Electron extraction device and electron accelerator

Abstract

The utility model discloses an electronic extraction device and electron accelerator, and electron accelerator includes negative high -voltage end and accelerating tube, and electronic extraction device includes high -voltage cathode and high -voltage anode, and high -voltage cathode is connected with negative high -voltage end, and high -voltage cathode includes first cylinder and hot cathode, and hot cathode is located on high -voltage cathode axis, and first cylinder is located below hot cathode, and high -voltage anode includes integrally formed second cylinder and anode cylinder body, and second cylinder is located in first cylinder, and the top aperture of anode cylinder body is same with second cylinder, and the bottom aperture of anode cylinder body is same with the beam current hole aperture of first electrode piece, and the top aperture of anode cylinder body is less than the bottom aperture. The utility model can increase the contact surface between electric field line and anode cylinder, thereby weakening the lateral focusing force of electric field, reducing the electron beam scattering angle at the beam waist point of electron beam group, and increasing the distance between the beam waist point and the surface of hot cathode, so that the transmission trajectory of electron beam in acceleration is more gathered.

Description

Technical Field

[0001] This utility model relates to an electron extraction device and an electron accelerator. Background Technology

[0002] High-voltage electron accelerators are designed to accelerate electrons. They inject electrons emitted from an electron gun into an accelerating tube. Under the acceleration of the high-intensity electric field formed by the electrodes of the accelerating tube, the electrons quickly approach the speed of light, and their energy quickly reaches hundreds of kilovolts, megavolts, or even tens or hundreds of megaelectron volts. This forms a high-energy electron beam to irradiate and process objects; or it can rotate a target to generate X-rays to irradiate and process large objects or high-density products.

[0003] To ensure that all electron beams reach the accelerator beam outlet safely and stably, existing electron accelerators require a very high voltage difference between the cathode and anode, which greatly increases the difficulty of accelerator fabrication and manufacturing costs. Utility Model Content

[0004] The technical problem to be solved by this invention is to greatly reduce the voltage difference between the anode and cathode while achieving safe and stable output of the electron beam. This invention provides an electron extraction device and electron accelerator that can weaken the lateral focusing force of the electric field by increasing the contact surface between the electric field lines and the anode cylinder, thereby reducing the electron beam scattering angle at the waist of the electron beam and increasing the distance between the waist and the hot cathode surface, thus making the electron beam more focused.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

[0006] An electron extraction device is provided for an electron accelerator, the electron accelerator including a negative high-voltage end and an accelerating tube. The device includes a high-voltage cathode and a high-voltage anode, the high-voltage cathode being connected to the negative high-voltage end. The high-voltage cathode includes a first cylindrical tube and a hot cathode, the hot cathode being disposed on the axis of the high-voltage cathode, and the first cylindrical tube being disposed below the hot cathode. The high-voltage anode includes an integrally formed second cylindrical tube and an anode body. The high-voltage anode is coaxially connected to a first electrode plate of the accelerating tube. The first cylindrical tube and the second cylindrical tube are coaxially arranged, the second cylindrical tube being disposed inside the first cylindrical tube. The top aperture of the anode body is the same as that of the second cylindrical tube, and the bottom aperture of the anode body is the same as that of the beam aperture of the first electrode plate. The top aperture of the anode body is smaller than the bottom aperture.

[0007] Preferably, the high-voltage cathode further includes a third cylindrical tube and a mounting platform. The first cylindrical tube, the mounting platform, and the third cylindrical tube are integrally formed. The mounting platform is disposed between the first cylindrical tube and the third cylindrical tube. The hot cathode is disposed in the mounting platform. The bottom surface of the mounting platform is coplanar with the electron emission surface of the hot cathode.

[0008] Preferably, the intersection of the bottom surface of the mounting platform and the longitudinal section is arc-shaped.

[0009] Preferably, the outer surface of the third cylindrical tube is provided with a first fixing ring, and the first fixing ring is installed on the bottom surface of the negative high-voltage end.

[0010] Preferably, the bottom end of the anode cylinder is provided with a second fixing ring, which is mounted on the upper surface of the first electrode plate.

[0011] Preferably, the lower edge cross-section of the first cylindrical tube is semi-circular, and the upper edge cross-section of the first cylindrical tube is semi-circular.

[0012] Preferably, the top end of the third cylindrical tube is embedded in the mounting groove at the bottom of the negative high-voltage end.

[0013] Preferably, the radius of the electron emitting surface of the hot cathode is smaller than the inner diameter of the second cylindrical tube.

[0014] Preferably, the radius of the electron emitting surface of the hot cathode is greater than 3 mm and less than 5 mm, the inner diameter of the first cylindrical tube is greater than 52 mm and less than 56 mm, the inner diameter of the second cylindrical tube is greater than 23 mm and less than 27 mm, the maximum inner diameter of the anode tube is greater than 33 mm and less than 37 mm, the distance from the electron emitting surface to the top of the second cylindrical tube is greater than 13 mm and less than 14 mm, and the height of the high-voltage anode is greater than 25 mm and less than 27 mm.

[0015] This invention also provides an electron accelerator, characterized in that the electron accelerator includes the electron extraction device described above.

[0016] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this utility model.

[0017] The positive and progressive effects of this utility model are as follows:

[0018] This invention can increase the contact area between the electric field lines and the anode cylinder, thereby weakening the lateral focusing force of the electric field, reducing the electron beam scattering angle at the waist point of the electron beam cluster, and increasing the distance between the waist point and the hot cathode surface, making the electron beam's transmission trajectory more focused during acceleration. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the electronic lead-out device according to Embodiment 1 of the utility model.

[0020] Figure 2 This is another structural schematic diagram of the electronic lead-out device according to Embodiment 1 of the utility model.

[0021] Figure 3This is a schematic diagram of the electron accelerator according to Embodiment 1 of the utility model.

[0022] Figure 4 This is another structural schematic diagram of the electron accelerator of Embodiment 1 of the utility model.

[0023] Figure 5 This is a schematic diagram illustrating the effect of the electronic lead-out device according to Embodiment 1 of the utility model.

[0024] Figure 6 This is a schematic diagram illustrating the effect of the electronic lead-out device according to Embodiment 1 of the utility model. Detailed Implementation

[0025] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0026] Example 1

[0027] In this embodiment, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] See Figures 1 to 4 This embodiment provides an electron accelerator.

[0029] The electron accelerator includes an electron extraction device 10, and the hot cathode of the electron accelerator is disposed on the electron extraction device.

[0030] The electron accelerator also includes a negative high-voltage terminal 11 and an accelerating tube, the accelerating tube including a first electrode plate 12. The first electrode plate is the first electrode plate in the accelerating tube.

[0031] The electron extraction device includes a high-voltage cathode 13 and a high-voltage anode 14, with the high-voltage cathode 13 connected to the negative high-voltage terminal 11.

[0032] The high-voltage cathode 13 includes a first cylindrical tube 131 and a hot cathode 132, with the hot cathode disposed on the axis of the high-voltage cathode.

[0033] The first cylindrical tube is located below the hot cathode, and the high-pressure anode 14 includes an integrally formed second cylindrical tube 141 and an anode tube 142.

[0034] The high-voltage anode is coaxially connected to the first electrode plate, and the first cylindrical tube and the second cylindrical tube are coaxially arranged, with the second cylindrical tube located inside the first cylindrical tube.

[0035] The top aperture of the anode cylinder 142 is the same as that of the second cylindrical cylinder 141, the bottom aperture of the anode cylinder is the same as that of the beam aperture of the first electrode plate, and the top aperture of the anode cylinder is smaller than that of the bottom aperture.

[0036] The high-voltage cathode 13 also includes a third cylindrical tube 133 and a mounting platform 134, wherein the first cylindrical tube, the mounting platform and the third cylindrical tube are integrally formed.

[0037] The mounting platform is located between the first cylindrical tube 131 and the third cylindrical tube 133, and the hot cathode 132 is located in the mounting platform. The bottom surface 1341 of the mounting platform is coplanar with the electron emission surface of the hot cathode.

[0038] To ensure that the electron beam is drawn out uniformly from the lower surface of the hot cathode, and to avoid the hot cathode affecting the overall field distribution, the electron emission surface of the hot cathode is coplanar with the inner top surface of the high-voltage cathode.

[0039] The intersection of the bottom surface of the mounting platform and the longitudinal section is arc-shaped.

[0040] The high-voltage cathode is designed with a "bowl-shaped" concave surface along the lower edge of the cathode structure, and the upper surface of the anode cylinder is placed inside the "bowl-shaped" structure. The purpose is to converge the electric field between the anode and cathode, thereby enhancing the gradient of the electron beam acceleration electric field, improving the acceleration efficiency of the electron beam, and effectively suppressing the negative impact of the space charge effect on the beam quality.

[0041] Because of the voltage difference between the high-voltage cathode and the anode, the electric field lines emanating from the outside of the anode cylinder point towards the high-voltage cathode. This electric field has almost no effect on the beam. However, the electric field lines emanating from the inner surface and top surface of the upper half of the high-voltage anode point towards the inner top surface of the high-voltage cathode, generating a longitudinal electric field that accelerates electrons and a lateral defocusing field that causes electrons to laterally defocus. The electric field lines emanating from the bottom of the anode cylinder point towards the inner surface of the lower half of the high-voltage anode, generating a longitudinal electric field that accelerates electrons and a lateral focusing field that causes electrons to laterally focus. From below the second electrode to the accelerator outlet, because all the electrode plates are designed with equal spacing and gradient, the lateral electric field component within the beam channel is essentially zero.

[0042] Structural dimensional requirements:

[0043] Since the electrons from the hot cathode are drawn into the upper part of the anode cylinder by a defocusing field, the radius of the electron emission surface must be smaller than the inner diameter of the anode cylinder.

[0044] Under the same anode-cathode pressure difference, the closer the distance between the anode and cathode, the better it is to suppress the space charge effect and improve the beam quality. However, at the same time, it faces the risk of breakdown by high voltage electric field. Therefore, the top of the anode tube is inserted into the center of the cathode tube.

[0045] After numerous experiments, the transition from a "trumpet mouth" shape in the middle of the high-pressure anode cylinder effectively suppressed the size of the beam spot.

[0046] Dimensions: The radius of the electron emitting surface of the hot cathode is 4mm; the radius of the inner wall of the high-voltage cathode is 27mm; the inner radius of the upper end of the anode cylinder is 12.5mm, and the inner radius of the lower end is 17.5mm (consistent with the aperture of the electrode plates). The distance between the hot cathode surface and the anode surface is 13.4mm. The height of the anode cylinder is 26mm.

[0047] See Figure 4 The electron beam undergoes an acceleration process under the influence of the extraction structure and is specifically affected by its design. The beam initially encounters a lateral defocusing force, causing the beam spot to gradually expand. Subsequently, the electron beam is subjected to a lateral focusing force, gradually reducing its lateral velocity to zero, and finally accelerating and focusing along the central axis. After passing through the extraction structure, the electron beam passes through a series of electrode plates, including the second and third, before finally reaching the extraction point. During this process, the beam spot reaches its minimum value at a specific location inside the accelerator, defined as the "beam waist." Due to the equidistant and gradient design of the accelerator electrode plates, the lateral electric field force experienced by the electron beam after the "beam waist" is almost zero. Therefore, the main factors determining the size of the beam envelope at the extraction point are the "beam waist" position and the scattering angle of the electron beam at the "beam waist." When the "beam waist" position is far from the hot cathode surface and the scattering angle of the electron beam at that position is small, the beam spot size at the extraction point will be small; conversely, the beam spot size will increase.

[0048] See Figure 5 and Figure 6The lower end of the anode cylinder has a flared structure, with the inner diameter of the flared opening matching the aperture of the electrode plate. The anode cylinder and electrode plate are placed concentrically on the electrode plate. By appropriately setting the size of the flared opening, the contact area between the electric field lines and the anode cylinder can be increased, thereby weakening the lateral focusing force of the electric field. Keeping other hardware unchanged, the electric field distribution experienced by the electron beam in the defocusing region remains essentially constant after designing the "flared" structure. In the focusing region, the longitudinal field component experienced by the electron beam remains essentially constant, while the lateral focusing field becomes weaker, causing electrons to take a longer time to return to the axial direction. Simultaneously, due to the weaker lateral focusing field, the lateral velocity of the electrons first decreases to zero and then accelerates radially. When the electrons leave the focusing electric field region, their lateral focusing velocity decreases. Therefore, the flared structure can simultaneously increase the distance between the "waist" point and the hot cathode surface and reduce the electron beam scattering angle at the "waist" point, thus achieving the goal of controlling the beam envelope.

[0049] The outer surface of the third cylindrical tube is provided with a first fixing ring, which is installed on the bottom surface of the negative high-voltage end.

[0050] The bottom end of the anode cylinder is provided with a second fixing ring, which is installed on the upper surface of the first electrode plate.

[0051] The lower edge of the first cylindrical tube has a semi-circular cross-section, and the upper edge of the first cylindrical tube has a semi-circular cross-section.

[0052] The top of the third cylindrical tube is embedded in the mounting groove at the bottom of the negative high-voltage end.

[0053] The radius of the electron emitting surface of the hot cathode is smaller than the inner diameter of the second cylindrical tube.

[0054] The radius of the electron emitting surface of the hot cathode is greater than 3 mm and less than 5 mm, with a preferred size of 4 mm.

[0055] The inner diameter of the first cylindrical tube is greater than 52 mm and less than 56 mm, with a preferred size of 54 mm.

[0056] The inner diameter of the second cylindrical tube is greater than 23 mm and less than 27 mm, with a preferred size of 25 mm.

[0057] The maximum inner diameter of the anode cylinder is greater than 33 mm and less than 37 mm, with a preferred size of 35 mm.

[0058] The distance from the electron emitting surface to the top of the second cylindrical tube is greater than 13 mm and less than 14 mm, with a preferred dimension of 13.4 mm.

[0059] The height of the high-pressure anode is greater than 25mm and less than 27mm, with 26mm being the preferred size.

[0060] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. An electron extraction device for an electron accelerator, the electron accelerator comprising a negative high-voltage terminal and an accelerating tube, characterized in that, The electron extraction device includes a high-voltage cathode and a high-voltage anode. The high-voltage cathode is connected to the negative high-voltage end. The high-voltage cathode includes a first cylindrical tube and a hot cathode. The hot cathode is disposed on the axis of the high-voltage cathode, and the first cylindrical tube is disposed below the hot cathode. The high-voltage anode includes an integrally formed second cylindrical tube and an anode body. The high-voltage anode is coaxially connected to the first electrode plate of the accelerating tube. The first cylindrical tube and the second cylindrical tube are coaxially arranged. The second cylindrical tube is disposed inside the first cylindrical tube. The top aperture of the anode body is the same as that of the second cylindrical tube, and the bottom aperture of the anode body is the same as that of the beam aperture of the first electrode plate. The top aperture of the anode body is smaller than the bottom aperture.

2. The electronic extraction device as described in claim 1, characterized in that, The high-voltage cathode also includes a third cylindrical tube and a mounting platform. The first cylindrical tube, the mounting platform, and the third cylindrical tube are integrally formed. The mounting platform is located between the first cylindrical tube and the third cylindrical tube. The hot cathode is located in the mounting platform. The bottom surface of the mounting platform is coplanar with the electron emission surface of the hot cathode.

3. The electronic extraction device as described in claim 2, characterized in that, The intersection of the bottom surface of the mounting platform and the longitudinal section is arc-shaped.

4. The electronic extraction device as described in claim 2, characterized in that, The outer surface of the third cylindrical tube is provided with a first fixing ring, which is installed on the bottom surface of the negative high-voltage end.

5. The electronic extraction device as described in claim 4, characterized in that, The bottom end of the anode cylinder is provided with a second fixing ring, which is installed on the upper surface of the first electrode plate.

6. The electronic extraction device as described in claim 4, characterized in that, The lower edge of the first cylindrical tube has a semi-circular cross-section, and the upper edge of the first cylindrical tube has a semi-circular cross-section.

7. The electronic extraction device as described in claim 2, characterized in that, The top of the third cylindrical tube is embedded in the mounting groove at the bottom of the negative high-voltage end.

8. The electronic extraction device as described in claim 2, characterized in that, The radius of the electron emitting surface of the hot cathode is smaller than the inner diameter of the second cylindrical tube.

9. The electronic extraction device as claimed in claim 2, characterized in that, The radius of the electron emitting surface of the hot cathode is greater than 3 mm and less than 5 mm, the inner diameter of the first cylindrical tube is greater than 52 m and less than 56 mm, the inner diameter of the second cylindrical tube is greater than 23 m and less than 27 mm, the maximum inner diameter of the anode tube is greater than 33 m and less than 37 mm, the distance from the electron emitting surface to the top of the second cylindrical tube is greater than 13 mm and less than 14 mm, and the height of the high-voltage anode is greater than 25 mm and less than 27 mm.

10. An electron accelerator, characterized in that, The electron accelerator includes an electron extraction device as described in any one of claims 1 to 9.

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