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CN-122021416-A - Method for determining self-channel propagation of gas discharge plasma of Gaussian beam

CN122021416ACN 122021416 ACN122021416 ACN 122021416ACN-122021416-A

Abstract

The invention belongs to the technical field of plasma discharge, and particularly discloses a method for determining self-channel propagation of gas discharge plasma of a Gaussian beam. The method comprises the steps of acquiring gas collision section data, calculating transport coefficients, constructing an effective diffusion fluid dynamic model, solving the effective diffusion fluid dynamic model by using a rotator time domain finite difference method and the like. According to the invention, through calculating the effective diffusion fluid dynamic model of the interaction of the Gaussian beam and the gas, not only can the electron density evolution of the plasma and the electric field strength evolution of the Gaussian beam be obtained in the gas discharge process, but also the formation and propagation rule of the self-channel can be determined. The method for determining the self-channel propagation of the Gaussian beam gas discharge plasma has the advantages of easy understanding and operation and high calculation efficiency for different gases and Gaussian beams, and has great theoretical and application values.

Inventors

  • BO YONG
  • ZHU ZHIQI
  • GUO XIANMIN
  • LI DAWEI
  • TAO ZHIXIANG
  • LIU XINGLIANG
  • ZHANG YUJIE
  • ZHU YAN

Assignees

  • 安徽大学

Dates

Publication Date
20260512
Application Date
20260115

Claims (10)

  1. 1. A method for determining the self-channel propagation of a Gaussian beam gas discharge plasma is characterized in that, The method comprises the following steps: Step 1, setting parameters of Gaussian beams and gas, wherein the parameters comprise initial beam waist radius, focusing plane, amplitude, angular frequency, propagation time, propagation area, type, density and pressure of the gas of the Gaussian beams; step 2, acquiring gas collision section data in LXCat collision data sets according to the gas types in the step 1; Step 3, calculating a transport coefficient by using the gas collision section data obtained in the step 2, the amplitude, the angular frequency and the gas density of the Gaussian beam set in the step 1 in bolsig + software; step 4, fitting the transport coefficient into a linear function, and initializing the transport coefficient; Step 5, constructing an effective diffusion fluid dynamics model of the interaction of Gaussian beams and plasmas; step 6, initializing Gaussian beams according to parameters of the Gaussian beams set in the step 1; Step 7, solving an effective diffusion fluid dynamic model by using a rotator time domain finite difference method, and calculating the electric field intensity and the magnetic field intensity of a Gaussian beam at the current moment, and the electron energy, the electron speed and the electron density of plasma; Step 8, judging whether the propagation time is reached; If the propagation time is not reached, updating the transport coefficient according to the electron energy of the plasma calculated in the step 7 and the linear function obtained in the step4, and then repeating the step 7; And 9, analyzing the change patterns of the electric field intensity and the electron density of the Gaussian beam in the propagation region and the propagation time, and calculating the self-channel of the plasma.
  2. 2. The method according to claim 1, wherein in the step 1, the initial beam waist radius, focal plane, amplitude, angular frequency, and propagation time of the gaussian beam are defined as 、 、 、 、 The propagation region is a two-dimensional space, and the lengths of the propagation region in the r direction and the z direction are respectively defined as 、 The gas density is defined as 。
  3. 3. The method for determining gaussian beam gas discharge plasma self-channeling according to claim 1, wherein step 2 is specifically: step 2.1. Entering LXCat a collision dataset main interface; step 2.2, selecting a data type, namely a scattering cross section; step 2.3, selecting a database, namely selecting all; step 2.4, selecting a first species according to the gas type set in the step 1; Step 2.5, selecting data sets, namely selecting all data sets; Step 2.6, selecting a chemical reaction process, namely selecting all; And 2.7, outputting gas collision section data, and storing the gas collision section data into a text form.
  4. 4. The method for determining gaussian beam gas discharge plasma self-channeling according to claim 2, wherein step 3 is specifically: step 3.1, bolsig + software is entered, and the gas collision section data obtained in the step 2 are imported; step 3.2, filling in the intensity of the reduced electric field according to the amplitude of the Gaussian beam and the density of the gas set in the step 1; The expression of the reduced electric field strength is: ; Wherein the method comprises the steps of Is the intensity of the reduced electric field; step 3.3, filling in an angular frequency reduction value according to the angular frequency of the Gaussian beam and the density of the gas set in the step 1; the expression of the angular frequency reduction value is: ; Wherein the method comprises the steps of Is an angular frequency reduction value; Calculating a transport coefficient by using bolsig + software according to the gas collision section data, the reduced electric field intensity and the angular frequency reduced value, wherein the transport coefficient comprises ionization frequency, adhesion rate, collision frequency and energy loss rate; and 3.5. Saving the transport coefficient in text form.
  5. 5. The method for determining gaussian beam gas discharge plasma self-channeling according to claim 1, wherein step 4 is specifically: The ionization frequency, the adhesion rate, the collision frequency and the energy loss rate of the transport coefficient obtained in the step 3 are respectively calculated by 、 、 、 Representing that the linear function of the corresponding fitting of each transport coefficient is 、 、 、 The formula is: ; Wherein the method comprises the steps of The fitting slope of each transport coefficient is respectively calculated, For the fitting intercept corresponding to each transport coefficient, U e is electron energy.
  6. 6. The method of determining gaussian beam gas discharge plasma self-channeling according to claim 5, wherein in step 5, an effective diffusion fluid dynamics model is constructed as shown in formulas (1) to (6): (1) (2) (3) (4) (5) (6) Wherein the method comprises the steps of A sign indicating the rotation calculation is given, Indicating the strength of the electric field, Indicating the magnetic flux density of the magnetic field, The time is represented by the time period of the day, The current density is indicated as such, The magnetic field strength is indicated as such, Indicating the density of the electric flux, Representing the effective diffusion coefficient of electrons; 、 、 、 、 respectively representing the charge, density, mass, velocity and energy of electrons; Effective diffusion coefficient of electron Solving by equation (7): (7) Wherein the method comprises the steps of Is the local maxwell relaxation time, And The free diffusion coefficient and the bipolar diffusion coefficient, respectively; Coefficient of free diffusion Solving by equation (8): (8) Wherein μ e is electron mobility, which is solved by equation (9): (9) Bipolar diffusion coefficient Solving by equation (10): (10) wherein μ i is ion mobility, which is solved by equation (11): (11) local maxwell relaxation time Solving by equation (12): (12) wherein ε 0 is the vacuum dielectric constant.
  7. 7. The method of determining gaussian beam gas discharge plasma self-channeling of claim 6, wherein in step 6, the initializing gaussian beam formula is: (13) Wherein the method comprises the steps of The electric field intensities at r 0 and z 0 of the propagation region spatial coordinates, r 0 and z 0 represent the position coordinates in the r and z directions in the propagation region, respectively, W (z 0 ) represents the beam waist radius of the gaussian beam at the z=z 0 plane, and W (z 0 ) is found by equation (14): (14)。
  8. 8. The method of determining gaussian beam gas discharge plasma self-channeling of claim 7, wherein step 7 is specifically: Step 7.1, after the step 6 is completed, entering a rotating body time domain finite difference method, and setting a calculation grid of the rotating body time domain finite difference method according to the propagation area and the propagation time of the Gaussian beam set in the step 1; Step 7.2, solving the formula (1) by using a rotator time domain finite difference method to obtain the electric field intensity in a Gaussian beam propagation area at the current moment, and absorbing the electric field intensity of the Gaussian beam in the propagation area outside the propagation area by using an absorption boundary; step 7.3, solving formulas (2) and (3) by using a rotator time domain finite difference method according to the electric field intensity obtained in the step 7.2 to obtain the magnetic field intensity in the Gaussian beam propagation area at the current moment, and absorbing the magnetic field intensity of the Gaussian beam in the propagation area outside the propagation area by using an absorption boundary; step 7.4, solving a formula (4) by using a rotator time domain finite difference method to obtain electron density in a Gaussian beam propagation area at the current moment, and processing the electron density on the boundary of the propagation area by using a fluid boundary; step 7.5, solving a formula (5) by using a rotator time domain finite difference method to obtain the electron velocity in a Gaussian beam propagation area at the current moment, and processing the electron velocity on the boundary of the propagation area by using a fluid boundary; Step 7.6, solving a formula (6) by using a rotator time domain finite difference method to obtain electron energy in a Gaussian beam propagation area at the current moment, and processing the electron energy on the boundary of the propagation area by using a fluid boundary; And 7.7, respectively storing the electron density and electric field intensity data of the current time propagation region in files E.xlsx and Ne.xlsx, and then exiting the rotator time domain finite difference method.
  9. 9. The method for determining gaussian beam gas discharge plasma self-channeling according to claim 1, wherein in step 8, the method for updating the transport coefficient is as follows: ; Wherein the method comprises the steps of Representing spatial coordinates The energy of the electrons at the location(s), 、 、 、 Respectively, represent a linear function and, 、 、 、 Respectively, the updated ionization frequency, adhesion rate, collision frequency, and energy loss rate.
  10. 10. The method for determining gaussian beam gas discharge plasma self-channeling according to claim 1, wherein in step 9, the calculation process of the plasma self-channeling is specifically: step 9.1, importing space-time field data, namely importing the data files E.xlsx and Ne.xlsx which are obtained in the step 7 and contain the spatial distribution of electric field intensity and electron density at different moments into Origin analysis software; Step 9.2, drawing a physical quantity space-time evolution graph, namely respectively extracting data at different moments for analyzing propagation dynamics, and drawing a contour line distribution graph of electric field intensity and electron density at corresponding moments in a propagation region by using Origin analysis software; Wherein, the contour line distribution diagram intuitively reveals the evolution process of the electric field and the plasma density along with the propagation time; step 9.3, calculating a plasma self-channel; 9.3.1 calculating the plasma frequency of each space point according to the electron density distribution : ; Wherein the method comprises the steps of Representing representation space coordinates Electron density at; Step 9.3.2, identifying, in the propagation space, a region that satisfies the following condition: ; the judging condition is a physical criterion for forming a plasma self-channel; Wherein the method comprises the steps of And (3) with Respectively refers to the angular frequency and the plasma frequency of the Gaussian beam; And 9.3.3. Marking the region boundary determined by the conditions on the contour line distribution diagram of the propagation region by using Origin analysis software on the contour line distribution diagram of the propagation region by using a clear curve, thereby obtaining the plasma self-channel at different moments.

Description

Method for determining self-channel propagation of gas discharge plasma of Gaussian beam Technical Field The invention belongs to the technical field of plasma discharge, and particularly relates to a method for determining self-channel propagation of gas discharge plasma of Gaussian beams. Background After the gaussian beam reaches a certain power, the ionization cross section of the electron beam center is much smaller than that of the electron beam periphery, and the collision ionization rate of the beam periphery is larger than that of the beam axis, so that the too dense plasma is possibly obtained at the periphery of the beam periphery, and the low density is obtained at the center area of the beam center, and the ionization induced self-channeling effect of the strong microwave beam transmitted in the neutral gas is shown. This physical phenomenon was observed in non-patent document 1 using a sub-nanosecond microwave source experiment, and the PIC-MCC model numerical method of 1D was consistent with the experiment. Experiments and numerical simulations demonstrate that this phenomenon is a self-focusing guide channel formed by the nonlinear interactions of electromagnetic waves and plasma due to gas ionization. The mass dynamics of the intense laser as it is transmitted through the plasma is not critical to such self-channeling. The discovery of this phenomenon is of theoretical instructive significance for the application of gaussian beam communication and laser propagation. The study of microwave gas discharge is mainly a PIC-MCC model and a fluid model, and non-patent document 2 proves that the PIC-MCC model is suitable for gaussian beam gas discharge plasma in 2D, and no study on whether the fluid model is suitable for and lacks a 3D calculation method has been made. Prior art literature Non-patent document 1 literature "G. Shafir et al., Ionization-induced self-channeling of an ultrahigh-power subnanosecond microwave beam in a neutral gas, Phys. Rev. Lett., vol. 120, no. 13, p. 135003, Mar. 2018, doi: 10.1103/PhysRevLett.120.135003." Non-patent literature 2 literature "Y. Cao, J. G. Leopold, Y. P. Bliokh, and Ya. E. Krasik, Self-channeling of a powerful microwave beam in a preliminarily formed plasma, Phys. Plasmas, vol. 25, no. 10, p. 103101, Oct. 2018, doi: 10.1063/1.5051226.". Disclosure of Invention The invention aims to provide a method for determining self-channeling of Gaussian beam gas discharge plasma, which improves a fluid model, constructs an effective diffusion fluid dynamics model to determine the self-channeling phenomenon of Gaussian beam gas discharge plasma, couples LXCat collision data sets and bolsig + software to calculate transport coefficients, solves the transport coefficients by using a rotator time domain finite difference method, and can realize 3D high-efficiency numerical analysis on the self-channeling formation and the spreading rule of Gaussian beam gas discharge plasma. In order to achieve the above purpose, the invention adopts the following technical scheme: a method of determining gaussian beam gas discharge plasma self-channeling comprising the steps of: Step 1, setting parameters of Gaussian beams and gas, wherein the parameters comprise initial beam waist radius, focusing plane, amplitude, angular frequency, propagation time, propagation area, type, density and pressure of the gas of the Gaussian beams; step 2, acquiring gas collision section data in LXCat collision data sets according to the gas types in the step 1; Step 3, calculating a transport coefficient by using the gas collision section data obtained in the step 2, the amplitude, the angular frequency and the gas density of the Gaussian beam set in the step 1 in bolsig + software; step 4, fitting the transport coefficient into a linear function, and initializing the transport coefficient; Step 5, constructing an effective diffusion fluid dynamics model of the interaction of Gaussian beams and plasmas; step 6, initializing Gaussian beams according to parameters of the Gaussian beams set in the step 1; Step 7, solving an effective diffusion fluid dynamic model by using a rotator time domain finite difference method, and calculating the electric field intensity and the magnetic field intensity of a Gaussian beam at the current moment, and the electron energy, the electron speed and the electron density of plasma; Step 8, judging whether the propagation time is reached; If the propagation time is not reached, updating the transport coefficient according to the electron energy of the plasma calculated in the step 7 and the linear function obtained in the step4, and then repeating the step 7; And 9, analyzing the change patterns of the electric field intensity and the electron density of the Gaussian beam in the propagation region and the propagation time, and calculating the self-channel of the plasma. The invention has the following advantages: As described above, the invention relates to a method for d