source and method having cathode with curved emission surface |
| CN104362062A (en) * | 2014-10-30 | 2015-02-18 | 中国科学院深圳先进技术研究院 | Cold cathode focused X-ray tube |
| KR20180097430A (en) * | 2017-02-23 | 2018-08-31 | 박흥균 | Line Type Focused Electron Beam Emission Device |
| CN117174552A (en) * | 2023-08-01 | 2023-12-05 | 中山大学 | Cold cathode electron gun with electron beam shape adjustable coplanar quadrupole focusing structure |
| CN117174557A (en) * | 2023-11-03 | 2023-12-05 | 上海超群检测科技股份有限公司 | High-energy micro-focus X-ray tube |
-
2024
- 2024-01-22 CN CN202410088702.3A patent/CN117612912A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030198318A1 (en) * | 2002-04-17 | 2003-10-23 | Ge Medical Systems Global Technology Company, Llc | X-ray source and method having cathode with curved emission surface |
| CN104362062A (en) * | 2014-10-30 | 2015-02-18 | 中国科学院深圳先进技术研究院 | Cold cathode focused X-ray tube |
| KR20180097430A (en) * | 2017-02-23 | 2018-08-31 | 박흥균 | Line Type Focused Electron Beam Emission Device |
| CN117174552A (en) * | 2023-08-01 | 2023-12-05 | 中山大学 | Cold cathode electron gun with electron beam shape adjustable coplanar quadrupole focusing structure |
| CN117174557A (en) * | 2023-11-03 | 2023-12-05 | 上海超群检测科技股份有限公司 | High-energy micro-focus X-ray tube |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117637417A (en) * | 2024-01-24 | 2024-03-01 | 电子科技大学 | Micro-focus electron gun using aperture structure for auxiliary focusing |
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Inventor after: Wang Yan Inventor after: Yu Siming Inventor before: Wang Yan Inventor before: Zhang Pengcheng Inventor before: Yu Siming |
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