CN102567780A - Space microwave component low pressure discharge value simulation method - Google Patents
Space microwave component low pressure discharge value simulation method Download PDFInfo
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- CN102567780A CN102567780A CN2011104609250A CN201110460925A CN102567780A CN 102567780 A CN102567780 A CN 102567780A CN 2011104609250 A CN2011104609250 A CN 2011104609250A CN 201110460925 A CN201110460925 A CN 201110460925A CN 102567780 A CN102567780 A CN 102567780A
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Abstract
The invention relates to a space microwave component low discharge value simulation method, which includes steps as follows: establishing a low pressure discharge numerical model of a space microwave component, performing accurate numerical analysis aiming at the motion process of discharged particles during low pressure discharge as well as the total discharged particle number, and obtaining the low pressure discharge threshold value of the space microwave component. According to the invention, the second electron multiplication effect on a metal surface of a space microwave component is taken into consideration, and the discharge threshold value of an intersected stage under a low pressure environment and between the discharge under a vacuum environment and the discharge under a high pressure environment can be analyzed. Meanwhile, all collision types dominating an air space in the microwave component are taken into consideration and the accuracy of the low pressure discharge numerical simulation method in the space microwave component is ensured. Through the method, repeated tests for obtaining the low pressure discharge threshold value of the space microwave component are avoided, the design period is shortened, the preparation cost is reduced, and the method is extremely suitable for analyzing the numerical part of the low pressure discharge in the space microwave component.
Description
Technical field
The present invention relates to a kind of Space Microwave parts low pressure discharge method for numerical simulation, belong to Space Microwave part reliability studying technological domain.
Background technology
There is the risk that low pressure discharge takes place in the spacecraft microwave component from launching the back to the injection duration of work.After the injection, the Space Microwave parts work long hours under high-power condition, and part interior accumulation gas also might cause low pressure discharge.In addition, along with the propelling step by step of China's manned space flight and survey of deep space plan, also might receive the harm of low pressure discharge in the process of spacecraft celestial body outside reentrying or landing.And large aerospace equipment such as dirigible also have the risk that low pressure discharge takes place because of its working environment.Nowadays; The wideer bandwidth of applied Space Microwave part requirement in the spacecraft useful load; Higher element integrated level and bigger power capacity, this must cause having higher electric field density and littler gap size in the Space Microwave parts, and this has also strengthened the risk of low pressure discharge.At present; The low pressure discharge threshold value of Space Microwave parts mainly obtains through testing repeatedly both at home and abroad; Experimental period is long, design cost is high, but and single to the Forecasting Methodology analysis component structure of Space Microwave parts low pressure discharge threshold value, computational accuracy is not high.
In the world at present half analytic formula estimation low pressure discharge threshold values that adopt and test of many times data fitting theoretical based on classical gas breakdown more; The limitation of this method is that equivalent length in the formula only for limited structure, just separates like parallel flat, rectangular waveguide and circular waveguide.European Space Agency has developed all-wave Electromagnetic Simulation instrument (FEST3D) and corona discharge electronic simulation (CEST) to the discharge process that takes place in the hypobaric.FEST3D adopts method of moment to calculate the inner electromagnetic field distribution of microwave component; The hypothesis uniform electromagnetic field distributes in subrange; Calculate the low pressure discharge threshold value through analytic method; This software is applicable to when air pressure is higher that discharge threshold in the microwave component calculates, and only can analysis classes be similar to the structure of rectangular waveguide, and the scope of application is narrower.CEST adopts the hybrid analog-digital simulation method of approximation, considers the interaction of electronics and electromagnetic field, utilizes differential equation.This software can only be analyzed rectangular waveguide, and the numerical simulation of low pressure discharge is also rested on the exploratory stage.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiency of prior art, proposed a kind of Space Microwave parts low pressure discharge method for numerical simulation.
Technical solution of the present invention is:
A kind of Space Microwave parts low pressure discharge method for numerical simulation, the particle of said Space Microwave part interior comprises primary and intended particle, and primary is divided into initiating electron and initial ion by its charging property, and step is following:
(1) set up low pressure discharge numerical model in the Space Microwave parts based on the method for particle simulation, specifically pass through following steps:
(1.1) according to i primary in preset time step Δ t; Judge from the displacement that an initial position moves to another position whether this primary bumps with Space Microwave parts inside surface metal boundary; If the primary displacement of in Δ t, moving more than or equal to its initial position to the distance of metal boundary; Then bump, get into step (1.2); If the primary displacement of in Δ t, moving, does not then bump to the distance of metal boundary less than its initial position, get into step (1.3);
(1.2) judge whether to take place the secondary electron multiplication according to the initial kinetic energy of i primary and the secondary electron emission characteristic of microwave component inside surface metal material; If taking place, the secondary electron multiplication produces secondary electron; Then regard the secondary electron of launching as new particle; Original state with their kinetic energy and displacement is made as next time step gets into step (2) afterwards; If the secondary electron multiplication does not take place, thinks that then i primary absorbed by metal material;
(1.3) judge whether primary bumps with intended particle in the Space Microwave part interior gas space, if R is arranged
1＜P
iSet up, think that then primary collision has taken place for i primary and intended particle, get into step (1.4) afterwards, otherwise think and do not bump, i primary continuation moved, and gets back to step (1.1); Wherein, R
1Be a random number and R
1∈ (0,1), P
iFor total collision probability and P is arranged
i=1-exp (σ
T(ε
i) n
i(x
i) v
iΔ t), v
iBe the initial velocity of i primary, n
t(x
i) be the density of i primary position intended particle, σ
T(ε
i) be total collision cross-section and σ is arranged
T(ε
i)=σ
1(ε
i)+σ
2(ε
i)+σ
3(ε
i)+σ
4(ε
i)+σ
5(ε
i)+σ
6(ε
i), σ
1(ε
i), σ
2(ε
i) ... σ
6(ε
i) be the collision cross-section of contingent 6 kinds of collisions between i primary and the intended particle, the acquisition of can tabling look-up;
Wherein, σ
1Be the collision cross-section of elastic collision between electronics and the neutral atom, σ
2The collision cross-section of ion and neutral atom elastic collision, σ
3Be the collision cross-section of electronics and neutral atom exciting collision, σ
4Be the collision cross-section of the ionizing collision of electronics and neutral atom, σ
5Be the collision cross-section of ion and the collision of neutral atom charge exchange, σ
6Collision cross-section for the compound collision of electronics and positive ion;
(1.4) for random number R
2, R
2∈ (0,1),
If R
2∈ (0, σ
1/ σ
T), what then take place is collision of the first kind, and elastic collision between electronics and the neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ (σ
1/ σ
T, (σ
1+ σ
2)/σ
T), what then take place is collision of the second kind, and ion and neutral atom elastic collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2)/σ
T, (σ
1+ σ
2+ σ
3)/σ
T), what then take place is the third collision, and electronics and neutral atom exciting collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4)/σ
T), what then take place is the 4th kind of collision, and the ionizing collision of electronics and neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T), what then take place is the 5th kind of collision, and the collision of ion and neutral atom charge exchange promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T, 1), what then take place is the 6th kind of collision, and the compound collision of electronics and positive ion promptly takes place, and gets into step (1.5) afterwards;
(1.5) be collision of the first kind as if what take place, then pass through formula
φ=2 π R
3,
Confirm initiating electron and intended particle collision scattering angle χ afterwards, the movement velocity v ' of i initiating electron of meridian ellipse angle φ and collision back successively, wherein, R
3Be the uniform random number between (0,1), ε
iBe the zero energy of i initiating electron, v is the initial velocity of preceding i the initiating electron of collision, and m is the quality of i initiating electron, and M is the quality of intended particle;
If what take place is collision of the second kind, then pass through formula
φ=2 π R
4, | v
i' |=| v|cos χ confirms the scattering angle χ after the collision of initial ion and intended particle, the movement velocity v of i initial ion of meridian ellipse angle φ and collision back successively
i', wherein, R
4Be random number, R
4∈ (0,1);
As if what take place is the third collision, it is resolved into excite the back elastic collision to handle earlier.Excite the kinetic energy ε of i the initiating electron in back
i'=ε
i-ε
e, ε
eBe the excitation energy of neutral atom, velocity variations does
With this initial velocity, ask for speed and position after the exciting collision according to the method for elastic collision as elastic collision;
If what take place is the 4th kind of collision; Elastic collision was handled after it was resolved into pre-ionization; Can produce a new electronics and a new ion after the ionization, the initial position of the new electronics that produces is identical with i initiating electron after the ionization, and the initial kinetic energy that obtains after the ionization is ε
s=10tan [arctan ((ε
iR
5)/20)], random number R
5∈ (0,1), rapid change does
As the initial velocity of elastic collision, wherein m
eFor the quality of the new electronics that produces, identical with the quality m of i initiating electron, after the collision, the speed of the new electronics that produces and position are confirmed by the principle of elastic collision; Kinetic energy after i initiating electron ionization is ε '=ε
i-ε
0-ε
s, ε
0Be the ionization energy of neutral atom, its velocity variations does
With its initial velocity, ask for i speed and the position after the initiating electron collision according to the principle of elastic collision again as elastic collision; Distribute according to Maxwell for the speed of the ion of new generation and direction and to obtain at random, and be set and be new initial ion, its initial position is identical with i initiating electron position;
If what take place is the 5th kind of collision; After the collision of initial ion and intended particle charge-exchange promptly takes place; The speed of initial ion has become the speed of original intended particle, and this speed obtains based on Maxwell's regularity of distribution at random, the invariant position of collision back initial ion;
If what take place is the 6th kind of collision, the compound collision of initiating electron and intended particle promptly takes place after, form a neutral particle, its position is identical with the position of intended particle, speed obtains according to Maxwell's regularity of distribution at random;
(2) according to preset space lattice subdivision step-length low pressure discharge numerical model in the Space Microwave parts of setting up in the step (1) is decomposed the space lattice unit, confirms total number of electrons, carry out through following steps:
(2.1) use the Maxwell equation group to obtain the electric field and the magnetic field at each place, space lattice unit according to preset original state parameter, obtain the suffered Lorentz force of each particle of Space Microwave part interior again by the Lorentz force formula;
(2.2) Lorentz force that receives according to particle in the space lattice unit obtains the initial velocity and the initial position of particle, and then obtains the initial kinetic energy of particle;
(2.3) execution in step (1.1) writes down the total number of electrons that generates after the collision in all space lattice unit of Space Microwave parts in each time step Δ t to step (1.5); And long Δ t advances by time step, and total number of electrons in each Δ t time period is exported in repeating step (2.1)～(2.3) till reaching preset computing time, obtain number of electrons total in Space Microwave parts rule over time;
(3) power input of change Space Microwave parts; Execution in step (2), under the record different input power, total number of electrons is over time in all space lattice unit in preset computing time; If total number of electrons is all keeping balance above in 100 rf periods; Power input that then will this moment is defined as the low pressure discharge threshold value of Space Microwave parts, when power input during greater than this threshold value, and Space Microwave parts generation low pressure discharge effect then.
The present invention's beneficial effect compared with prior art is:
(1) the present invention is based on the calculating particles method; Set up low pressure discharge numerical model in the Space Microwave parts; The motion process of charged particle in the low pressure discharge and total number of electrons are carried out numerical simulation calculation, obtained the low pressure discharge threshold value of Space Microwave parts.Adopt Space Microwave parts low pressure discharge method for numerical simulation of the present invention, can avoid obtaining the low pressure discharge threshold value of Space Microwave parts, shorten the design cycle, reduce development cost through experiment repeatedly.
(2) the Space Microwave parts method for numerical simulation of the present invention's proposition; Not only considered the collision that takes place in the microwave component gas space; Also considered the multipactor of electronics and microwave component inner metal surfaces; The discharge process of overlaping stages between the gas breakdown that micro discharge effect that takes place under can the numerical simulation vacuum environment and hyperbaric environment take place down, the accuracy of the low pressure discharge threshold value that has guaranteed to be calculated.
(3) in the Space Microwave parts that the present invention set up in the low pressure discharge numerical model; Prevailing all crash types in the microwave component gas space have been considered; It is the elastic collision of elastic collision, ion and the neutral particle of electronics and neutral particle; The accuracy of low pressure discharge method for numerical simulation in the Space Microwave parts has been guaranteed in charge exchange collision between the exciting collision of electronics and neutral particle and ionizing collision, ion and the neutral atom and the compound collision between electronics and the positive ion.
Description of drawings
Fig. 1 is that the velocity reversal before and after the elastic collision changes synoptic diagram
Fig. 2 is the structural drawing of S-band impedance transformer
Fig. 3 is the low pressure discharge threshold curve of S-band impedance transformer
Fig. 4 is a process flow diagram of the present invention
Embodiment
The present invention proposes a kind of Space Microwave parts low pressure discharge method for numerical simulation; It comprises has set up Space Microwave parts low pressure discharge numerical model; Carry out accurate numerical analysis to the motion process of charged particle in the low pressure discharge and total number of electrons, obtained the low pressure discharge threshold value of Space Microwave parts.The present invention has considered the multipactor of Space Microwave parts metal surfaces, can analyze under the vacuum environment discharge discharge down with hyperbaric environment between discharge threshold under the hypobaric of overlaping stages.Consider prevailing all crash types in the microwave component gas space simultaneously, guaranteed the accuracy of low pressure discharge method for numerical simulation in the Space Microwave parts.When model is carried out numerical evaluation, microwave component is carried out mesh generation in addition, in the space lattice unit, calculate the motion of electromagnetic field and particle, can analyze the microwave component structure of relative complex.The present invention can avoid obtaining through experiment repeatedly the low pressure discharge threshold value of Space Microwave parts, shortens the design cycle, reduces development cost, is highly suitable for the numerical analysis of low pressure discharge in the Space Microwave parts.
As shown in Figure 4; The invention provides a kind of Space Microwave parts low pressure discharge method for numerical simulation; The particle of said Space Microwave part interior comprises primary and intended particle, and intended particle generally is bigger neutral gas atom or the molecule of proportion in the gas componant of microwave component inner space, and movement velocity is relatively slow; Distribute by Maxwell's regularity of distribution, evenly distribute on the space.And primary generally is a movement velocity particle faster, as accounts for the less charged particle that but low pressure discharge is played an important role of gas componant proportion.Primary is divided into initiating electron and initial ion by its charging property, and step is following:
(1) set up low pressure discharge numerical model in the Space Microwave parts based on the method for particle simulation, specifically pass through following steps:
(1.1) according to i primary in preset time step Δ t; Judge from the displacement that an initial position moves to another position whether this primary bumps with Space Microwave parts inside surface metal boundary; If the primary displacement of in Δ t, moving more than or equal to its initial position to the distance of metal boundary; Then bump, get into step (1.2); If the primary displacement of in Δ t, moving, does not then bump to the distance of metal boundary less than its initial position, get into step (1.3); Here, the displacement during n+1 time step is calculated by formula (1) and obtains.
Displacement when wherein
representes n time step; Kinetic energy during n+1/2 time step of
expression; M representes x; Y, the component on three directions of z.
(1.2) judge whether to take place the secondary electron multiplication according to the initial kinetic energy of i primary and the secondary electron emission characteristic of microwave component inside surface metal material.If produce k secondary electron after the primary collision metallic walls, and δ
MaxAs new primary is then regarded the secondary electron of launching in>=k>=1, and the original state with their kinetic energy and displacement is made as next time step gets into step (2) afterwards, wherein, and δ
MaxBe the maximum secondary electron emission coefficiency, by preset Space Microwave parts surface metal material characteristic decision; If multipactor does not then take place in k≤1, think that i primary absorbed by metal material.
(1.3) judge whether primary bumps with intended particle among the Space Microwave part interior gas space, if R is arranged
1＜P
iSet up, think that then primary collision has taken place for i primary and intended particle, get into step (1.4) afterwards, otherwise think and do not bump, i primary continuation moved, and gets back to step (1.1); Wherein, R
1Be a random number and R
1∈ (0,1), P
iFor total collision probability and P is arranged
i=1-exp (σ
T(ε
i) n
t(x
i) v
iΔ t), n
t(x
i) be the intended particle density of i primary position, v
iBe the initial velocity of i primary, σ
T(ε
i) be total collision cross-section and σ
T(ε
i)=σ
1(ε
i)+σ
2(ε
i)+... + σ
6(ε
i), σ
1(ε
i), σ
2(ε
i) ... σ
6(ε
i) be the collision cross-section of contingent 6 kinds of collisions between i primary and the intended particle, the acquisition of can tabling look-up.For each gas, the crash type of being considered is also not exclusively the same, as shown in table 1.
Wherein, σ
1Be the collision cross-section of elastic collision between electronics and the neutral atom, σ
2Be the collision cross-section of ion and neutral atom elastic collision, σ
3Be the collision cross-section of electronics and neutral atom exciting collision, σ
4Be the collision cross-section of the ionizing collision of electronics and neutral atom, σ
5Be the collision cross-section of ion and the collision of neutral atom charge exchange, σ
6Collision cross-section for the compound collision between electronics and the positive ion.
The crash type that table 1 gas with various is corresponding
| Gas type | The electron collision type of considering | The ion collision type of considering |
| Ar | Elastic collision, excite, ionization | Elastic collision, charge exchange |
| N | Elastic collision, ionization | Do not have |
| O | Elastic collision, ionization | Do not have |
| Ne | Elastic collision, excite, ionization, compound | Charge exchange |
| Xe | Elastic collision, excite, ionization | Charge exchange |
| H | Ionization | Do not have |
| Li | Elastic collision, ionization | Do not have |
(1.4) for random number R
2, R
2∈ (0,1),
If R
2∈ (0, σ
1/ σ
T), what then take place is collision of the first kind, and elastic collision between electronics and the neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ (σ
1/ σ
T, (σ
1+ σ
2)/σ
T), what then take place is collision of the second kind, and ion and neutral atom elastic collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2)/σ
T, (σ
1+ σ
2+ σ
3)/σ
T), what then take place is the third collision, and electronics and neutral atom exciting collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4)/σ
T), what then take place is the 4th kind of collision, and the ionizing collision of electronics and neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T), what then take place is the 5th kind of collision, and the collision of ion and neutral atom charge exchange promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T, 1), what then take place is the 6th kind of collision, and the compound collision between electronics and the positive ion promptly takes place, and gets into step (1.5) afterwards.
(1.5) be collision of the first kind as if what take place, the change of collision back direction of motion is at random, confirms direction of motion by scattering angle χ and meridian ellipse angle φ, and is as shown in Figure 1, through formula
φ=2 π R
3,
Confirm initiating electron and intended particle collision scattering angle χ afterwards, the movement velocity v ' of i initiating electron of meridian ellipse angle φ and collision back successively, wherein, R
3Be the uniform random number between (0,1), ε
iBe the zero energy of i initiating electron, v is the initial velocity of preceding i the initiating electron of collision, and m is the quality of i initiating electron, and M is the quality of intended particle;
If what take place is collision of the second kind, then pass through formula
φ=2 π R
4, | v
i' |=| v|cos χ confirms the scattering angle χ after the collision of initial ion and intended particle, the movement velocity v of i initial ion of meridian ellipse angle φ and collision back successively
i', wherein, R
4Be random number, R
4∈ (0,1);
As if what take place is the third collision, it is resolved into excite the back elastic collision to handle earlier.Excite the kinetic energy ε of i the initiating electron in back
i'=ε
i-ε
e, ε
eBe the excitation energy of neutral atom, velocity variations does
With this initial velocity, ask for speed and position after the exciting collision according to the method for elastic collision as elastic collision;
If what take place is the 4th kind of collision; Elastic collision was handled after it was resolved into pre-ionization; Can produce a new electronics and a new ion after the ionization, the initial position of the new electronics that produces is identical with i initiating electron after the ionization, and the initial kinetic energy that obtains after the ionization is ε
s=10tan [arctan ((ε
iR
5)/20)], random number R
5∈ (0,1), rapid change does
As the initial velocity of elastic collision, wherein m
eFor the quality of the new electronics that produces, identical with the quality m of i initiating electron, after the collision, the speed of the new electronics that produces and position are confirmed by the principle in the elastic collision; Kinetic energy after i initiating electron ionization is ε '=ε
i-ε
0-ε
s, ε
0Be the ionization energy of neutral atom, its velocity variations does
With its initial velocity, ask for i speed and the position after the initiating electron collision according to the principle of elastic collision again as elastic collision; Distribute according to Maxwell for the speed of the ion of new generation and direction and to obtain at random, and be set and be new initial ion, its initial position is identical with i initiating electron position;
If what take place is the 5th kind of collision; After the collision of initial ion and intended particle charge-exchange promptly takes place; The speed of initial ion has become the speed of original intended particle, and this speed obtains based on Maxwell's regularity of distribution at random, the invariant position of collision back initial ion;
If what take place is the 6th kind of collision, the compound collision of initiating electron and intended particle promptly takes place after, form a neutral particle, its position is identical with the position of intended particle, speed obtains according to Maxwell's regularity of distribution at random;
(2) according to the work centre frequency and the minimum dimension structure of Space Microwave parts; Microwave component is split into a plurality of rectangular build space lattices; And obtain the material parameter and the secondary electron emission characteristic parameter of metal section and part space lattice unit in the microwave component by preset metal material, obtain the characterisitic parameter of the space lattice unit of microwave component gas space according to the characteristic of the gas space.According to preset space lattice subdivision step-length low pressure discharge numerical model in the Space Microwave parts of setting up in the step (1) is decomposed the space lattice unit, confirms total number of electrons, carry out through following steps:
(2.1) use the Maxwell equation group to obtain the electric field and the magnetic field at each place, space lattice unit according to preset original state parameter, obtain the suffered Lorentz force of each space particle by the Lorentz force formula again.
(2.2) Lorentz force that receives according to particle in the space lattice unit obtains the initial velocity distribution initial position of particle, and then obtains the initial kinetic energy of particle.
(2.3) execution in step (1.1) is to step (1.5); Write down the total number of particles that generates after the collision in all space lattice unit of Space Microwave parts in each time step Δ t; In the process that obtains total number of electrons, in each Δ t, upgrade the electromagnetic field value on the space lattice cell node.
Long Δ t advances by time step, and total number of electrons in each Δ t time period is exported in repeating step (2.1)～(2.3) till reaching preset computing time, obtain number of electrons total in Space Microwave parts rule over time.
(3) power input of change Space Microwave parts; Execution in step (2); Under the record different input power; Number of particles if total number of electrons all can keep balance above in 100 rf periods, then is defined as the power input of this moment the threshold value of Space Microwave parts low pressure discharge over time in all space lattice unit in preset computing time.When power input during greater than this threshold value, Space Microwave parts generation low pressure discharge effect then.
Below just in the low pressure discharge numerical simulation process of S-band impedance transformer summary embodiment:
1, the air pressure in setting space microwave component space of living in is that 1mBar, gas type are nitrogen; Parts inside surface metal material is a silver, and S-band impedance transformer structural drawing is as shown in Figure 2, and working band is 3.1-3.4GHz; Insertion Loss is＜0.4dB that the power input of impedance transformer is P in the band.According to microwave component structure setting space mesh generation step-length, computing time be 100ns, it is 0.5ns that particle advances time step.
2, calculate electric field and the magnetic field that particle receives according to the original state that is provided with in the step 1 in each space lattice unit, obtain the suffered Lorentz force of each space particle by the Lorentz force formula again;
3, the Lorentz force that receives according to particle in the space lattice unit obtains initial velocity, initial position and the initial kinetic energy of particle;
4,, write down the total number of electrons that generates after the collision in all space lattice unit of S-band impedance transformer in each time step Δ t according to Space Microwave parts low pressure discharge numerical model.And long Δ t carries out the loop iteration numerical simulation by time step, till reaching preset computing time, exports in each Δ t time period total number of electrons in all space lattice unit of S-band impedance transformer.
5, change different input power P, obtain corresponding total number of electrons over time.When power input is 680.02W; Total number of electrons still keeps balance when surpassing 31.25ns; Then think under present circumstances; The low pressure discharge threshold value of S-band impedance transformer is 680.02W, when power input during greater than this threshold value, and this S-band impedance transformer generation low pressure discharge effect.
6, change the interior atmospheric pressure value of impedance transformer, air pressure range is 1-12mBar, and step-length is 1.Note the corresponding low pressure discharge threshold value of different air pressure, draw the low pressure discharge threshold curve that obtains this S-band impedance transformer, as shown in Figure 3.
The content of not doing to describe in detail in the instructions of the present invention belongs to this area professional and technical personnel's known technology.
Claims (1)
1. Space Microwave parts low pressure discharge method for numerical simulation, the particle of said Space Microwave part interior comprises primary and intended particle, primary is divided into initiating electron and initial ion by its charging property, it is characterized in that step is following:
(1) set up low pressure discharge numerical model in the Space Microwave parts based on the method for particle simulation, specifically pass through following steps:
(1.1) according to i primary in preset time step Δ t; Judge from the displacement that an initial position moves to another position whether this primary bumps with Space Microwave parts inside surface metal boundary; If the primary displacement of in Δ t, moving more than or equal to its initial position to the distance of metal boundary; Then bump, get into step (1.2); If the primary displacement of in Δ t, moving, does not then bump to the distance of metal boundary less than its initial position, get into step (1.3);
(1.2) judge whether to take place the secondary electron multiplication according to the initial kinetic energy of i primary and the secondary electron emission characteristic of microwave component inside surface metal material; If taking place, the secondary electron multiplication produces secondary electron; Then regard the secondary electron of launching as new particle; Original state with their kinetic energy and displacement is made as next time step gets into step (2) afterwards; If the secondary electron multiplication does not take place, thinks that then i primary absorbed by metal material;
(1.3) judge whether primary bumps with intended particle in the Space Microwave part interior gas space, if R is arranged
1＜P
iSet up, think that then primary collision has taken place for i primary and intended particle, get into step (1.4) afterwards, otherwise think and do not bump, i primary continuation moved, and gets back to step (1.1); Wherein, R
1Be a random number and R
1∈ (0,1), P
iFor total collision probability and P is arranged
i=1-exp (σ
T(ε
i) n
t(x
i) v
iΔ t), v
iBe the initial velocity of i primary, n
t(x
i) be the density of i primary position intended particle, σ
T(ε
i) be total collision cross-section and σ is arranged
T(ε
i)=σ
1(ε
i)+σ
2(ε
i)+σ
3(ε
i)+σ
4(ε
i)+σ
5(ε
i)+σ
6(ε
i), σ
1(ε
i), σ
2(ε
i) ... σ
6(ε
i) be the collision cross-section of contingent 6 kinds of collisions between i primary and the intended particle, the acquisition of can tabling look-up;
Wherein, σ
1Be the collision cross-section of elastic collision between electronics and the neutral atom, σ
2Be the collision cross-section of ion and neutral atom elastic collision, σ
3Be the collision cross-section of electronics and neutral atom exciting collision, σ
4Be the collision cross-section of the ionizing collision of electronics and neutral atom, σ
5Be the collision cross-section of ion and the collision of neutral atom charge exchange, σ
6Collision cross-section for the compound collision of electronics and positive ion;
(1.4) for random number R
2, R
2∈ (0,1),
If R
2∈ (0, σ
1/ σ
T), what then take place is collision of the first kind, and elastic collision between electronics and the neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ (σ
1/ σ
T, (σ
1+ σ
2)/σ
T), what then take place is collision of the second kind, and ion and neutral atom elastic collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2)/σ
T, (σ
1+ σ
2+ σ
3)/σ
T), what then take place is the third collision, and electronics and neutral atom exciting collision promptly take place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4)/σ
T), what then take place is the 4th kind of collision, and the ionizing collision of electronics and neutral atom promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4)/σ
T, (σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T), what then take place is the 5th kind of collision, and the collision of ion and neutral atom charge exchange promptly takes place, and gets into step (1.5) afterwards;
If R
2∈ ((σ
1+ σ
2+ σ
3+ σ
4+ σ
5)/σ
T, 1), what then take place is the 6th kind of collision, and the compound collision of electronics and positive ion promptly takes place, and gets into step (1.5) afterwards;
(1.5) be collision of the first kind as if what take place, then pass through formula
φ=2 π R
3,
Confirm initiating electron and intended particle collision scattering angle χ afterwards, the movement velocity v ' of i initiating electron of meridian ellipse angle φ and collision back successively, wherein, R
3Be the uniform random number between (0,1), ε
iBe the zero energy of i initiating electron, v is the initial velocity of preceding i the initiating electron of collision, and m is the quality of i initiating electron, and M is the quality of intended particle;
If what take place is collision of the second kind, then pass through formula
φ=2 π R
4, | v
i' |=| v|cos χ confirms the scattering angle χ after the collision of initial ion and intended particle, the movement velocity v of i initial ion of meridian ellipse angle φ and collision back successively
i', wherein, R
4Be random number, R
4∈ (0,1);
As if what take place is the third collision, it is resolved into excite the back elastic collision to handle earlier.Excite the kinetic energy ε of i the initiating electron in back
i'=ε
i-ε
e, ε
eBe the excitation energy of neutral atom, velocity variations does
With this initial velocity, ask for speed and position after the exciting collision according to the method for elastic collision as elastic collision;
If what take place is the 4th kind of collision; Elastic collision was handled after it was resolved into pre-ionization; Can produce a new electronics and a new ion after the ionization, the initial position of the new electronics that produces is identical with i initiating electron after the ionization, and the initial kinetic energy that obtains after the ionization is ε
s=10tan [arctan ((ε
iR
5)/20)], random number R
5∈ (0,1), rapid change does
As the initial velocity of elastic collision, wherein m
eFor the quality of the new electronics that produces, identical with the quality m of i initiating electron, after the collision, the speed of the new electronics that produces and position are confirmed by the principle of elastic collision; Kinetic energy after i initiating electron ionization is ε '=ε
i-ε
0-ε
s, ε
0Be the ionization energy of neutral atom, its velocity variations does
With its initial velocity, ask for i speed and the position after the initiating electron collision according to the principle of elastic collision again as elastic collision; Distribute according to Maxwell for the speed of the ion of new generation and direction and to obtain at random, and be set and be new initial ion, its initial position is identical with i initiating electron position;
If what take place is the 5th kind of collision; After the collision of initial ion and intended particle charge-exchange promptly takes place; The speed of initial ion has become the speed of original intended particle, and this speed obtains based on Maxwell's regularity of distribution at random, the invariant position of collision back initial ion;
If what take place is the 6th kind of collision, the compound collision of initiating electron and intended particle promptly takes place after, form a neutral particle, its position is identical with the position of intended particle, speed obtains according to Maxwell's regularity of distribution at random;
(2) according to preset space lattice subdivision step-length low pressure discharge numerical model in the Space Microwave parts of setting up in the step (1) is decomposed the space lattice unit, confirms total number of electrons, carry out through following steps:
(2.1) use the Maxwell equation group to obtain the electric field and the magnetic field at each place, space lattice unit according to preset original state parameter, obtain the suffered Lorentz force of each particle of Space Microwave part interior again by the Lorentz force formula;
(2.2) Lorentz force that receives according to particle in the space lattice unit obtains the initial velocity and the initial position of particle, and then obtains the initial kinetic energy of particle;
(2.3) execution in step (1.1) writes down the total number of electrons that generates after the collision in all space lattice unit of Space Microwave parts in each time step Δ t to step (1.5); And long Δ t advances by time step, and total number of electrons in each Δ t time period is exported in repeating step (2.1)～(2.3) till reaching preset computing time, obtain number of electrons total in Space Microwave parts rule over time;
(3) power input of change Space Microwave parts; Execution in step (2), under the record different input power, total number of electrons is over time in all space lattice unit in preset computing time; If total number of electrons is all keeping balance above in 100 rf periods; Power input that then will this moment is defined as the low pressure discharge threshold value of Space Microwave parts, when power input during greater than this threshold value, and Space Microwave parts generation low pressure discharge effect then.
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