Neutron source system
By setting up a bunching device in the neutron source system and optimizing the emission port design, the problems of secondary electron suppression and beam divergence were solved, the system stability and focusing effect were improved, and equipment damage and heat load were reduced.
Patent Information
- Application Number
- CN202422128173.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-09-16
- Estimated Expiration
- 2034-08-30
AI Technical Summary
In existing neutron source systems, the secondary electron suppression scheme is ineffective, resulting in a decrease in vacuum and damage to the equipment, while the ion beam divergence is unstable.
A bunching device is set between the ion source and the target assembly to generate a magnetic field to bind secondary electrons and form an electron cloud in a specific area to neutralize the space charge of the ion beam. A uniform magnetic field is formed using devices such as solenoid magnets or annular permanent magnets, and the emission port design is optimized to uniform the ion beam density.
It effectively suppresses secondary electron backflow, reduces vacuum drop and equipment damage, improves the stability of the neutron source system and the focusing effect of the ion beam, reduces space charge effect, and avoids local overheating.
Smart Images
Figure CN223348839U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of neutron generators, and specifically provides a neutron source system. Background Art
[0002] Neutron sources, a crucial platform for nuclear technology applications, emit ion beams from their internal ion sources, bombarding target materials to produce neutrons. However, during this process, the ion beam bombarding the target generates a large number of secondary electrons. Due to the electric field, these secondary electrons are accelerated in reverse and collide with the ion source, or with the inner walls of the vacuum chamber and electrodes, causing damage to the metal surface and desorption of adsorbed gases, leading to a decrease in vacuum and triggering high-voltage discharges. This not only affects the stability of neutron production but can also damage the neutron source equipment.
[0003] In related technologies, common secondary electron suppression methods include electrical suppression and magnetic deflection. Electrical suppression is typically achieved by insulating the target from the suppression electrode and applying a voltage to the target that is positive relative to the suppression electrode potential. This allows the use of bias voltage to suppress secondary electrons. However, electrical suppression requires precise adjustment of the positive bias voltage on the target. If the voltage is too low, secondary electrons may not be effectively suppressed, while if the voltage is too high, it may lead to a loss of acceleration voltage, thereby reducing ion energy.
[0004] Magnetic deflection uses the deflection effect of a magnetic field on charged particles to reduce the back-bombardment of the ion source by secondary electrons. However, in practice, the magnetic field strength may be unevenly distributed, and the magnet arrangement may be inappropriate. This can lead to unstable suppression of secondary electrons by the magnetic field, and the secondary electrons may bombard the deflection magnets and electrodes, causing damage to them.
[0005] In view of this, a new neutron source solution is needed in this field to solve the above problems. Utility Model Content
[0006] The present application aims to solve the above technical problems, namely, to solve the problems of poor effect and beam divergence of existing secondary electron suppression solutions.
[0007] The present application provides a neutron source system, comprising:
[0008] an ion source for generating an ion beam;
[0009] a target assembly, which is arranged opposite to the ion source;
[0010] a first accelerating electrode disposed between the ion source and the target assembly, so that the ion beam bombards the target assembly under the action of the first accelerating electrode, thereby generating neutrons;
[0011] A bunching device is provided between the ion source and the target assembly, and can generate a magnetic field to confine secondary electrons generated when the ion beam bombards the target assembly within the magnetic field.
[0012] Optionally, the bunching device is surrounded by the outside of the first accelerating electrode.
[0013] Optionally, the bunching device is a solenoid magnet.
[0014] Optionally, a plurality of the solenoid magnets are provided, and the plurality of solenoid magnets are spaced apart along the axis direction of the magnetic field.
[0015] Optionally, the bunching device is a ring-shaped permanent magnet.
[0016] Optionally, a plurality of the annular permanent magnets are provided, and the plurality of the annular permanent magnets are spaced apart along the axial direction of the magnetic field.
[0017] Optionally, a plurality of emission ports are provided on the emission surface of the ion source.
[0018] Optionally, the launch port includes:
[0019] a first emission port, which is arranged at the center of the emission surface;
[0020] There are a plurality of second launching ports, and the plurality of second launching ports are spaced apart along the circumference of the first launching port.
[0021] Optionally, the caliber of the second launch port is larger than the caliber of the first launch port.
[0022] Optionally, the neutron source system further includes:
[0023] A second accelerating electrode is disposed between the ion source and the first accelerating electrode.
[0024] When the above technical solution is adopted, the neutron source system provided in the present application is provided with a bunching device between the ion source and the target assembly, and the bunching device is used to generate a magnetic field to confine secondary electrons inside the magnetic field.
[0025] On the one hand, such a structural design can prevent secondary electrons from flowing back to the ion source, or from impacting and sputtering onto the vacuum chamber and the inner wall of the electrode, affecting the performance of the neutron source system.
[0026] On the other hand, secondary electrons, under the influence of a magnetic field, can form an electron cloud in a specific area. When the ion beam emitted from the ion source passes through the electron cloud, the space charge in the ion beam is neutralized by the electrons in the electron cloud. This process can effectively reduce the space charge effect of the ion beam and prevent the ion beam from diverging. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The preferred embodiments of the present application are described below with reference to the accompanying drawings, in which:
[0028] Figure 1 is a schematic structural diagram of a neutron source system according to one embodiment of the present application;
[0029] Figure 2 is a schematic structural diagram of an emitting surface according to an embodiment of the present application;
[0030] Figure 3 It is a structural schematic diagram of a neutron source system according to another embodiment of the present application.
[0031] List of reference numerals:
[0032] 1- ion source, 2- target assembly, 31- first accelerating electrode, 32- second accelerating electrode, 4- solenoid magnet, 5- electron cloud, 61- first emission port, 62- second emission port. DETAILED DESCRIPTION
[0033] The preferred embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely intended to illustrate the technical principles of the present application and are not intended to limit the scope of protection of the present application. Those skilled in the art may adjust these embodiments as needed to suit specific applications.
[0034] It should be noted that, in the description of this application, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the relevant devices or components must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, ordinal numbers such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0035] Furthermore, it should be noted that, in the description of this application, unless otherwise specified or limited, the terms "installed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.
[0036] Neutron sources, as an important platform for nuclear technology applications, generate neutrons by bombarding a target with an ion beam emitted from an internal ion source. However, secondary electrons are also generated during the ion beam bombardment of the target.
[0037] Because there is an electric field between the ion source and the target, these secondary electrons will be accelerated in the reverse direction and collide with the ion source under the action of the electric field, which may cause damage to the neutron source equipment, or sputter onto the inner wall of the vacuum chamber and the electrode, causing damage to the metal surface and desorption of the adsorbed gas, resulting in a decrease in the vacuum degree, and then triggering high-voltage discharge, which will not only affect the stability of neutron production, but may also cause damage to the neutron source equipment.
[0038] Therefore, please refer to Figure 1 , is a neutron source system provided according to one embodiment of the present application. In this embodiment, a suppression magnetic field or a suppression electric field is constructed between the ion source 1 and the target assembly 2 to confine the secondary electrons in a specific area to prevent the backflow of the secondary electrons.
[0039] Specifically, the neutron source system in this embodiment includes an ion source 1 and a target assembly 2 positioned opposite the ion source 1. Both the ion source 1 and the target assembly 2 are located in a vacuum chamber, with a first accelerating electrode 31 positioned between them. The first accelerating electrode 31 is used to generate an accelerating electric field. The ion beam generated by the ion source 1 bombards the target assembly 2 under the influence of this accelerating electric field, thereby generating neutrons. Simultaneously, secondary electrons also escape from the surface of the target assembly 2 during the bombardment process.
[0040] Furthermore, a bunching device is provided between the ion source 1 and the target assembly 2 , and the bunching device is used to generate a magnetic field to confine the secondary electrons inside the magnetic field.
[0041] Specifically, magnetic fields can be generated by electromagnetic coils or magnets. A characteristic of magnetic fields is their axial symmetry. Unlike the magnetic field created by a secondary magnet, which only deflects the direction of secondary electrons, the axial symmetry of the magnetic field causes secondary electrons to move along a spiral trajectory in the magnetic field under the influence of the Lorentz force.
[0042] Such a structural design can, on the one hand, prevent secondary electrons from flowing back to the ion source 1 or from impacting and sputtering onto the inner wall of the vacuum chamber, thereby improving the stability of the neutron source system.
[0043] On the other hand, when the ion beam emitted from the ion source 1 passes through the electron cloud 5, the space charge in the ion beam is neutralized by the electrons in the electron cloud 5. This process can effectively reduce the space charge effect of the ion beam and prevent the ion beam from diverging.
[0044] Specifically, ion beams carry certain charges during transmission. These charges can cause mutual repulsion between beams, forming a space charge effect, which may lead to divergence and instability of the ion beams.
[0045] The formation of electron cloud 5 helps solve this problem. Electron cloud 5 is a stable group of electrons formed under the influence of a magnetic field. As the ion beam passes through electron cloud 5, the electrons in electron cloud 5 interact with the ions in the ion beam, neutralizing the charge in the ion beam. In this way, the electrons in electron cloud 5 absorb or replenish excess charge in the ion beam, reducing the space charge effect in the ion beam. With this reduced space charge effect, the repulsive force of the ion beam is weakened, the beam becomes more stable, and a good focusing effect is maintained.
[0046] From this, it can be seen that the bunching device provided in this embodiment can not only suppress secondary electrons, but also form an electron cloud 5 in a specific area, thereby reducing the space charge effect of the ion beam and improving the focusing effect of the ion beam.
[0047] In one embodiment, the first accelerating electrode 31 is a cylindrical electrode. When a high voltage is applied to the cylindrical electrode, a relatively uniform electric field is formed therein. When the ion beam passes through the electric field, it is affected by the electric field force, thereby accelerating the ion beam along the axis of the cylindrical electrode toward the target assembly 2.
[0048] Furthermore, the focusing device can be an electromagnetic coil or magnet, which is placed around the outside of the cylindrical electrode to help generate a more uniform magnetic field. Due to its symmetry, the magnetic field can provide a symmetrical focusing force in space, helping to confine the trajectory of secondary electrons to a specific area, for example, confining them around the magnetic field.
[0049] Of course, it also helps to reduce the spread of the ion beam, so that the ion beam remains focused.
[0050] In addition, arranging the bunching device outside the cylindrical electrode allows the bunching device to fully utilize the available space, which also helps to simplify the installation process of the equipment.
[0051] In one embodiment, the focusing device utilizes a solenoid magnet 4. A solenoid magnet 4 generates a magnetic field by winding a wire into a spiral coil. When current passes through the solenoid, a uniform, axisymmetric magnetic field is generated within it. As described above, this axisymmetric magnetic field helps confine the trajectory of secondary electrons to a specific region and enhances ion beam focusing.
[0052] In one embodiment, reference Figure 1 As shown, multiple solenoid magnets 4 are provided, and the multiple solenoid magnets 4 are spaced apart along the axis of the magnetic field. This design can reduce the uneven magnetic field distribution at both ends of the solenoid magnets 4 and improve the uniformity of the magnetic field. The axis of the magnetic field can be understood as the axis of the cylindrical electrode.
[0053] Specifically, the magnetic field generated by each solenoid magnet 4 is relatively uniform in its central area, but there will be an "edge effect" at the two ends of the solenoid magnet 4. The "edge effect" can be understood as the phenomenon that the magnetic field of a single solenoid magnet 4 has uneven distribution and bending of magnetic field lines at its two end areas. This phenomenon will cause the magnetic field strength and direction at its two end areas to change.
[0054] In this embodiment, multiple solenoid magnets 4 are spaced apart so that their magnetic fields overlap the edges of adjacent magnets. This allows the magnetic fields of adjacent solenoid magnets 4 to overlap, making the magnetic field strength more uniform and reducing the "edge effect" of each magnet, resulting in a more uniform overall magnetic field distribution.
[0055] This more uniform magnetic field helps control the path and state of secondary electrons, ensuring that they move along the expected trajectory. It also helps provide symmetrical focusing force for the ion beam, improving the focusing effect of the ion beam.
[0056] In a real-time example, Figure 1 As shown, there are preferably three solenoid magnets 4, and the three solenoid magnets 4 are arranged at equal intervals along the axial direction.
[0057] The design of three solenoid magnets 4 spaced apart along the axis effectively improves magnetic field uniformity. This design reduces the edge effects of individual magnets by superimposing and compensating the magnetic fields of multiple magnets, thereby achieving a more uniform magnetic field distribution. This uniform magnetic field helps stabilize secondary electrons, keeping them within the predetermined magnetic field region.
[0058] In one embodiment, the bunching device is a ring-shaped permanent magnet. The ring-shaped permanent magnet can generate a relatively uniform magnetic field region within it. Due to the uniformity of the internal magnetic field, the secondary electrons are subjected to a stable Lorentz force when passing through the ring-shaped permanent magnet, thereby being effectively confined within the predetermined magnetic field region.
[0059] Furthermore, the ring-shaped permanent magnets do not require a continuous current supply, thus reducing energy consumption and maintenance costs.
[0060] In one embodiment, a plurality of annular permanent magnets are provided, and the plurality of annular permanent magnets are spaced apart along the axis of the magnetic field. This design can effectively optimize the magnetic field distribution and improve the uniformity of the magnetic field distribution.
[0061] Specifically, similar to the design of multiple solenoid magnets 4 in the aforementioned embodiment, by arranging multiple annular permanent magnets along the axis, the magnetic field is formed into a more uniform region through the superposition effect of the multiple annular magnets. The magnetic field generated by each annular permanent magnet forms stable magnetic lines of force in the space surrounding it, and the configuration of multiple magnets can reduce fluctuations in local magnetic field strength.
[0062] Furthermore, the uniform magnetic field not only helps stabilize the ion beam, but also helps effectively confine secondary electrons, ensuring that the secondary electrons move within a predetermined area and reducing interference with the ion source 1 .
[0063] Since in a neutron source system, the ion beam current drawn out by the ion source 1 generally exhibits a Gaussian-like distribution, this distribution characteristic has a significant impact on the performance and heat dissipation of the system.
[0064] Specifically, the Gaussian-like distribution refers to the distribution of the ion beam density that is similar to the Gaussian function, that is, the density is highest in the center of the ion beam and gradually decreases in the peripheral area, resulting in uneven energy distribution of the ion beam.
[0065] When the ion beam strikes the target assembly 2 to generate neutrons, a small portion of the ion beam's energy is consumed, but the vast majority of the energy is deposited on the target assembly 2 in the form of heat. This is because the impact of the ion beam causes the atoms or molecules of the target to vibrate and generate heat, thereby converting energy into thermal energy.
[0066] Due to the central concentration of the ion beam, the energy density in the central region is typically higher, resulting in localized overheating of the target assembly 2. Overheating can affect the physical and chemical properties of the target. For example, the target material may experience thermal expansion, material deterioration, or degradation, which can affect the performance and lifespan of the target assembly 2.
[0067] In the prior art, the ion source 1 has a single aperture on its emission surface to guide the ion beam. This single aperture design makes the distribution of the extracted ion beam more similar to that of a Gaussian function. As described above, this structure can easily cause localized overheating of the target, thus affecting its performance.
[0068] Therefore, in one embodiment, the structure of the emission hole is changed to reduce the phenomenon that the ion beam has the highest density in the center and the density is low in the peripheral area, so that the ion beam can impact the target assembly 2 in a more uniform manner.
[0069] Specifically, the ion source 1 is configured with multiple emission apertures on its emission surface, each of which directs a portion of the ion beam, thereby reducing the beam density of a single aperture. This design helps to achieve a more uniform beam density distribution, thereby effectively preventing the generation of localized high temperatures when the ion beam acts on the target assembly 2.
[0070] Furthermore, multiple emission ports are evenly distributed on the emission surface of the ion source 1. After the ion beams are extracted from these emission ports, they overlap in a spatial region near the target assembly 2 under the combined action of the accelerating electric and magnetic fields in the extraction system, where they are simultaneously accelerated and focused. The extraction system comprises a first accelerating electrode 31 and a bunching device.
[0071] Beam overlap can reduce the density concentration of a single beam and increase the overall uniformity of the ion beam.
[0072] In one embodiment, the shape of the emission port is preferably circular, which helps to reduce the problem of beam unevenness caused by irregular edges of the emission port, thereby achieving a more uniform beam distribution and optimizing the focusing effect.
[0073] Furthermore, by changing the aperture of the emission port or optimizing the arrangement of the emission ports, the intensity and distribution of the overall beam can be adjusted.
[0074] In one embodiment, Figure 2 As shown, the launch port includes a first launch port 61 and a second launch port 62 . The first launch port 61 is set at the center of the launch surface, and a plurality of second launch ports 62 are provided. The plurality of second launch ports 62 are evenly spaced around the circumference of the first launch port 61 .
[0075] Such a centrally symmetrical arrangement enables the beams emitted from each emission port to overlap evenly in space when approaching the target assembly 2 .
[0076] In one embodiment, if Figure 2 As shown, the diameter of the second emission port 62 is larger than that of the first emission port 61 . This design helps to reduce the density of the beam in the central area, thereby avoiding local overheating of the target assembly 2 .
[0077] Specifically, by increasing the aperture of the second emission port 62, it is possible to prevent a large amount of beam current from being concentrated in the center, reducing the concentration of the beam current in the central area and thus avoiding the risk of local overheating of the target assembly 2. Furthermore, increasing the aperture of the second emission port 62 also helps disperse the beam current emitted from the second emission port 62 over a larger area, increasing the distribution range of the ion beam current on the target assembly 2. This helps to disperse heat over a larger area, thereby reducing the thermal load on a certain area of the target assembly 2.
[0078] One embodiment, such as Figure 3 As shown, the neutron source system further includes a second accelerating electrode 32, which is disposed between the ion source 1 and the first accelerating electrode 31. This design is mainly applied to large neutron source equipment requiring multi-stage acceleration.
[0079] Specifically, in large-scale neutron source equipment, in order to achieve sufficiently high beam energy and density, a multi-stage acceleration process is usually required. Therefore, multiple accelerating electrodes are required between the ion source 1 and the target assembly 2 to gradually increase the beam energy.
[0080] As part of the multi-stage acceleration system, the second accelerating electrode 32 initially accelerates the ion beam output by the ion source 1. The accelerated ion beam then enters the first accelerating electrode 31 for further acceleration, further increasing the energy of the entire ion beam. This ensures that the ion beam reaches the required high energy level before reaching the target assembly 2.
[0081] At the same time, in the neutron source system provided in this embodiment, the bunching device as described above is provided outside the first accelerating electrode 31, which can effectively control and suppress the movement of secondary electrons and further optimize the focusing effect of the ion beam.
[0082] Thus far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.
Claims
1. A neutron source system, characterized in that: include: an ion source for generating an ion beam; a target assembly, which is arranged opposite to the ion source; a first accelerating electrode disposed between the ion source and the target assembly, so that the ion beam bombards the target assembly under the action of the first accelerating electrode, thereby generating neutrons; A bunching device is provided between the ion source and the target assembly, and can generate a magnetic field to confine secondary electrons generated when the ion beam bombards the target assembly within the magnetic field.
2. The neutron source system according to claim 1, characterized in that The bunching device surrounds the outer side of the first accelerating electrode.
3. The neutron source system according to claim 2, characterized in that The bunching device is a solenoid magnet.
4. The neutron source system according to claim 3, characterized in that A plurality of the solenoid magnets are provided, and the plurality of solenoid magnets are spaced apart along the axis direction of the magnetic field.
5. The neutron source system according to claim 2, characterized in that: The bunching device is an annular permanent magnet.
6. The neutron source system according to claim 5, characterized in that There are multiple annular permanent magnets, and the multiple annular permanent magnets are spaced apart along the axial direction of the magnetic field.
7. The neutron source system according to any one of claims 1 to 6, characterized in that: A plurality of emission ports are provided on the emission surface of the ion source.
8. The neutron source system according to claim 7, characterized in that The launch port includes: a first emission port, which is arranged at the center of the emission surface; There are a plurality of second launching ports, and the plurality of second launching ports are spaced apart along the circumference of the first launching port.
9. The neutron source system according to claim 8, characterized in that The diameter of the second launch port is larger than that of the first launch port.
10. The neutron source system according to claim 1, wherein: The neutron source system further includes: A second accelerating electrode is disposed between the ion source and the first accelerating electrode.