Soft x-ray tube structure for electrostatic elimination and method for verifying same

Abstract

A soft X-ray tube structure for electrostatic elimination and its verification method are disclosed, belonging to the field of X-ray tubes. A spherical spiral tungsten filament emitting cathode is disposed within the vacuum tube; a spherical cap-shaped beryllium anode target electrode is disposed in front of the spherical spiral tungsten filament emitting cathode, with a tungsten coating deposited on its inner surface; a spherical cap-shaped confinement electrode is disposed behind the spherical spiral tungsten filament emitting cathode; the center points of the spherical cap-shaped beryllium anode target electrode, the spherical cap-shaped confinement electrode, and the spherical spiral tungsten filament emitting cathode are spatially aligned. This design enables uniform, wide solid angle radiation of soft X-rays, thereby significantly improving the electrostatic elimination range; it effectively avoids the thermionic leakage caused by the circular tubular focusing electrode in existing technologies, thus improving the soft X-ray emission efficiency / effectiveness, and consequently improving the electrostatic elimination efficiency / effectiveness; simultaneously, it effectively avoids the reduction in the insulation performance of the vacuum tube bottom surface caused by the sputtering of thermionic electrons themselves.

Description

Technical Field

[0001] This invention belongs to the field of X-ray tubes, and particularly relates to a soft X-ray tube structure for static electricity elimination and its verification method. Background Technology

[0002] With the rapid development of the semiconductor, integrated circuit and optoelectronic industries, the requirements for electrostatic safety and micro-contamination control are gradually increasing.

[0003] Traditional high-voltage corona discharge static eliminators inevitably experience fluctuations in ion balance voltage due to their working principle / method, which can easily exceed the electrostatic safety threshold and cause electrostatic damage to the protected products. Furthermore, as the electrode needles are continuously corroded, they gradually release contaminating particles, making it increasingly difficult for them to meet the requirements of low electrostatic safety thresholds and strict particulate contamination control.

[0004] Traditional high-voltage corona discharge static eliminators apply high voltage to electrode needles to generate corona discharge, which ionizes air molecules and produces positive and negative ions. These positive and negative ions are then transported to the surface of charged objects to eliminate static electricity (also known as static neutralization).

[0005] To completely solve the problems caused by the working principle / method of the aforementioned high-voltage corona discharge electrostatic eliminator, the soft X-ray electrostatic eliminator was developed. It rapidly ionizes air molecules near the surface of a charged object (belonging to radiation ionization) by outputting high-energy rays, generating positive and negative ions to eliminate static charge on the object's surface. It does not produce particulate pollution during the electrostatic elimination process, and the ion balance voltage fluctuation is extremely low (an inherent property of radiation ionization).

[0006] The soft X-ray electrostatic eliminator consists of three main components: a high-voltage generating unit, a filament heating unit, and a soft X-ray tube. It emits soft X-rays (typically in the wavelength range of...). With an energy range of 0.124keV to 12.4keV, it combines a certain degree of ionization and penetration, and is therefore used in the field of static electricity elimination.

[0007] A flexible X-ray tube is a key device for generating flexible X-rays. Its basic structure includes an emitting cathode, an anode target, a focusing electrode, a vacuum tube for sealing (usually a ceramic or glass tube), and a getter. For details on its structure, please refer to the relevant description in the Korean Patent "Protective Device for Shielding X-rays Emitted from an X-ray Tube" with publication number KR101687363B1, publication date 2016.12.16 (application number KR1020150118784A, application date 2015.08.24).

[0008] Soft X-ray tubes are used for static elimination / neutralization, unlike rigid X-ray tubes used in industrial flaw detection / inspection and medical testing industries (typically with a wavelength range of...). Even shorter; energy range of 12.4keV to 124keV, or even higher); soft X-rays produced by soft X-ray tubes must have a certain ionization ability to generate a sufficient number of positive and negative ions; while hard X-rays produced by hard X-ray tubes have strong penetrating power, but weak ionization ability, and thus weak electrostatic elimination ability; and hard X-ray tubes used for detection / inspection require high image resolution, so their structural design must meet the requirement of a small focal spot (this is the main function / role of the focusing electrode), so the X-ray coverage area they emit is small, and the positive and negative ions generated by ionization are limited to a narrow space, which cannot meet the needs of large-scale electrostatic elimination.

[0009] Therefore, in the prior art, such as the Korean patent "Soft X-ray Generator with Improved Antistatic Range and Heat Dissipation" with publication number KR101586342B1, publication date 2016.01.20 (application number KR1020140096000A, application date 2014.07.28), and the Korean patent "X-ray Tube with Extended Radiation Angle" with publication number KR20210021671A, publication date 2021.03.02 (application number KR1020190100846A, application date 2019.08.19), the target electrode (transmission window) structure has been optimized.

[0010] While the aforementioned optimizations have improved the trajectory of thermionic electrons within the X-ray tube to some extent and further expanded the collision area of ​​thermionic electrons on the target electrode, thus increasing the stereo radiation angle of transmitted X-rays, the structure of the target electrode (transmission window) does not completely determine the size of the stereo radiation angle of transmitted X-rays. The size of the stereo radiation angle of transmitted X-rays essentially depends directly on the trajectory of thermionic electrons, that is, on the force (electric field force) characteristics of thermionic electrons. The force characteristics of thermionic electrons are directly determined by the structure and relative positions of the emitting cathode, focusing electrode / binding electrode, and target electrode. However, the existing technology has not performed corresponding matching optimizations for the emitting cathode and focusing electrode / binding electrode used in conjunction with the target electrode. Therefore, the increase in the stereo radiation angle of transmitted X-rays is limited and cannot meet the requirements for electrostatic elimination operations over a wider range.

[0011] In the Japanese patent application "Transmission-type X-ray Generator" with publication number JP2019192450A, publication date 2019.10.31 (application number JP2018082854A, application date 2018.04.24), although the emitting cathode and target electrode are optimized to match each other in order to achieve the invention objective of "expanding the irradiation range while maintaining the intensity and uniformity of X-ray radiation surface", the X-rays transmitted by the emitter adopt a "linear / rod-shaped" design structure, which causes the X-rays to diffuse in an elliptical shape, resulting in uneven radiation power / intensity across the entire radiation receiving surface. Furthermore, the cold cathode design results in a relatively small number of emitted electrons, leading to relatively weak radiation power / intensity of the transmitted X-rays and thus weaker electrostatic discharge capability.

[0012] In summary, the existing technical solutions have the following technical defects:

[0013] 1) The asymmetry and mismatch between the structure of the emitting cathode and the target electrode lead to uneven spatial distribution of the transmitted X-rays, which in turn results in uneven spatial distribution of the ionized positive and negative ions, causing inconsistency in the power dissipation capacity in different directions at the same radial distance.

[0014] 2) Existing target electrode structures are mostly planar or contain planar structures, and the emitting cathodes (mostly cylindrical helical structures, see...) Figure 3-1 The asymmetry between the target electrode and the target electrode (as shown in the diagram) causes a significant portion of the hot electrons' trajectories to be not perpendicular to the target surface, but rather at a certain angle (see...). Figure 1-1 As shown); thus, the generated X-rays will have different transmission absorption distances, which will result in different radiation absorption losses, making the intensity of transmitted X-ray radiation uneven (i.e., different radiation intensities at different stereo angles). Consequently, the number of positive and negative ions ionized at different stereo angles will be different, which will lead to different de-energizing capabilities of charged objects at different angles (because for the same radial distance, the de-energizing capability is strongest at the part directly facing the plane target window, while the de-energizing capability weakens when it is at an inclined angle to the plane target window).

[0015] 3) Due to unreasonable structural design of the focusing electrode and / or thermionic cathode, thermionic electrons only collide with a small part of the anode target surface, the transmitted X-ray stereo radiation angle is small, the coverage area of ​​the ionized positive and negative ions is small, and thus the power elimination range is small; in addition, thermionic electrons also move in directions outside the target electrode, causing corrosion of the vacuum tube wall material, reducing the surface insulation performance of the vacuum tube, and easily causing electrical breakdown of the inner surface of the tube.

[0016] 4) High-speed thermionic electrons collide with the target electrode, inevitably causing sputtering of metal from the target electrode surface. This results in metal particles adhering to the inner surface of the vacuum tube, reducing the surface insulation performance of the vacuum tube and making it prone to electrical breakdown of the inner surface of the tube.

[0017] 5) Compared to hot cathode tubes, cold cathode tubes emit relatively fewer electrons and are more expensive to manufacture. Furthermore, due to the inherent structural characteristics of the cold cathode surface, it is prone to adsorbing gases or other impurities, leading to a decrease in electron emission efficiency.

[0018] How to eliminate the inconsistency in the static elimination capacity of soft X-ray tubes used for static elimination / neutralization in different directions at the same radial distance, and the different radiation intensities at different solid angles, avoid the reduction of the insulation performance of the vacuum tube surface and the problem of metal particles adhering to the inner surface of the vacuum tube, improve the electron emission efficiency, and form a larger soft X-ray solid radiation angle (i.e., achieve uniform and wide solid angle radiation of soft X-rays) is an important technical problem that urgently needs to be solved in actual research and development. Summary of the Invention

[0019] The technical problem to be solved by this invention is to provide a soft X-ray tube structure for electrostatic elimination and its verification method. It adopts a structure of a spherical spiral emitting cathode, a spherical cap-shaped anode target electrode, and a spherical cap-shaped confinement electrode. The center points of the spherical spiral emitting cathode, the spherical cap-shaped anode target electrode, and the spherical cap-shaped confinement electrode are set at the same concentric spherical structure to achieve uniform, wide solid angle radiation of soft X-rays. A radial spatial electric field is formed between the emitting cathode and the anode target electrode, which can generate a larger three-dimensional radiation angle of soft X-rays, thereby significantly improving the electrostatic elimination range. Furthermore, the use of the spherical cap-shaped anode target structure and the spherical cap-shaped confinement electrode allows thermionic electrons to move in a controlled manner towards the spherical cap-shaped anode target, effectively avoiding the thermionic electron spillover caused by the circular tubular focusing electrode in the prior art. This improves the thermionic electron emission utilization efficiency, thereby improving the soft X-ray emission efficiency (or effectiveness), and thus improving the electrostatic elimination efficiency (effectiveness). At the same time, it also effectively avoids the reduction in the insulation performance of the vacuum tube bottom surface caused by the sputtering of thermionic electrons themselves.

[0020] The technical solution of the present invention is: to provide a soft X-ray tube structure for electrostatic elimination, comprising a vacuum tube body, characterized in that:

[0021] A spherical spiral tungsten filament emission cathode is installed inside the vacuum tube;

[0022] The spherical spiral tungsten filament emission cathode is a spherical spiral emission cathode formed by a tungsten filament spirally coiled around a sphere with a radius of R1.

[0023] The spherical spiral tungsten filament emitting cathode is used to emit thermionic electrons;

[0024] In front of the spherical spiral tungsten filament emitting cathode, a spherical cap-shaped anode beryllium target electrode with an opening facing the spherical spiral tungsten filament emitting cathode is set, and a tungsten coating is uniformly deposited on the inner surface of the spherical cap-shaped anode beryllium target electrode.

[0025] The aforementioned spherical cap-shaped anode beryllium target electrode has a spherical cap-shaped curved surface with a radius of R2;

[0026] The aforementioned spherical cap-shaped anode beryllium target electrode is used to receive high-speed thermionic electron impacts emitted by a spherical spiral tungsten filament emitting cathode, and to generate soft X-rays using a tungsten coating, which are then transmitted through a beryllium window to form external radiation.

[0027] A spherical cap-shaped confinement electrode is placed behind the spherical spiral tungsten filament emitting cathode;

[0028] The aforementioned spherical cap-shaped binding electrode has a spherical cap-shaped curved surface with a radius of R3;

[0029] The aforementioned spherical cap-shaped binding electrode is used to constrain the thermionic electrons to move backward, so that the thermionic electrons move in a controlled manner toward the spherical cap-shaped anode target, thereby improving the thermionic electron emission utilization efficiency, improving the soft X-ray emission efficiency, and thus improving the electrostatic elimination efficiency; at the same time, it prevents thermionic electrons from sputtering to the bottom region of the ceramic vacuum tube, avoiding the reduction of the insulation performance of the bottom surface of the vacuum tube caused by the sputtering of the thermionic electrons themselves, so as to maintain the insulation performance of the vacuum tube surface.

[0030] The spatial positions of the center point of the spherical cap-shaped anode beryllium target electrode, the center point of the spherical cap-shaped binding electrode, and the center point of the spherical spiral tungsten wire emitting cathode coincide;

[0031] The spherical spiral tungsten filament emitting cathode, the spherical cap-shaped anode beryllium target electrode, and the spherical cap-shaped confinement electrode together constitute a direction-controlled radial thermionic emission electrode structure.

[0032] Specifically, the spherical radius R1 of the spherical spiral tungsten filament emitting cathode is smaller than the spherical radius R3 of the spherical cap-shaped confinement electrode; the spherical radius R3 of the spherical surface of the spherical confinement electrode is smaller than the spherical radius R2 of the spherical anode beryllium target electrode.

[0033] Specifically, the spherical spiral tungsten filament emitting cathode, the spherical cap-shaped anode beryllium target electrode, and the spherical cap-shaped binding electrode constitute a multi-concentric spherical structure with a common spherical center.

[0034] Furthermore, the spherical cap-shaped confinement electrode is disposed inside the vacuum tube, located behind the spherical spiral tungsten filament emitting cathode; the inner surface of the spherical cap-shaped anode beryllium target electrode is a concave surface of a spherical cap-shaped curved surface, and a tungsten coating is uniformly deposited on the concave surface of the spherical cap-shaped curved surface; the spherical cap-shaped anode beryllium target electrode is disposed at the front end of the vacuum tube, forming a spherical cap-shaped curved protruding beryllium window of the flexible X-ray tube.

[0035] Specifically, a vacuum tube bottom cover is provided at the rear end of the vacuum tube body; several metal leads are provided through the vacuum tube bottom cover; the several metal leads include at least two metal leads constituting a first pair of metal leads and two metal leads constituting a second pair of metal leads; wherein, the front ends of the first pair of metal leads are electrically connected to the two ends of the spherical spiral tungsten filament emitting cathode respectively; the front ends of the second pair of metal leads are electrically connected to the spherical cap-shaped confinement electrode; the spherical spiral tungsten filament emitting cathode and the spherical cap-shaped confinement electrode are electrically insulated from each other.

[0036] Furthermore, a pair of through holes are provided on the spherical surface of the cap-shaped binding electrode to allow the two metal leads constituting the first pair of metal leads to pass through the spherical surface of the cap-shaped binding electrode in an electrically insulating manner.

[0037] Furthermore, the two metal leads constituting the first pair of metal leads and the two metal leads constituting the second pair of metal leads are structurally isolated and electrically insulated from each other; on the bottom cover plate of the vacuum tube, the two pairs of metal leads are arranged orthogonally.

[0038] The technical solution of the present invention also provides a method for verifying the above-mentioned soft X-ray tube structure for electrostatic elimination, characterized in that the verification method includes:

[0039] 1) Construct models of the existing soft X-ray tube electrode structure and the soft X-ray tube electrode structure of this technical solution in finite element software or simulation software respectively;

[0040] 2) For soft X-ray tubes, apply electromagnetic-Joule heat transfer and surface-to-surface radiation mathematical models;

[0041] 3) Mesh the entire flexible X-ray tube, perform simulation calculations, and obtain the thermal field distribution of the flexible X-ray tube;

[0042] 4) Applying an electrostatic field mathematical model to flexible X-ray tubes;

[0043] 5) For the vacuum space inside the soft X-ray tube, apply a mathematical model of charged particle motion in an electric field, where the temperature field distribution of the thermionic emission boundary condition must be obtained from thermal field simulation data.

[0044] 6) Mesh the soft X-ray tube, perform simulation calculations, and obtain simulation results of the hot electron motion characteristics;

[0045] 7) Analyze and compare the characteristics of thermionic displacement, energy, and transport current exhibited by different flexible X-ray tube structures;

[0046] 8) By analyzing the thermionic electron transport probability, average electron kinetic energy, and the magnitude and density distribution of the transport current to the target electrode, a soft X-ray tube electrode system structure that is more suitable for large stereo radiation angles and uniform radiation intensity can be determined.

[0047] Specifically, the electromagnetic-Joule heat transfer mathematical model is as follows:

[0048]

[0049] J = σE

[0050]

[0051] Q e =J·E

[0052] Where: J is the total current density vector, Q j,V Let σ be the current volume source, σ be the material conductivity, E be the electric field intensity vector, ρ be the material mass density, and C be the current volume source. p For constant-pressure hot melting of materials, u is the convective velocity, T is the temperature, q is the conduction heat flux vector, and Q is the heat flux vector. e It is a Joule heat source;

[0053] The surface-to-surface radiation mathematical model is as follows:

[0054] J = εe b (T)+ρ d G

[0055] G = G m +G amb +G ext

[0056] G amb =F amb ε amb e b (T amb )

[0057] e b (T)=n 2 σT 4

[0058] -n·q=q r,net ;

[0059] The diffuse reflection condition is as follows:

[0060] ε+ρ d =1,G amb =F amb e b (T amb ), G ext =q s q r,net =ε(Ge b (T));

[0061] In the formula: J is emissivity, ε is surface emissivity, and e b (T) is the radiated power at all wavelengths, ρ d G is the diffuse reflectance coefficient, G is the irradiance, G m For mutual irradiance, G amb G represents the irradiance of environmental radiation. ext F represents the irradiance of an external radiation source. amb As a perspective factor, ε amb For environmental emissivity, T amb It is in F amb The assumed far-end temperature in the included direction, n is the refractive index, and σ = 5.67 × 10⁻⁶. -8 W / (m 2 ·K 4 ) represents the Stefan-Boltzmann constant; q s For external heat flux, q r,net Net radiative heat flux;

[0062] The mathematical model of the electrostatic field is as follows:

[0063]

[0064] In the formula: D is the electric displacement vector, ρ q For the space charge density, ε0 ​​= 8.854187817 × 10 -12 F / m, ε r The relative permittivity of the material;

[0065] The mathematical model for the motion of charged particles in the electric field is as follows:

[0066]

[0067]

[0068] F e =eZE

[0069]

[0070] In the formula: q is the position vector, F e For the electric field force, e = 1.602176634 × 10 -19C is the elementary charge; Z is the charge number, m p For the mass of the electron motion, m r =9.10938356×10 -31 kg is the rest mass of the electron; v is the velocity of the electron, c = 2.99792458 × 10⁻⁶. 8 m / s is the speed of light in a vacuum.

[0071] Furthermore, after meshing the soft X-ray tube, performing simulation calculations, and obtaining simulation results of the thermionic motion characteristics, the influence of thermionic collisions with the bottom of the vacuum tube on the surface insulation performance is determined by the migration direction of thermionic electrons.

[0072] By analyzing the particle trajectory of the thermionic electron beam, the solid angle and intensity distribution of the transmitted soft X-ray radiation can be determined.

[0073] By observing the differences in the distribution of the transmission current density generated by thermionic electrons, we can determine the angle of thermionic electron emission, its distribution on the target electrode, and the transmission current density, thereby determining the differences in the power dissipation capacity and the uniformity of the power dissipation performance within the radiation space.

[0074] By assessing the probability of thermionic transmission, we can determine the thermionic emission utilization efficiency and the soft X-ray emission efficiency or soft X-ray emission effectiveness, thereby judging the degree of improvement in electrostatic elimination efficiency.

[0075] By comparing the change in the average kinetic energy of thermionic electrons over time, we can determine the efficiency of the thermionic electrons' electric field energy utilization and the time it takes for the device to reach a stable working state after startup. By comparing the magnitude of the average kinetic energy of electrons, we can compare the stability of the soft X-ray emission direction of different soft X-ray tubes, the stability of the uniform spatial distribution of ionized positive and negative ions, and the stability of the ability to dissipate charge on charged objects at different angles.

[0076] Compared with the prior art, the advantages of the present invention are:

[0077] 1. The technical solution of the present invention adopts a matching structure mode in which the emitting cathode and the target electrode are set at the same center point. That is, the thermionic emitting surface, the internal target surface (tungsten coating) for thermionic impact, and the transmission surface (beryllium window) are concentric spherical surfaces. Thermionic electrons will be uniformly dispersed and perpendicularly impact the internal target surface (i.e., the transmission absorption distance is the same), so that the energy distribution of the transmitted soft X-rays is more concentrated (i.e., the energy value is more consistent) and the spatial distribution is more uniform. This makes the spatial distribution of the ionized positive and negative ions more uniform (i.e., the ion number density at each spatial position is more consistent). In this way, the uniformity of the ability to eliminate charge on charged objects at different angles within the radiation solid angle can be achieved.

[0078] 2. The technical solution of the present invention utilizes the matching structure of setting the emitting cathode and the target electrode at the same center point to form a radial spatial electric field between them. Thermionic electrons will radially impact the internal target surface, thus forming a large soft X-ray three-dimensional radiation angle, thereby achieving a significant improvement in the power elimination range (determined by its three-dimensional radiation angle).

[0079] 3. The technical solution of the present invention adopts a spherical cap-shaped anode target structure, which allows the sputtered metal particles generated after high-speed hot electrons collide with the target electrode to remain in the "concave" structure of the spherical cap-shaped anode target. This avoids the disadvantage that sputtered metal particles would adhere to the inner surface of the vacuum tube due to the sputtering of metal on the target electrode surface, which would reduce the insulation performance of the vacuum tube surface and cause electrical breakdown of the inner surface of the vacuum tube.

[0080] 4. The technical solution of the present invention adopts a spherical cap-shaped confined electrode mode, which enables the hot electrons to move in a controlled manner toward the spherical cap-shaped anode target, effectively avoiding the hot electron spillover caused by the circular tube-shaped focusing electrode in the prior art, thereby improving the hot electron emission utilization efficiency, and thus improving the soft X-ray emission efficiency (or effectiveness), and also improving the electrostatic elimination efficiency (effectiveness); at the same time, it effectively avoids the material surface sputtering caused by the hot electrons colliding with the bottom of the vacuum tube, which leads to a reduction in surface insulation performance. Attached Figure Description

[0081] Figure 1 A schematic front view of an existing flexible X-ray tube structure;

[0082] Figure 1a A schematic front view of an existing flexible X-ray tube structure with dimensional parameters;

[0083] Figure 1-1 This is a schematic diagram of the existing soft X-ray transmission absorption distance;

[0084] Figure 2 This is a schematic top view of an existing flexible X-ray tube structure;

[0085] Figure 3 Left view of an existing flexible X-ray tube structure;

[0086] Figure 3-1 This is a schematic diagram of the thermal emission cathode structure of an existing flexible X-ray tube;

[0087] Figure 4 A schematic axial view of an existing flexible X-ray tube structure;

[0088] Figure 5 This is a schematic front view of the flexible X-ray tube structure of the present invention;

[0089] Figure 5a A schematic front view of the flexible X-ray tube structure of the present invention with dimensional parameters;

[0090] Figure 6 This is a schematic top view of the flexible X-ray tube structure of the present invention;

[0091] Figure 7 This is a schematic left view of the flexible X-ray tube structure of the present invention;

[0092] Figure 7-1 This is a schematic diagram of the thermal emission cathode structure of the flexible X-ray tube of the present invention;

[0093] Figure 8 This is a schematic axial view of the flexible X-ray tube structure of the present invention;

[0094] Figure 9 This is a flowchart of the simulation and comparison test of the soft X-ray tube electrode structure of the present invention;

[0095] Figure 10-1 A schematic diagram of the temperature field distribution of the cylindrical spiral tungsten filament emitting cathode in an existing soft X-ray tube;

[0096] Figure 10-2 This is a schematic diagram of the temperature field distribution of the spherical spiral tungsten filament emitting cathode in the soft X-ray tube of the present invention;

[0097] Figure 11-1 A front view of the hot electron trajectory distribution in an existing flexible X-ray tube;

[0098] Figure 11-2 A top view of the hot electron trajectory distribution in an existing flexible X-ray tube;

[0099] Figure 11-3 Left view of the hot electron trajectory distribution in an existing flexible X-ray tube;

[0100] Figure 11-4 An axial view of the hot electron trajectory distribution in an existing flexible X-ray tube;

[0101] Figure 11-5 This is a front view of the hot electron trajectory distribution in the flexible X-ray tube of the present invention;

[0102] Figure 11-6 This is a top view of the hot electron trajectory distribution in the flexible X-ray tube of the present invention;

[0103] Figure 11-7 This is a left view of the hot electron trajectory distribution in the flexible X-ray tube of the present invention;

[0104] Figure 11-8 This is an axial view of the hot electron trajectory distribution in the flexible X-ray tube of the present invention;

[0105] Figure 12-1 A schematic diagram of the current density distribution of the target electrode in an existing soft X-ray tube.

[0106] Figure 12-2This is a left view of the current density distribution of the target electrode in the soft X-ray tube of the present invention.

[0107] Figure 12-3 This is a top view of the current density distribution of the target electrode in the soft X-ray tube of the present invention.

[0108] Figure 12-4 This is a front view of the current density distribution of the target electrode in the soft X-ray tube of the present invention.

[0109] Figure 13 This is a comparison chart of the hot electron transport probability of existing flexible X-ray tubes with that of the present invention;

[0110] Figure 14 This is a comparison chart of the average kinetic energy of hot electrons in existing flexible X-ray tubes and that of the present invention.

[0111] Figure 15 This is a comparison chart of the target surface transmission current of existing soft X-ray tubes with that of the present invention;

[0112] In the figure, 1 is the cylindrical spiral tungsten filament emitting cathode of the existing flexible X-ray tube, 1-1 is the metal lead, 2 is the circular planar anode target of the existing flexible X-ray tube, 2-0 is the hot electron motion trajectory, 2-1 is the tungsten coating, 2-2 is the beryllium window, 2-2-1 is the soft X-ray transmission absorption distance (h is equal to the beryllium window thickness, d1 and d2 are greater than the beryllium window thickness, d1 is greater than d2), 3 is the focusing electrode of the existing flexible X-ray tube, 3-1 is the metal lead, 4 is the vacuum tube body, and 4-1 is the bottom cover of the vacuum tube.

[0113] 1' is the spherical spiral tungsten filament emitting cathode of the present invention, 1-1' is the first pair of metal leads, 2' is the spherical cap-shaped anode target of the present invention, 3' is the spherical cap-shaped confinement electrode of the present invention, 3-1' is the second pair of metal leads, 3-2' is the through hole for the metal leads of the spherical cap-shaped confinement electrode, 4' is the vacuum tube body, 4-1' is the bottom cover plate of the vacuum tube, and 5 is soft X-ray. Detailed Implementation

[0114] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0115] 1. See Figure 5 , Figure 5a and combined Figure 7-1 As shown, a spherical spiral tungsten filament emitting cathode 1' is set up, and its specific structural parameters conform to the following expression in the Cartesian coordinate system:

[0116] x=2.5×sin(s×180)×cos(s×360×15)

[0117] y=2.5×sin(s×180)×sin(s×360×15)

[0118] z = 2.5 × cos(s × 180)

[0119] Where s takes the value (0, 1×(2×pi)×0.003); the above expression parameters are the parameters set for this technical solution, and other parameter values ​​can also be set according to design needs.

[0120] The spherical spiral tungsten filament cathode 1' is used to emit thermionic electrons.

[0121] 2. A spherical cap-shaped anode beryllium target 2' is set up. The inner surface (concave surface) of the target electrode is uniformly coated with a tungsten coating (not shown in the figure). The center point of the target electrode is located at the center point of the spherical spiral tungsten filament emitting cathode 1'. It is used to receive the high-speed thermionic electrons emitted by the spherical spiral tungsten filament emitting cathode 1', and to generate soft X-rays using the tungsten coating, which are then transmitted through the beryllium window to form external radiation.

[0122] 3. A spherical cap-shaped confinement electrode 3' is set, the center of which is also located at the center of the spherical spiral tungsten filament emitting cathode 1'. The function of the spherical cap-shaped confinement electrode 3' is to confine the thermionic electrons to move backward, effectively preventing the thermionic electrons from sputtering to the bottom area of ​​the ceramic vacuum tube, so as to maintain the insulation performance of the vacuum tube surface. Thus, the spherical spiral tungsten filament emitting cathode 1', the spherical cap-shaped anode beryllium target 2', and the spherical cap-shaped confinement electrode 3' together constitute a directionally controlled radial thermionic emission electrode structure.

[0123] 4. See Figure 5 , Figure 5a , Figure 6 As shown, the two ends of the spherical spiral tungsten filament emitting cathode 1' are brazed to two first pair of metal leads 1-1', while the two ends of the spherical crown-shaped binding electrode 3' are brazed to two second pair of metal leads 3-2'. The two metal leads constituting the first pair of metal leads and the two metal leads constituting the second pair of metal leads are structurally isolated from each other, orthogonally arranged, and are both fixedly welded to the bottom cover plate 4-1' of the ceramic vacuum tube 4'.

[0124] 5. See Figure 5 , Figure 5a , Figure 8 As shown, a spherical cap-shaped beryllium anode target 2' coated with tungsten is brazed to the top (or front end) of a ceramic vacuum tube 4'.

[0125] 6. Among them, see Figure 6 , Figure 7As shown, the aforementioned spherical cap-shaped confinement electrode 3' is provided with a pair of through holes 3-2', which allow the first pair of metal leads 1-1' of the fixed spherical spiral tungsten filament emitting cathode 1' to pass through, so as to braze them onto the bottom cover plate 4-1' of the ceramic vacuum tube. The radial dimension of the through holes 3-2' is slightly larger than the diameter of the first pair of metal leads 1-1', so that the spherical spiral tungsten filament emitting cathode 1' and the spherical cap-shaped confinement electrode 3' are electrically insulated from each other.

[0126] To verify the rationality of the flexible X-ray tube structure of this technical solution, simulation experiments were conducted on the flexible X-ray tube structures of existing technologies and the flexible X-ray tube structure of this technical solution. The method and procedure of the comparative experiment are as follows:

[0127] Models of the electrode structures of existing soft X-ray tubes and the soft X-ray tube electrode structure of this technical solution are constructed respectively. First, a mathematical model of electromagnetic (Joule) heat transfer and surface-to-surface radiation is applied to the soft X-ray tube, a physical mesh is divided, and simulation calculations are performed to obtain the thermal field distribution of the soft X-ray tube, especially the thermal emission cathode, which provides a thermal field distribution data basis for further simulation of thermionic motion.

[0128] Furthermore, an electrostatic field mathematical model is applied to the flexible X-ray tube, and a mathematical model of charged particle motion in an electric field is applied to the vacuum space inside the flexible X-ray tube. The temperature field distribution of the thermionic emission boundary condition must be obtained using data from thermal field simulation.

[0129] The flexible X-ray tube was meshed, and simulation calculations were performed to obtain simulation results of the thermionic motion characteristics. The displacement, energy, and transport current characteristics of thermionic motion presented by different flexible X-ray tube structures were analyzed and compared.

[0130] Finally, by analyzing the thermionic electron transport probability to the target electrode, the average electron kinetic energy, and the magnitude and density distribution of the transport current, a more suitable soft X-ray tube electrode system structure for large stereo radiation angles and uniform radiation intensity was determined. Best embodiment:

[0131] To verify the rationality of the flexible X-ray tube structure in this technical solution, simulation experiments were conducted comparing the existing flexible X-ray tube structure with the flexible X-ray tube structure of this technical solution. Figure 9 As shown, the methodology and results analysis of the comparative experiment are as follows:

[0132] 1. See Figures 1 to 8 As shown, electrode structures for existing flexible X-ray tubes and the flexible X-ray tube electrode structure of this technical solution are constructed respectively. It should be noted that the existing flexible X-ray tube is constructed by measuring and simplifying a physical object. Its most important dimensions are shown in [reference needed]. Figure 1a As shown in the figure; while the dimensions of the flexible X-ray tube in this technical solution are shown in the figure. Figure 5a As shown in the image.

[0133] 2. Because thermionic cathode flexible X-ray tubes require the cathode wire to be heated by electricity to a certain temperature before electrons can escape from the metal electrode surface, preparing for electron spatial migration; simultaneously, surface thermal radiation is generated during the electric heating process, causing temperature changes. Therefore, electromagnetic (Joule) heat transfer and surface-to-surface radiation mathematical models are applied to both existing technologies and the flexible X-ray tubes of this technical solution; specifically, the electromagnetic (Joule) heat transfer mathematical model is applied to thermionic cathodes:

[0134]

[0135] J = σE

[0136]

[0137] Q e =J·E

[0138] Where: J is the total current density vector, A / m 2 Q j,V As a volumetric current source, A / m 3 σ is the electrical conductivity of the material, S / m; E is the electric field intensity vector, V / m; ρ is the mass density of the material, kg / m³. 3 C p For constant-pressure hot melting of the material, J / (kg·K); u is the convective velocity, m / s, which is 0 m / s due to the vacuum environment; T is the temperature, K; q is the conduction heat flux vector (heat flux density vector), W / m 2 Q e As a Joule heat source, W / m 3 .

[0139] In this embodiment, the materials used in the soft X-ray tube are simplified as follows: the thermal emission cathode, metal leads, focusing electrode, spherical cap-shaped confinement electrode, and target electrode are made of tungsten, and the vacuum tube body is made of alumina; relevant material characteristic parameters can be found in literature.

[0140] The boundary conditions for electromagnetic (Joule) heat transfer are:

[0141] 1) Electrical insulation of the hot cathode surface: n·J=0;

[0142] 2) One end of the hot cathode metal lead (1-1, 1-1') is grounded: V = 0V;

[0143] 3) The input power at the other end of the hot cathode metal leads (1-1, 1-1') is set to: P0 = 1.22W / 0.0586W, so as to achieve the same or similar maximum temperature of the hot emission cathode;

[0144] 4) Heat flux on the outer surface of the flexible X-ray tube: -n·q=q0, q0=h(T)ext -T);

[0145] Wherein: the heat transfer coefficient is set to h = 5 W·m -2 ·k -1 q0 is the inward heat flux density, perpendicular to the boundary, in W / m 2 The external temperature is set to T. ext =293.15K.

[0146] Specifically, a surface-to-surface radiation mathematical model is applied to the outer surface of a soft X-ray tube:

[0147] J = εe b (T)+ρ d G

[0148] G = G m +G amb +G ext

[0149] G amb =F amb ε amb e b (T amb )

[0150] e b (T)=n 2 σT 4

[0151] -n·q=q r,net Inward heat flux (surface radiation heat transfer);

[0152] The diffuse reflection condition is as follows:

[0153] ε+ρ d =1,G amb =F amb e b (T amb ), G ext =q s q r,net =ε(Ge b (T))

[0154] In the formula: J is the radiance, W / m 2 ε is the surface emissivity (SI unit is 1), a dimensionless number in the range 0 ≤ ε ≤ 1. b (T) is the radiated power at all wavelengths, W / m 2 It depends on the fourth power of the temperature; ρ d G is the diffuse reflectance coefficient; G is the irradiance, W / m². 2 G m Mutual irradiance, W / m 2 Gamb The irradiance of the environment is expressed in W / m². 2 G ext Irradiance of the external radiation source, W / m 2 ;F amb As a perspective factor, it is a range of 0 ≤ F amb A dimensionless number ≤ 1. ε amb The ambient emissivity (SI unit is 1) is a value in the range 0 ≤ ε. amb Dimensionless numbers ≤ 1; T amb It is in F amb The assumed far-end temperature (SI unit: K) is included in the direction. n is the refractive index (SI unit: 1); σ = 5.67 × 10⁻⁶ -8 W / (m 2 ·K 4 ) represents the Stefan-Boltzmann constant; q s External heat flux, W / m 2 ;q r,net Net radiative heat flux, W / m 2 In this case, the ambient radiation is set as blackbody radiation, and the ambient temperature is set as T. amb =293.15[K], using the half-cube radiation method.

[0155] 3. Divide the physical mesh, perform simulation calculations, and obtain the thermal field distribution of the soft X-ray tube, especially the thermal emission cathode (1, 1'), to provide thermal field distribution data for further simulation of thermionic motion.

[0156] 4. See Figure 10-1 , Figure 10-2 The figures show the thermal field (temperature) distribution of the thermal emission cathode (1, 1') of the soft X-ray tube in the prior art and the present technical solution, respectively.

[0157] 5. After obtaining the thermal field (temperature) distribution results of the thermionic cathode (1, 1') of the flexible X-ray tube, apply electrostatic field mathematical models to the flexible X-ray tubes of existing technologies and this technical solution, and apply mathematical models of charged particle motion in an electric field to the vacuum space inside the flexible X-ray tube; specifically, apply electrostatic field mathematical models to the entire flexible X-ray tube:

[0158]

[0159] In the formula: D is the electric displacement vector, C / m 2 ;ρ q Space charge density, C / m 3 ε0=8.854187817×10 -12 F / m, ε r This is the relative permittivity of the material, which can be found in literature.

[0160] The electrostatic field boundary conditions are as follows:

[0161] 1) Zero charge boundary: n·D=0;

[0162] 2) Apply voltage to the thermal emission cathode (1, 1'), focusing electrode (3), binding electrode (3'), and metal leads (1-1', 3-1'): V = -10000V; or apply a voltage slightly lower than that of the thermal emission cathode (1') to the binding electrode (3') and metal leads (3-1'), such as V = -10500V. This will be more conducive to the migration of hot electrons to the target electrode and will suppress the movement of hot electrons in directions other than the target electrode, thus preventing unnecessary sputtering losses.

[0163] 3) The anode targets (2, 2') are set as grounded electrodes: V = 0V;

[0164] Specifically, mathematical models of charged particle motion in an electric field are applied to the vacuum space inside a soft X-ray tube:

[0165]

[0166] F e =eZE

[0167]

[0168] In the formula: q is the position vector, m; F e The electric field force is N; e = 1.602176634 × 10 -19 C is the elementary charge; Z is the charge number, which is -1 in this example; m p For the mass of an electron in motion, kg; m r =9.10938356×10 -31 kg is the rest mass of the electron; v is the velocity of the electron, m / s; c = 2.99792458 × 10⁻⁶ 8 m / s is the speed of light in a vacuum.

[0169] Among them, the thermionic emission boundary conditions are:

[0170]

[0171] v t1 =vcosθsinφ

[0172] v t2 =vsinθsinφ

[0173] v n =vcosφ

[0174] φ∈[0,2π], U∈[0,1]

[0175] W=-LambertW(-1,(U-1)exp(-1))-1,W=-log(U1U2)

[0176] In the formula: J th Thermionic emission current density, A / m 2 T is the temperature of the thermionic cathode (tungsten wire electrode), in K; Φ is the work function of the metal, in this example the work function of tungsten is 4.55V; A * = 110A / (K·cm) 2 K is the effective Charleson constant; B =1.380649×10 -23 J / K, Boltzmann constant; v n It is the velocity component perpendicular to the cathode surface, v t1 and v t2 These are two orthogonal velocity components parallel to the cathode surface. The azimuth angle φ is uniformly distributed in the interval [0, 2π]; the polar angle is θ, in rad; U is a uniformly distributed random number in the interval [0, 1]; v is the initial electron velocity, in m / s; W is the normalized kinetic energy, which satisfies the product logarithm function; U1 and U2 are mutually uncorrelated uniformly distributed random numbers in (0, 1).

[0177] The temperature data in the above formula for thermionic emission current density must be obtained using data obtained from thermal field simulation.

[0178] 6. Mesh the soft X-ray tube, perform simulation calculations, and obtain simulation results of the hot electron motion characteristics. See [link to simulation results]. Figures 11-1 to 11-8 As shown.

[0179] 7. Comparison Figure 11-1 , 11-2 As can be seen from 11-3, 11-4 and 11-5, 11-6, 11-7, 11-8, the focusing electrode 3 used in existing flexible X-ray tubes mainly serves to focus electrons, but does not completely constrain the migration behavior of thermionic electrons. This results in a large proportion of thermionic electrons colliding with the bottom of the flexible X-ray tube (see the cover plate area / near 4-1). This easily causes sputtering corrosion of the vacuum tube wall material, leading to a decrease in the surface insulation performance of the vacuum tube, and also easily affects the space charge / electric field distribution inside the tube, causing electrical breakdown of the inner surface of the tube. In contrast, the flexible X-ray tube of this technical solution, due to the setting of the spherical cap-shaped confinement electrode 3', ensures that the migration direction of thermionic electrons is almost entirely towards the spherical cap-shaped anode target 2', thus effectively avoiding the decrease in the surface insulation performance of the bottom of the vacuum tube caused by the sputtering of thermionic electrons themselves.

[0180] 8. From Figures 11-1 to 11-8It can also be seen that the existing soft X-ray tube's thermionic beam is relatively more concentrated, and the incident trajectory (trace) presents a significant angle with the target surface. Therefore, the radiation intensity of the transmitted soft X-rays will mainly be concentrated within a small solid radiation angle emanating from the center of the target surface, and the radiation energy at the edges of the solid radiation angle is relatively weak. In contrast, the soft X-ray tube's thermionic beam in this technical solution is more dispersed, with a radial distribution on the target surface, and the incident trajectory (trace) is more perpendicular to the target surface. Therefore, the transmitted soft X-ray radiation solid angle is larger, and the radiation intensity distribution is more uniform. This allows for a more uniform spatial distribution of ionized positive and negative ions (more consistent ion number density at each spatial location), thereby achieving consistency in the de-energizing ability of charged objects at different angles within the radiation solid angle.

[0181] 9. Comparison Figure 12-1 and Figure 12-2 , 12-3 Figure 12-4 also shows the difference in the distribution of the transmission current density generated by thermionic electrons. Compared with the existing soft X-ray tubes, the soft X-ray tube of this technology has a larger thermionic emission angle, a more uniform distribution on the target electrode, and a higher transmission current density. This is more conducive to transmitting soft X-rays with a larger solid angle, greater radiation intensity, and more uniformity. In turn, it is conducive to ionizing positive and negative ions more uniformly and more widely over a wider solid angle range, thereby improving the power dissipation capability and the balance of power dissipation performance in the radiation space.

[0182] 10. See Figure 13 As shown, the hot electron transport probability of the soft X-ray tube in this technical solution is significantly higher than that of the prior art. That is, a larger proportion of hot electrons will collide with the target electrode, which can reduce the directional loss of hot electrons and generate more soft X-rays. This improves the hot electron emission utilization efficiency, thereby improving the soft X-ray emission efficiency (energy) and also improving the electrostatic elimination efficiency (energy).

[0183] 11. See Figure 14 As shown, the average kinetic energy of the thermionic electrons in this technical solution is significantly higher than that of existing technologies, and it reaches a high kinetic energy state in a faster time. This indicates that the thermionic electrons have a higher efficiency in utilizing electric field energy and reach a stable working state more quickly after startup. Furthermore, the higher the electron kinetic energy, the better the forward directionality of the transmitted soft X-rays, and the more consistent they are with the direction of the thermionic electron beam. This improves the stability of the soft X-ray emission direction, thereby improving the stability of the uniform spatial distribution of ionized positive and negative ions, which also means improving the stability of the ability to de-energize charged objects at different angles.

[0184] 12. See Figure 15As shown, the soft X-ray tube of this technical solution has a significantly improved transmission current due to the overall matched electrode structure design and the appropriately increased overall size of the thermal emission cathode. It also reaches a stable state in a faster time. This indicates that more soft X-rays will be generated in a shorter time, which is beneficial for ionizing more positive and negative ions in a short time and improving the immediacy of the elimination.

[0185] In summary, the technical solution of this invention employs a spherical / spherical structure consisting of a spherical spiral emitting cathode, a spherical cap-shaped anode, and a spherical cap-shaped confinement electrode. Furthermore, the concentric spherical structure, with the center points of the spherical spiral emitting cathode, spherical cap-shaped anode, and spherical cap-shaped confinement electrode all aligned at the same center point, can create a larger soft X-ray stereo radiation angle. This ensures consistent electrostatic discharge capability for charged objects at different angles within the radiation stereo angle. It also significantly improves the electrostatic discharge range. Moreover, the use of a spherical cap-shaped anode target structure avoids sputtering and overflow of metal from the target electrode surface, thus improving soft X-ray emission efficiency and electrostatic discharge efficiency.

[0186] This invention can be widely used in the design and manufacture of electrostatic-eliminating flexible X-ray tubes.

Claims

1. A flexible X-ray tube structure for electrostatic elimination, comprising a vacuum tube body, characterized in that: A spherical spiral tungsten filament emission cathode is installed inside the vacuum tube; The spherical spiral tungsten filament emission cathode is a spherical spiral emission cathode formed by a tungsten filament spirally coiled around a sphere with a radius of R1. The spherical spiral tungsten filament emitting cathode is used to emit thermionic electrons; In front of the spherical spiral tungsten filament emitting cathode, a spherical cap-shaped anode beryllium target electrode with an opening facing the spherical spiral tungsten filament emitting cathode is set, and a tungsten coating is uniformly deposited on the inner surface of the spherical cap-shaped anode beryllium target electrode. The aforementioned spherical cap-shaped anode beryllium target electrode has a spherical cap-shaped curved surface with a radius of R2; The aforementioned spherical cap-shaped anode beryllium target electrode is used to receive high-speed thermionic electron impacts emitted by a spherical spiral tungsten filament emitting cathode, and to generate soft X-rays using a tungsten coating, which are then transmitted through a beryllium window to form external radiation. A spherical cap-shaped confinement electrode is placed behind the spherical spiral tungsten filament emitting cathode; The aforementioned spherical cap-shaped binding electrode has a spherical cap-shaped curved surface with a radius of R3; The aforementioned spherical cap-shaped binding electrode is used to constrain the thermionic electrons to move backward, so that the thermionic electrons move in a controlled manner toward the spherical cap-shaped anode target, thereby improving the thermionic electron emission utilization efficiency, improving the soft X-ray emission efficiency, and thus improving the electrostatic elimination efficiency; at the same time, it prevents thermionic electrons from sputtering to the bottom region of the ceramic vacuum tube, avoiding the reduction of the insulation performance of the bottom surface of the vacuum tube caused by the sputtering of the thermionic electrons themselves, so as to maintain the insulation performance of the vacuum tube surface. The spatial positions of the center point of the spherical cap-shaped anode beryllium target electrode, the center point of the spherical cap-shaped binding electrode, and the center point of the spherical spiral tungsten wire emitting cathode coincide; The spherical spiral tungsten filament emitting cathode, the spherical cap-shaped anode beryllium target electrode, and the spherical cap-shaped confinement electrode together constitute a direction-controlled radial thermionic emission electrode structure.

2. The flexible X-ray tube structure for electrostatic elimination according to claim 1, characterized in that: The spherical radius R1 of the spherical spiral tungsten filament emitting cathode is smaller than the radius R3 of the spherical cap-shaped confined electrode. The radius R3 of the spherical cap-shaped confinement electrode is smaller than the radius R2 of the spherical cap-shaped beryllium anode target electrode.

3. The flexible X-ray tube structure for electrostatic elimination according to claim 1, characterized in that: The spherical spiral tungsten filament emitting cathode, the spherical cap-shaped anode beryllium target electrode, and the spherical cap-shaped binding electrode constitute a multi-concentric spherical structure with a common spherical center.

4. The flexible X-ray tube structure for electrostatic elimination according to claim 1, characterized in that: The spherical cap-shaped confinement electrode is disposed inside the vacuum tube and located behind the spherical spiral tungsten filament emitting cathode; The inner surface of the spherical cap-shaped anode beryllium target electrode is a concave surface of a spherical cap-shaped curved surface, and a tungsten coating is uniformly deposited on the concave surface of the spherical cap-shaped curved surface; The spherical cap-shaped anode beryllium target electrode is disposed at the front end of the vacuum tube body, forming a spherical cap-shaped curved protruding beryllium window of the soft X-ray tube.

5. The soft X-ray tube structure for electrostatic elimination according to claim 1, characterized in that... The vacuum tube body is provided with a vacuum tube bottom cover plate at the rear end; Several metal leads are installed through the bottom cover plate of the vacuum tube; The plurality of metal leads include at least two metal leads constituting the first pair of metal leads and two metal leads constituting the second pair of metal leads; The front ends of the first pair of metal leads are electrically connected to the two ends of the spherical spiral tungsten filament emitting cathode, respectively. The front end of the second pair of metal leads is electrically connected to the spherical cap-shaped binding electrode. The spherical spiral tungsten filament emitting cathode and the spherical cap-shaped confined electrode are electrically insulated from each other.

6. The soft X-ray tube structure for electrostatic elimination according to claim 5, characterized in that... On the spherical cap-shaped surface of the spherical cap-shaped binding electrode, a pair of through holes are provided to allow the two metal leads constituting the first pair of metal leads to pass through the spherical cap-shaped surface of the spherical cap-shaped binding electrode in an electrically insulating manner.

7. The flexible X-ray tube structure for electrostatic elimination according to claim 5, characterized in that: The two metal leads that make up the first pair of metal leads are structurally isolated and electrically insulated from the two metal leads that make up the second pair of metal leads; On the bottom cover plate of the vacuum tube, two pairs of metal leads are arranged orthogonally.

8. A method for verifying the soft X-ray tube structure for electrostatic elimination as described in claim 1, characterized in that: The verification method includes: 1) Construct models of the existing soft X-ray tube electrode structure and the soft X-ray tube electrode structure of this technical solution in finite element software or simulation software respectively; 2) For soft X-ray tubes, apply electromagnetic-Joule heat transfer and surface-to-surface radiation mathematical models; 3) Mesh the entire flexible X-ray tube, perform simulation calculations, and obtain the thermal field distribution of the flexible X-ray tube; 4) Applying an electrostatic field mathematical model to flexible X-ray tubes; 5) For the vacuum space inside the soft X-ray tube, apply a mathematical model of charged particle motion in an electric field, where the temperature field distribution of the thermionic emission boundary condition must be obtained from thermal field simulation data. 6) Mesh the soft X-ray tube, perform simulation calculations, and obtain simulation results of the hot electron motion characteristics; 7) Analyze and compare the characteristics of thermionic displacement, energy, and transport current exhibited by different flexible X-ray tube structures; 8) By analyzing the thermionic electron transport probability, average electron kinetic energy, and the magnitude and density distribution of the transport current to the target electrode, a soft X-ray tube electrode system structure that is more suitable for large stereo radiation angles and uniform radiation intensity can be determined.

9. The method for verifying a soft X-ray tube structure for electrostatic elimination according to claim 8, characterized in that: The electromagnetic-Joule heat transfer mathematical model is as follows: J = σE Q e =J·E Where: J is the total current density vector, Q j,V Let σ be the current volume source, σ be the material conductivity, E be the electric field intensity vector, ρ be the material mass density, and C be the current volume source. p For constant-pressure hot melting of materials, u is the convective velocity, T is the temperature, q is the conduction heat flux vector, and Q is the heat flux vector. e It is a Joule heat source; The surface-to-surface radiation mathematical model is as follows: Jsεe b (T)+ρ d G G=G m +G amb +G ext G amb =F amb ε amb e b (T amb ) e b (T)=n 2 σT 4 -n·q=q r,net ; The diffuse reflection condition is as follows: e+r d =1, G amb =F amb e b (T amb ),G ext =q s ,q r,net =ε(Ge b (T)); In the formula: J is emissivity, ε is surface emissivity, and e b (T) is the radiated power at all wavelengths, ρ d G is the diffuse reflectance coefficient, G is the irradiance, G m For mutual irradiance, G amb G represents the irradiance of environmental radiation. ext F represents the irradiance of an external radiation source. amb As a perspective factor, ε amb For environmental emissivity, T amb It is in F amb The assumed far-end temperature in the included direction, n is the refractive index, and σ = 5.67 × 10⁻⁶. -8 W / (m 2 ·K 4 ) represents the Stefan-Boltzmann constant; q s For external heat flux, q r,net Net radiative heat flux; The mathematical model of the electrostatic field is as follows: In the formula: D is the electric displacement vector, ρ q For the space charge density, ε0 ​​= 8.854187817 × 10 -12 F / m, ε r The relative permittivity of the material; The mathematical model for the motion of charged particles in the electric field is as follows: F e =eZE In the formula: q is the position vector, F e For the electric field force, e = 1.602176634 × 10 -19 C is the elementary charge; Z is the charge number, m p For the mass of the electron motion, m r =9.10938356×10 -31 kg is the rest mass of the electron; v is the velocity of the electron, c = 2.99792458 × 10⁻⁶. 8 m / s is the speed of light in a vacuum.

10. The method for verifying a soft X-ray tube structure for electrostatic elimination according to claim 9, characterized in that... After meshing the soft X-ray tube and performing simulation calculations to obtain the simulation results of the hot electron motion characteristics, the influence of material surface sputtering caused by hot electron collisions with the bottom of the vacuum tube on the surface insulation performance is determined by the migration direction of the hot electrons. By analyzing the particle trajectory of the thermionic electron beam, the solid angle and intensity distribution of the transmitted soft X-ray radiation can be determined. By observing the differences in the distribution of the transmission current density generated by thermionic electrons, we can determine the angle of thermionic electron emission, its distribution on the target electrode, and the transmission current density, thereby determining the differences in the power dissipation capacity and the uniformity of the power dissipation performance within the radiation space. By assessing the probability of thermionic transmission, we can determine the thermionic emission utilization efficiency and the soft X-ray emission efficiency or soft X-ray emission effectiveness, thereby judging the degree of improvement in electrostatic elimination efficiency. By comparing the change in the average kinetic energy of thermionic electrons over time, we can determine the electric field energy utilization efficiency of thermionic electrons and the time it takes to reach a stable working state after power-on. By comparing the magnitude of the average kinetic energy of electrons, the stability of the soft X-ray emission direction of different soft X-ray tubes, the stability of the spatial uniform distribution of ionized positive and negative ions, and the stability of the ability to de-energize charged objects at different angles are compared.

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