Adjustable cold cathode X-ray tube

Abstract

The present invention discloses an adjustable cold cathode X-ray tube, comprising an upper porcelain tube and a lower porcelain tube, an anode component is provided at the lower end of the lower porcelain tube, a grid is provided between the upper porcelain tube and the lower porcelain tube, a cold cathode and a focusing electrode are provided in the upper porcelain tube, and the distances between the cold cathode and the focusing electrode relative to the grid can be adjusted separately. The present invention can realize operation under various voltage conditions by adjusting the axial positions of the focusing electrode and the cathode, thereby obtaining X-rays with different short-wave limits; similarly, by adjusting the axial positions of the focusing electrode and the cathode, anode currents of different sizes can be obtained under the same or different operating voltages, thereby obtaining X-rays with different short-wave limits and different intensities. It is not only simple to operate, but also has the function of more conveniently adjusting the electron beam convergence effect, and has a larger adjustment range, which is conducive to forming a smaller focus. At the same time, the structure of the cold cathode X-ray tube can optimize the aging process and improve the yield of the product.

Description

Technical Field

[0001] The invention relates to the field of field emission technology and electric vacuum device, and in particular to an adjustable cold cathode X-ray tube. Background Art

[0002] Field emission technology: When a certain electric field is applied to the cathode substrate coating layer of field emission, due to the tunneling effect, a portion of high-energy electrons near the Fermi level will pass through the cathode surface barrier, overflow the surface and fly to the anode to form a current. This process does not require additional energy to excite electrons, and has the characteristics of fast response, low energy loss, and high emission efficiency. In addition, because nanomaterials are used as electron sources, the volume is small, and the X-ray tube structure is compact, which reduces the size of the X-ray tube focus, so that it can meet many current market requirements for X-ray tubes.

[0003] Although field emission cathodes have shown excellent performance and great development potential as electron sources for X-ray tubes, there are also many problems that need to be solved. For example: ① Whether the cathode surface coating material is graphene or carbon nanotubes, it is easily affected by external factors during the growth process, and the growth uniformity is difficult to ensure, resulting in inconsistent current emission density of each cold cathode; ② The long-term working stability of cold cathode ray tubes needs to be improved. On the one hand, due to the small diameter of the cold cathode itself and the small contact area between the coating and the substrate, the connection is poor, which increases the resistance of the connection. The heat generated during continuous operation may cause damage to part of the coating. On the other hand, secondary electron bombardment may be generated during long-term operation, which will also cause continuous accumulation of heat and eventually burn the surface coating, resulting in a decrease in the emission current density, a decrease in the number of electrons generated by the electron beam hitting the target, and a decrease in output power. These situations require means such as adjusting the focal spot size to focus more electron beams on the target to ensure the stability of the output power.

[0004] Generally, an X-ray tube only works within a very narrow operating voltage range, that is, the adjustable range of the operating voltage is too small, and the short-wave limit of the generated X-rays is basically fixed, which limits the working efficiency of the whole machine and makes it difficult to achieve multiple uses of one X-ray tube. Summary of the invention

[0005] In order to make up for the shortcomings of the prior art, the present invention provides an adjustable cold cathode X-ray tube, which is not only simple to operate and has a more convenient function of adjusting the electron beam convergence, but also has a larger adjustment range. On the one hand, it is conducive to forming a smaller focus, and on the other hand, it can also realize the change of the operating voltage within a larger range or the change of different currents under the same voltage. At the same time, the structure of the cold cathode X-ray tube can optimize the aging process and improve the reliability of the product.

[0006] The technical solution adopted by the present invention to solve its technical problems is: an adjustable cold cathode X-ray tube, comprising an upper porcelain tube and a lower porcelain tube, an anode component is provided at the lower end of the lower porcelain tube, a grid is provided between the upper porcelain tube and the lower porcelain tube, a cold cathode and a focusing electrode are provided in the upper porcelain tube, and the distances between the cold cathode and the focusing electrode relative to the grid can be adjusted separately.

[0007] As a further improvement of the present invention, the top opening of the upper porcelain tube is provided with a cathode flange and a focusing electrode bottom plate. The focusing electrode is cylindrical and placed in the upper porcelain tube. The top of the focusing electrode movably passes through the cathode flange and is fixedly connected to the focusing electrode bottom plate. The focusing electrode bottom plate is provided with a plurality of adjustment lugs extending outward, each of which is provided with a first through hole and a focusing electrode adjustment screw is provided in the first through hole. A first adjustment threaded hole is correspondingly provided on the cathode flange, and a locking nut is sleeved on the threaded end of the focusing electrode adjustment screw and then screwed into the first adjustment threaded hole. An outer bellows and an inner bellows are respectively provided on the outside of the focusing electrode portion located between the cathode flange and the focusing electrode bottom plate, and the upper and lower ends of the outer bellows and the inner bellows are respectively fixed to the cathode flange and the focusing electrode bottom plate.

[0008] As a further improvement of the present invention, an adjustment hole is provided at the center of the focusing pole bottom plate.

[0009] As a further improvement of the present invention, the cold cathode is arranged on a cathode seat, and the cathode seat can be slid up and down and placed in the bottom of the focusing electrode, and the upper end of the cathode seat is fixedly connected to the cathode flange through a central bellows; a second threaded through hole is provided at the center of the cathode flange, and a limiting groove is provided at the center of the upper side surface of the cathode seat, and a cathode adjusting screw is also provided to pass through the second threaded through hole on the cathode flange to the limiting groove on the cathode seat through threaded engagement, and the cathode adjusting screw can rotate radially and stop axially relative to the limiting groove.

[0010] As a further improvement of the present invention, the cold cathode includes a substrate and a coating layer coated on the substrate, the base material of the substrate is a metal or alloy containing iron or nickel, and the coating layer is carbon nanotubes or graphene.

[0011] As a further improvement of the present invention, a limiting boss is provided at the end of the cathode adjusting screw, and a limiting groove is correspondingly provided in the limiting slot, and the limiting boss is clamped in the limiting groove.

[0012] As a further improvement of the present invention, there are at least two adjusting lugs, which are evenly arranged on the periphery of the focusing pole bottom plate.

[0013] As a further improvement of the present invention, a positioning groove is provided on the bottom plate of the focusing electrode, and the top of the focusing electrode is inserted into the positioning groove.

[0014] As a further improvement of the present invention, the anode component includes an anode and a target material disposed on the anode.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention can achieve different operating voltages of the X-ray tube by adjusting the axial positions of the focusing electrode and the cathode, and correspondingly obtain X-rays with different short-wave limits, which is suitable for different application occasions;

[0017] 2. The present invention can achieve different electric field strengths on the cathode surface of the X-ray tube by adjusting the axial positions of the focusing electrode and the cathode, and correspondingly obtain cathode currents of different sizes, thereby affecting the intensity of the X-rays, and can be selected according to different application scenarios;

[0018] 3. Due to various factors, there are serious inconsistencies in the emission characteristics of cold cathodes. By adjusting the axial position of the focusing electrode and the cathode, the emission current and the quality of X-rays can meet the use requirements within the working voltage range, which can largely make up for the poor consistency of cathode emission performance and make cold cathode ray tubes more suitable for batch production management;

[0019] 4. Keep the cathode position unchanged, use the axial telescopic structure to push the focusing electrode toward the grid. When the position is appropriate, add a high voltage between the focusing electrode and the grid for purification, which can improve the working reliability of the X-ray tube. At the same time, due to the shielding effect of the focusing electrode, the high voltage cannot pull out the cathode current, and naturally no X-rays will be generated. Therefore, no protective measures are required for the entire purification process of the focusing electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the cross-sectional structure of this utility model;

[0022] Figure 3 for Figure 1 A top view of

[0023] Figure 4 It is a schematic diagram of the exploded structure of the focusing electrode assembly of the present invention;

[0024] Figure 5 It is a schematic diagram of the assembly state of the focusing electrode assembly of the present invention;

[0025] Figure 6 It is a schematic structural diagram of the cold cathode assembly of the present invention.

[0026] Combined with the attached drawings, the following description is given:

[0027] 1a——upper porcelain tube; 1b——lower porcelain tube;

[0028] 2——anode component; 3——grid;

[0029] 21——anode; 22——target;

[0030] 4——cold cathode; 5——focusing electrode;

[0031] 6——cathode flange; 61——first adjustment threaded hole;

[0032] 62——second threaded through hole; 7——locking nut;

[0033] 8——focusing pole bottom plate; 81——adjustment hole;

[0034] 82——Location slot; 9——Adjustment lug;

[0035] 91——first through hole; 10——focusing pole adjustment screw;

[0036] 11——outer bellows; 12——inner bellows;

[0037] 13——cathode seat; 14——center bellows;

[0038] 15——Cathode adjusting screw; 16——Limiting slot. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0040] See also Figure 1-6 , is an adjustable cold cathode X-ray tube described in the present invention, comprising an upper porcelain tube 1a and a lower porcelain tube 1b, an anode component 2 is provided at the lower end of the lower porcelain tube 1b, a grid 3 is provided between the upper porcelain tube 1a and the lower porcelain tube 1b, a cold cathode 4 and a focusing electrode 5 are provided in the upper porcelain tube 1a, and the distances between the cold cathode 4 and the focusing electrode 5 relative to the grid 3 can be adjusted separately, as described in detail below.

[0041] The top opening of the upper porcelain tube 1a is provided with a cathode flange 6, and a focusing electrode bottom plate 8 is also provided. The focusing electrode 5 is cylindrical and placed in the upper porcelain tube 1a. The top of the focusing electrode 5 movably passes through the cathode flange 6 and is fixedly connected to the focusing electrode bottom plate 8. The focusing electrode bottom plate 8 is provided with a plurality of outwardly extending adjustment lugs 9, each of which is provided with a first through hole 91 and a focusing electrode adjustment screw 10 is provided in the first through hole 91. The cathode flange 6 is correspondingly provided with a first adjustment threaded hole 61, and the threaded end of the focusing electrode adjustment screw 10 passes through the adjustment lug. 9 is connected to the first through hole 91 of the focusing electrode 5 and then to the first adjusting threaded hole 61. At the same time, a locking nut 7 is arranged on the outer surface of the threaded end of the focusing electrode adjusting screw 10 and located between the adjusting lug 9 and the cathode flange 6. The locking nut 7 and the focusing electrode adjusting screw 10 are connected by threaded engagement. The outer portion of the focusing electrode 5 located between the cathode flange 6 and the focusing electrode bottom plate 8 is respectively provided with an outer bellows 11 and an inner bellows 12. The upper and lower ends of the outer bellows 11 and the inner bellows 12 are respectively fixed on the cathode flange 6 and the focusing electrode bottom plate 8. When it is necessary to adjust the focusing electrode 5, first loosen the locking nut 7 and rotate the focusing electrode adjusting screw 10. When the focusing electrode adjusting screw 10 rotates, the lower end of the focusing electrode adjusting screw 10 is screwed into or out of the first adjusting threaded hole 61 correspondingly provided on the cathode flange 6, and at the same time, the outer bellows 11 and the inner bellows 12 located between the cathode flange 6 and the focusing electrode bottom plate 8 are squeezed or stretched, so that the focusing electrode 5 is raised and lowered relative to the cathode flange 6 as the focusing electrode adjusting screw 10 rotates. After adjusting the focusing electrode 5 to the required position, loosen the focusing electrode adjusting screw 10, rotate the locking nut 7 until it is tightly attached to the focusing electrode bottom plate 8, lock the focusing electrode adjusting screw 10, and complete the adjustment of the axial position of the focusing electrode 5.

[0042] The center of the focusing electrode bottom plate 8 is provided with an adjustment hole 81, which is convenient for adjusting the cold cathode. The cold cathode 4 is arranged on the cathode seat 13, and the cathode seat 13 can be slid up and down and placed in the bottom of the focusing electrode 5. The upper end of the cathode seat 13 is fixedly connected to the cathode flange 6 through the central bellows 14; the center of the cathode flange is provided with a second threaded through hole 62, and the center of the upper side surface of the cathode seat 13 is provided with a limiting groove 16. A cathode adjustment screw 15 is also provided, which passes through the second threaded through hole 62 on the cathode flange 6 to the limiting groove 16 on the cathode seat 13 through threaded engagement. The cathode adjustment screw 15 can rotate radially and stop axially relative to the limiting groove 16. The specific structure can be: a limiting boss is provided at the end of the cathode adjustment screw 15, and a limiting groove is correspondingly provided in the limiting groove 16, and the limiting boss is clamped in the limiting groove. When the cold cathode 4 needs to be adjusted, the focusing electrode base plate 8 is entered through the adjustment hole 81 provided in the center of the focusing electrode base plate 8, and the cathode adjustment screw 15 can be rotated manually or with the help of a tool. When the cathode adjustment screw 15 is rotated, its bottom is connected by a limiting boss and a limiting groove 16, that is, the cathode adjustment screw 15 can be radially rotated and axially stopped relative to the limiting groove 16. At the same time, since the upper end of the cathode adjustment screw 15 and the second threaded through hole 62 on the cathode flange 6 are threadedly engaged, when the cathode adjustment screw 15 is rotated, the cathode adjustment screw 15 will drive the cathode seat 13 and the cold cathode 4 to rise and fall relative to the cathode flange 6, and squeeze or stretch the central bellows, thereby realizing the adjustment of the axial position of the cold cathode 4.

[0043] Among them, the cold cathode 4 includes a substrate and a coating layer coated on the substrate, the base material of the substrate is a metal or alloy containing iron and nickel, and the coating layer is carbon nanotubes or graphene; the number of the adjusting lugs 9 is at least two, which are evenly arranged on the periphery of the focusing electrode bottom plate 8. In this embodiment, three are taken as an example, and the specific number is not limited; a positioning groove 82 is provided on the focusing electrode bottom plate 8, and the top of the focusing electrode 5 is inserted into the positioning groove; the anode component 2 includes an anode 21 and a target material 22 provided on the anode, and the target material 22 can be selected from a tungsten target, a molybdenum target, etc., and the present invention does not make specific limitations.

[0044] In the adjustable cold cathode X-ray tube, the focusing pole is cylindrical, and its barrel passes through the cathode flange, so that the inner bellows surrounds the inner side of the barrel of the focusing pole, and the outer bellows surrounds the outer side of the barrel of the focusing pole. One end of the two bellows is connected to the bottom plate of the focusing pole, and the other end is connected to the bottom plate of the cathode flange. The two bellows are concentric with the barrel of the focusing pole to form a focusing pole adjustment structure. When the focusing pole needs to be adjusted, the focusing pole adjustment screw is rotated to drive the bottom plate of the focusing pole and the barrel of the focusing pole to move axially relative to the cathode flange, so that the inner and outer bellows between the bottom plate of the focusing pole and the cathode flange have a stroke, thereby changing the distance between the focusing pole and the cold cathode (or grid). After the position adjustment of the focusing pole is completed, tighten the locking nut 7 to fix the barrel position of the focusing pole, and the adjustment of the focusing pole is completed.

[0045] The cold cathode is placed on the cathode seat, and the two ends of the central bellows are respectively connected to the bottom of the cathode seat and the top of the cathode flange to form a cathode adjustment structure. When the position of the cold cathode needs to be adjusted, the length of the central bellows can be changed by adjusting the cathode adjustment screw through the adjustment hole 81, so that the cathode seat moves on the inner wall of the barrel of the focusing electrode, and the cold cathode is moved closer to or away from the grid, so as to change the distance between the position of the cold cathode and the grid or the anode.

[0046] When the adjustable cold cathode X-ray tube is in use, negative and positive high voltages are applied to the cathode and anode ends, and the grid is grounded. Under different power-on conditions, by changing the positions of the cold cathode and the focusing electrode in the adjustable component, different emission currents or different light spots can be obtained, thereby obtaining an ideal radiation dose, which is beneficial to improving the emission consistency of the electron source, and improving the working stability and yield of the product, so that the product can meet the application under various conditions. The following examples are given.

[0047] We know that the continuous X-ray spectrum has a wavelength limit in the short-wave direction, called the short-wave limit λ0, which is the X-ray produced by the exhaustion of energy by a single collision of photons. It is only related to the tube voltage V and is not affected by other factors. That is, each tube voltage V corresponds to a certain short-wave limit λ 0。

[0048] The shorter the X-ray wavelength, the less the substance absorbs it and the greater its penetrating power. People often use different penetrating powers and the different degrees of absorption by different substances to perform X-ray fluoroscopy, photography and protection.

[0049] The present invention can realize working under various voltage conditions by adjusting the axial positions of the focusing electrode and the cathode, thereby obtaining X-rays with different short-wave limits; similarly, by adjusting the axial positions of the focusing electrode and the cathode, different anode currents can be obtained under the same working voltage, thereby obtaining X-rays with different intensities. The following only takes three working modes of a certain adjustable X-ray tube as an example for explanation.

[0050] In the first working mode:

[0051] Cathode voltage Vc = -35KV, anode voltage Va = 80KV, current Ia = 9.5mA, λ0 = 0.0108nm, focal (focal spot) < 1mm × 1mm;

[0052] In the second working mode,

[0053] Cathode voltage Vc = -51KV, anode voltage Va = 80KV, current Ia = 5.2mA, λ0 = 0.0095nm, focal (focal spot) < 1mm × 1mm;

[0054] In the third working mode,

[0055] Cathode voltage Vc=-80KV, anode voltage Va=80KV, current Ia=23mA, λ0=0.0078nm, focal (focal spot)<1mm×1mm.

[0056] The above three modes achieve the span of the X-ray tube operating voltage from 115kV to 160kV, and the corresponding short-wave limit is shortened from 0.0108nm to 0.0078nm, and the current also changes from 5mA to 23mA, while ensuring the acquisition of a suitable focal spot size (less than 1mm×1mm). All of this is achieved by adjusting the axial position of the focusing electrode and the cathode. The adjustment range of the focusing electrode and the cathode in this case is not less than 6 mm, which is within the adjustable range of the present invention.

[0057] It can be seen that the adjustable cold cathode X-ray tube, in which the cathode and the focusing electrode can be adjusted separately, can be widely used in industrial X-ray imaging equipment such as medical treatment, security inspection, and industry. It has many advantages such as high voltage, low power consumption, fast response, small size, high resolution, long working life, and low radiation dose.

[0058] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An adjustable cold cathode X-ray tube, comprising an upper porcelain tube (1a) and a lower porcelain tube (1b), wherein an anode component (2) is provided at the lower end of the lower porcelain tube (1b), a grid (3) is provided between the upper porcelain tube (1a) and the lower porcelain tube (1b), and a cold cathode (4) and a focusing electrode (5) are provided in the upper porcelain tube (1a), characterized in that: The distances between the cold cathode (4) and the focusing electrode (5) relative to the grid (3) can be adjusted individually; The top opening of the upper porcelain tube (1a) is provided with a cathode flange (6) and a focusing electrode bottom plate (8). The focusing electrode (5) is cylindrical and is placed in the upper porcelain tube (1a). The top of the focusing electrode (5) movably passes through the cathode flange (6) and is fixedly connected to the focusing electrode bottom plate (8). The focusing electrode bottom plate (8) is provided with a plurality of outwardly extending adjustment lugs (9). Each adjustment lug (9) is provided with a first through hole (91) and a focusing electrode adjustment screw (10) is provided in the first through hole (91). A first adjusting threaded hole (61) is correspondingly provided on the cathode flange (6), and a locking nut (7) is sleeved on the threaded end of the focusing electrode adjusting screw (10) and then screwed into the first adjusting threaded hole (61); an outer bellows (11) and an inner bellows (12) are respectively provided on the outside of the focusing electrode (5) located between the cathode flange (6) and the focusing electrode bottom plate (8), and the upper and lower ends of the outer bellows (11) and the inner bellows (12) are respectively fixed on the cathode flange (6) and the focusing electrode bottom plate (8); An adjustment hole (81) is provided at the center of the focusing electrode bottom plate (8); the cold cathode (4) is provided on a cathode seat (13), and the cathode seat (13) can be slid up and down and placed in the bottom of the focusing electrode (5); the upper end of the cathode seat (13) is fixedly connected to the cathode flange (6) through a central bellows (14); a second threaded through hole (62) is provided at the center of the cathode flange, and a limiting groove (16) is provided at the center of the upper side surface of the cathode seat (13); a cathode adjustment screw (15) is also provided, which passes through the second threaded through hole (62) on the cathode flange (6) to the limiting groove (16) on the cathode seat (13) through threaded engagement, and the cathode adjustment screw (15) can rotate radially and stop axially relative to the limiting groove (16).

2. The adjustable cold cathode X-ray tube according to claim 1, characterized in that: The cold cathode (4) comprises a substrate and a coating layer coated on the substrate, the base material of the substrate is a metal or alloy containing iron or nickel, and the coating layer is carbon nanotubes or graphene.

3. The adjustable cold cathode X-ray tube according to claim 1, characterized in that: A limiting boss is provided at the end of the cathode adjusting screw (15), and a limiting groove is correspondingly provided in the limiting groove (16), and the limiting boss is clamped in the limiting groove.

4. The adjustable cold cathode X-ray tube according to claim 1, characterized in that: There are at least two adjusting lugs (9) which are evenly arranged on the periphery of the focusing pole bottom plate (8).

5. The adjustable cold cathode X-ray tube according to claim 1, characterized in that: The focusing electrode bottom plate (8) is provided with a positioning groove (82), and the top of the focusing electrode (5) is inserted into the positioning groove.

6. The adjustable cold cathode X-ray tube according to claim 1, characterized in that: The anode component (2) comprises an anode (21) and a target material (22) disposed on the anode.

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