CN110795865A - CST analog simulation method combined with field emission X-ray tube electron gun - Google Patents
CST analog simulation method combined with field emission X-ray tube electron gun Download PDFInfo
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Abstract
The invention discloses a CST simulation method combined with a field emission X-ray tube electron gun, which belongs to the field of X-ray gun CST simulation. For a high-power X-ray gun, it is necessary to use a three-electrode structure with a beam-focusing electrode, which can form a focused electric field with the anode, so that the electrons can completely pass through the anode hole after being focused. The two-electrode X-ray gun is only suitable for small power applications, where unfocused electron beams bombard the anode to melt the anode.
Description
Technical Field
The invention relates to the field of CST analog simulation of an X-ray gun, in particular to a CST analog simulation method combined with a field emission X-ray tube electron gun.
Background
The development of the electron beam melting technology shows that the technology with application value can be developed at a high speed, and the technology related to practical application can be developed. Without practical production applications, electron beam melting technology has not been stopped for a considerable period of time. After 50 years, the requirements of the processing industry, particularly the military industry, on new material processing are scheduled, and the electron beam welding and smelting technology is mature in tens of years; for the simulation of electron motion, few people study in China, and most study the motion situation of single electron or group electron, or use 2D software to simulate electron beam, the simulated electron trajectory moves in a plane, which is not in line with the actual situation that electron spirally advances in space.
The conventional CST simulation method combined with a field emission X-ray tube electron gun cannot intuitively simulate the motion condition of an electron trajectory in a 3D state.
Disclosure of Invention
The invention aims to solve the problem that the motion condition of an electron track in a 3D state cannot be intuitively simulated, and provides a CST simulation method combined with a field emission X-ray tube electron gun.
In order to achieve the purpose, the invention adopts the following technical scheme:
the CST analog simulation method combined with the field emission X-ray tube electron gun comprises the following steps:
s1, calculating the required slow wave voltage U, electron beam current I and beam waist radius r according to beam interactionw；
S2, according to the calculated data and the required electron beam shape in S1, selecting the structure type of the X-ray gun which can reach the calculated data and the electron beam in S1;
s3, adopting a comprehensive method to calculate and determine main parameters of the X-ray gun and determine an initial value of the X-ray gun;
s4, selecting a model material by CST electromagnetic simulation software according to the material parameters of the X-ray gun;
s5, setting a cathode, an anode and a bunching electrode, and setting boundary conditions and excitation adding conditions;
and S7, simulating the static simulation, the static magnetic simulation and the ion solver in the CST, and optimizing the X-ray gun according to the CST simulation result.
Preferably, the slow wave voltage U in S1 is 32000-wIs 7.5-8.5 mm.
Preferably, the main parameters of the X-ray gun in S3 include conductivity, area compression ratio and range, wherein the conductivity is calculated by using the following formula:
in the above formula UaFor the anode potential, the area compression ratio is calculated using the following formula:
wherein is JmAverage current density, JkThe cathode emission average density, where range refers to the distance between the electron gun cathode and the injection waist, is generally the larger the better, allowing the electron beam to enter the focal field active region with optimal injection conditions.
Preferably, the X-ray gun structure type in S2 adopts an axially symmetric X-ray gun.
Preferably, the cathode material of the X-ray gun in S4 is tantalum, and the rest of the position material is PEC.
Preferably, the cathode in the CST adopts a bulk cathode as an excitation source, and the bulk cathode is made of tantalum bulk; the cubic negative pole left side is concave sphere circle piece, and the round hole has been seted up at the fast center of concave sphere surface element, the round hole is provided with the ion collector behind one's back.
Preferably, a tapered hole is formed in the middle of the beam bunching electrode, the beam bunching electrode is nested with the cathode, the default distance is 1mm, the beam bunching electrode and the cathode have the same potential, and the distance between the beam bunching electrode and the anode meets the requirement of voltage resistance.
Preferably, the anode and the primary focusing framework are designed integrally, a frustum is arranged at the front end of the anode, and a groove is formed in the rear portion of the anode and used for fixing the focusing coil.
Preferably, the boundary condition in the CST is set to open state.
Preferably, the excitation condition in the CST adopts a voltage of 35000V, and the final energy loss of the electron beam is 10%.
Preferably, the simulation of electrostatic simulation, magnetostatic simulation and ion solver in the CST comprises the steps of:
a1, in static field
On the basis of the discrete Faraday's law and the corresponding divergence equation, a linear equation set for solving the electrostatic problem is established:
the solver module can adopt hexahedral meshes or tetragonal meshes; establishing a vector field hi：
By means of the vector field and the scalar bit, and using the following equations, the true magnetic field vector value is obtained:
a2, based on Helmholtz eigenequation, is used for solving passive and lossless time harmonic problem; solutions to the lossless problem are obtained by the kryloff subspace or the jacobian davison method:
a3, based on Lorentz force law in discrete form, solving the effect of electromagnetic field on the movement of charged ions:
a4, based on the previous particle tracking, calculates the corresponding space charge field due to the particle, then calculates the electric field due to the space charge and applies it to the next particle tracking iteration, and the system will iterate over the calculations until the results converge.
Compared with the prior art, the CST analog simulation method combined with the field emission X-ray tube electron gun has the following beneficial effects:
1. the invention carries out comprehensive research on the electron beam forming system of the high-power X-ray gun, simulates the influence of the change of each parameter of the system on the performance of the electron beam, and optimizes the change to obtain an ideal X-ray gun model with practical application value.
Drawings
FIG. 1 is a radial electric field distribution diagram of a CST simulation method combined with a field emission X-ray tube electron gun according to the present invention at a distance of 12 mm;
FIG. 2 is a radial electric field distribution diagram of the CST simulation method combined with the field emission X-ray tube electron gun according to the present invention when the distance is 9 mm;
FIG. 3 is a radial electric field distribution diagram with outer edge of CST simulation method combined with field emission X-ray tube electron gun according to the present invention;
FIG. 4 is a radial electric field distribution diagram without outer edge of the CST simulation method combined with the electron gun of the field emission X-ray tube according to the present invention;
FIG. 5 is a radial electric field distribution diagram of a CST simulation method combined with a field emission X-ray tube electron gun according to the present invention, where the gap between the die hole and the block cathode is 1 mm;
FIG. 6 is a radial electric field distribution diagram of a CST simulation method combined with a field emission X-ray tube electron gun according to the present invention, wherein the gap between the die hole and the block cathode is 2 mm;
FIG. 7 is a radial electric field distribution diagram of a CST simulation method combined with a field emission X-ray tube electron gun according to the present invention when the gap between the die hole and the block cathode is 4 mm.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.
Example 1:
the CST analog simulation method combined with the field emission X-ray tube electron gun comprises the following steps:
s1, calculating the required slow wave voltage U, electron beam current I and beam waist radius r according to beam interactionw；
S2, according to the calculated data and the required electron beam shape in S1, selecting the structure type of the X-ray gun which can reach the calculated data and the electron beam in S1;
s3, calculating and determining main parameters of the X-ray gun, and determining an initial value of the X-ray gun;
s4, selecting a model material by CST electromagnetic simulation software according to the material parameters of the X-ray gun;
s5, setting a cathode, an anode and a bunching electrode, and setting boundary conditions and excitation adding conditions;
and S7, simulating the static simulation, the static magnetic simulation and the ion solver in the CST, and optimizing the X-ray gun according to the CST simulation result.
Further, it is preferable that the slow wave voltage U in S1 is 32000-wIs 7.5-8.5 mm.
Further, it is preferable that the main parameters of the X-ray gun in S3 include conductivity, area compression ratio and range, wherein the conductivity is calculated using the following formula:
in the above formula UaFor the anode potential, the area compression ratio is calculated using the following formula:
wherein is JmAverage current density, JkThe cathode emission average density, where range refers to the distance between the electron gun cathode and the injection waist, is generally the larger the better, allowing the electron beam to enter the focal field active region with optimal injection conditions.
Further, it is preferable that the X-ray gun structure type in S2 employs an X-ray gun of an axisymmetric structure.
Further, it is preferable that the cathode material of the X-ray gun in S4 is tantalum, and the rest of the site material is PEC.
Further, preferably, the cathode in the CST adopts a bulk cathode as an excitation source, and the bulk cathode is made of tantalum bulk; the left side of the blocky cathode is a concave spherical round block, a round hole is formed in the center of the concave spherical surface element, and an ion collector is arranged behind the round hole.
Further, preferably, a tapered hole is formed in the middle of the bunching electrode, the bunching electrode is nested with the cathode, the default distance is 1mm, the bunching electrode and the cathode have the same potential, and the distance between the bunching electrode and the anode meets the requirement of voltage resistance.
Further, preferably, the anode and the primary focusing framework are designed integrally, a frustum is arranged at the front end of the anode, and a groove is formed in the rear portion of the anode and used for fixing the focusing coil.
Further, it is preferable that the boundary condition in the CST is set to the open state.
Further, preferably, the excitation condition in the CST employs a voltage of 35000V, and the final energy loss of the electron beam is 10%.
Further, preferably, the simulation of electrostatic simulation, magnetostatic simulation and ion solver in the CST includes the steps of:
a1, in static field
On the basis of the discrete Faraday's law and the corresponding divergence equation, a linear equation set for solving the electrostatic problem is established:
the solver module can adopt hexahedral meshes or tetragonal meshes; establishing a vector field hi：
By means of the vector field and the scalar bit, and using the following equations, the true magnetic field vector value is obtained:
a2, based on Helmholtz eigenequation, is used for solving passive and lossless time harmonic problem; solutions to the lossless problem are obtained by the kryloff subspace or the jacobian davison method:
a3, based on Lorentz force law in discrete form, solving the effect of electromagnetic field on the movement of charged ions:
a4, based on the previous particle tracking, calculates the corresponding space charge field due to the particle, then calculates the electric field due to the space charge and applies it to the next particle tracking iteration, and the system will iterate over the calculations until the results converge.
Example 2: based on example 1, but with the difference that:
fig. 1-2 show the electron beam trajectory and radial electric field distribution at 12mm and 9mm distances between the cathode and anode, respectively. As can be seen from the simulation, as the distance between the block cathode and the anode decreases, the radial electric field gradually extends outward, and the convergence effect of electrons decreases; however, the electron confinement force by the peripheral electric field is enhanced, and the stability of the formed electron beam is improved.
Example 3: based on examples 1 and 2, but with the difference that:
as can be seen from fig. 3-4, the radial electric field intensity at the inner side is increased significantly when the outer edge is eliminated, which results in enhanced electron convergence and reduced electron beam forming stability. Month _ is more easily deformed by sputtering due to the sharp edges, so the flat outer edge of the block cathode is not eliminated in the design.
Example 4: based on examples 1, 2 and 3, but with the difference that:
the smaller of the beam spot apertures, also referred to as the mode aperture of the beam spot, is of significant value in the design of the X-ray gun. For a block-shaped cathode emission surface with a concave spherical surface, it is difficult to accurately calculate the electric field on the surface of the cathode. Experiments prove that when the potential of the bunching electrode is the same as that of the block cathode, the maximum emission area of the cathode is equal to the area of the bunching electrode die hole. That is, at a given cutoff voltage, the amount of cathode emission surface area is related only to the spot size die diameter and spot voltage. In order to simplify the structure of the X-ray gun, the beam-converging pole and the block cathode of the X-ray gun are not adjusted in the same potential. As can be seen from fig. 5 to 7, the convergence of the free electrons is greatly affected, and the smaller the gap between the die hole and the bulk cathode, the better the convergence of the electrons. But the smaller the orifice diameter is not the better. Too small a gap can increase the difficulty of machining and assembly. Because the electron convergence degree is too high, a beam waist is formed before primary focusing, and a larger pulsation amplitude is formed, so that the stability of the electron beam is reduced, and the rigidity is reduced.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. The CST analog simulation equipment system combined with the field emission X-ray tube electron gun is characterized in that the realization method comprises the following steps:
s1, calculating the required slow wave voltage U, electron beam current I and beam waist radius r according to beam interactionw；
S2, according to the calculated data and the required electron beam shape in S1, selecting the structure type of the X-ray gun which can reach the calculated data and the electron beam in S1;
s3, calculating and determining main parameters of the X-ray gun, and determining an initial value of the X-ray gun;
s4, selecting a model material by CST electromagnetic simulation software according to the material parameters of the X-ray gun;
s5, setting a cathode, an anode and a bunching electrode, and setting boundary conditions and excitation adding conditions;
and S7, simulating the static simulation, the static magnetic simulation and the ion solver in the CST, and optimizing the X-ray gun according to the CST simulation result.
2. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the slow wave voltage U in S1 is 32000-38000V, the electron current I is 6.35-6.85A and the waist radius rwIs 7.5-8.5 mm.
3. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the main parameters of the X-ray gun in the S3 include conductivity, area compression ratio and range, wherein the conductivity is calculated by using the following formula:
in the above formula UaFor the anode potential, the area compression ratio is calculated using the following formula:
wherein is JmAverage current density, JkThe cathode emission average density, where range refers to the distance between the electron gun cathode and the injection waist, is generally the larger the better, allowing the electron beam to enter the focal field active region with optimal injection conditions.
4. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the X-ray gun structure type in the S2 adopts an X-ray gun with an axisymmetric structure.
5. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the cathode material of the X-ray gun in the S4 adopts tantalum, and the rest position material adopts PEC.
6. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the cathode in the CST adopts a blocky cathode as an excitation source, and the blocky cathode is made of tantalum blocks; the cubic negative pole left side is concave sphere circle piece, and the round hole has been seted up at the fast center of concave sphere surface element, the round hole is provided with the ion collector behind one's back.
7. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the middle of the beam bunching electrode is provided with a tapered hole, the beam bunching electrode is nested with the cathode, the default distance is 1mm, the beam bunching electrode and the cathode have the same potential, and the distance between the beam bunching electrode and the anode meets the pressure-resistant requirement.
8. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the anode and the primary focusing framework are designed integrally, a frustum is arranged at the front end of the anode, and a groove is formed in the rear portion of the anode and used for fixing the focusing coil.
9. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the boundary condition in CST is set to open state.
10. The CST analog simulation equipment system combined with field emission X-ray tube electron gun of claim 1, wherein: the simulation of the electrostatic simulation, the magnetostatic simulation and the ion solver in the CST comprises the following steps:
a1, in static fieldOn the basis of the discrete Faraday's law and the corresponding divergence equation, a linear equation set for solving the electrostatic problem is established:
the solver module can adopt hexahedral meshes or tetragonal meshes; establishing a vector field hi：
By means of the vector field and the scalar bit, and using the following equations, the true magnetic field vector value is obtained:
a2, based on Helmholtz eigenequation, is used for solving passive and lossless time harmonic problem; solutions to the lossless problem are obtained by the kryloff subspace or the jacobian davison method:
a3, based on Lorentz force law in discrete form, solving the effect of electromagnetic field on the movement of charged ions:
a4, based on the previous particle tracking, calculates the corresponding space charge field due to the particle, then calculates the electric field due to the space charge and applies it to the next particle tracking iteration, and the system will iterate over the calculations until the results converge.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111312570A (en) * | 2020-03-02 | 2020-06-19 | 电子科技大学 | Simulation method for determining assembly distance between cathode of electron gun and hot wire |
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| US6373178B1 (en) * | 1999-01-12 | 2002-04-16 | Lg Electronics Inc. | Electron gun for color cathode ray tube |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6373178B1 (en) * | 1999-01-12 | 2002-04-16 | Lg Electronics Inc. | Electron gun for color cathode ray tube |
| CN106777552A (en) * | 2016-11-29 | 2017-05-31 | 电子科技大学 | A kind of thermally matched Optimization Design of energy coupler |
| CN109190163A (en) * | 2018-07-30 | 2019-01-11 | 电子科技大学 | A kind of traveling wave tube electron gun design method based on multi-objective optimization algorithm |
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| 杨作为: "行波管电子枪的优化设计", 《中国优秀硕士学位论文全文数据库工程科技Ⅰ辑（月刊 ）》 * |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111312570A (en) * | 2020-03-02 | 2020-06-19 | 电子科技大学 | Simulation method for determining assembly distance between cathode of electron gun and hot wire |
| CN111312570B (en) * | 2020-03-02 | 2021-04-30 | 电子科技大学 | Simulation method for determining assembly distance between cathode of electron gun and hot wire |
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Application publication date: 20200214 |