Model and simulation method for emitting microcosmic hot electrons to macroscopic electromagnetic pulses
By coupling PIC simulation with three-dimensional electromagnetic field simulation, the problem of the disconnect between microscopic and macroscopic aspects in existing EMP simulation methods is solved. It realizes the integrated simulation of the entire chain from microscopic hot electrons to macroscopic electromagnetic radiation, improves the prediction accuracy and the reliability of experimental data, and is suitable for electromagnetic pulse management and protection design of high-power laser devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-04-14
AI Technical Summary
Existing EMP simulation methods cannot uniformly describe the entire process from microscopic hot electron emission to macroscopic electromagnetic radiation, resulting in low prediction accuracy. Furthermore, traditional methods ignore the spatial distribution of hot electrons, making it difficult to explain complex radiation environments and understand the coupling mechanism between laser parameters and target material properties.
By employing a coupled PIC simulation and three-dimensional electromagnetic field simulation method, and through particle simulation and electromagnetic field simulation models, we can achieve integrated simulation of the entire chain from microscopic particle dynamics to macroscopic electromagnetic radiation. By combining laser parameters and target characteristics, we can accurately calculate thermionic parameters and simulate the spatiotemporal evolution of electromagnetic pulses.
It enables precise prediction and control of EMP, improves the accuracy of experimental data and the electromagnetic protection design of equipment, provides theoretical support for strong field physics and electromagnetic compatibility testing, and is applicable to electromagnetic pulse management of different laser devices.
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Figure CN121859683A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-power laser physics and electromagnetic pulse simulation technology, and particularly relates to a model and simulation method for microscopic hot electron emission into macroscopic electromagnetic pulses. Background Technology
[0002] With the development of high-power laser technology, electromagnetic pulses (EMPs) generated by the interaction of lasers with solid targets are widely used in strong-field physics, materials science, and electromagnetic compatibility testing due to their high intensity (kV / m to MV / m) and wide spectrum (MHz to GHz). However, existing EMP simulation methods have the following shortcomings: 1. A single model (such as particle simulation or electromagnetic model) cannot uniformly describe the entire process from microscopic hot electron emission to macroscopic electromagnetic radiation, resulting in low prediction accuracy; 2. Traditional methods such as the half-wave dipole antenna model (see document 2) Figure 1 1) Considering only the neutralization current and neglecting the contribution of the spatial distribution of hot electrons to EMP makes it difficult to explain complex radiation environments; 2) The EMP intensity generated by picosecond lasers is higher than that of nanosecond or femtosecond lasers, but existing simulation methods cannot effectively couple laser parameters (such as energy and focal length) with the characteristics of the target material, limiting the understanding of the EMP amplification mechanism. Therefore, there is an urgent need for a coupled simulation method that can integrate microscopic hot electron dynamics and macroscopic electromagnetic field distribution to achieve accurate prediction and control of EMP. Summary of the Invention
[0003] To address the problems of fragmented models and inaccurate predictions in existing technologies, this invention provides a model and simulation method for microscopic hot electron emission into macroscopic electromagnetic pulses. By coupling PIC simulation with three-dimensional electromagnetic field simulation, it achieves integrated simulation of the entire chain from microscopic particle dynamics to macroscopic electromagnetic radiation, which is suitable for predicting and optimizing the characteristics and spatial distribution of electromagnetic pulses generated by the interaction between laser and target.
[0004] A model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse includes the following steps:
[0005] S1: Determine the laser parameters and target parameters based on the laser's performance parameters and the mission type. The laser parameters include energy, pulse width, focusing size, and focal length power density, while the target parameters include material, thickness, and shape.
[0006] S2: Input the laser parameters and target parameters into a pre-built particle simulation model of laser-solid target interaction to simulate the escape electron parameters of the target under laser action. The escape electron parameters include escape electron angular distribution, electron energy spectrum and charge.
[0007] S3: Determine whether the escape electron parameters are correct, and perform error compensation for escape electron parameters whose judgment result is yes;
[0008] S4: Input the escape electron parameters after error compensation into the pre-constructed three-dimensional model of the target chamber, and simulate the three-dimensional electromagnetic pulse radiation field caused by the neutralization current generated by the target under the action of the laser, which flows from the target through the target rod to the ground, and the space charge current generated by the movement of charged particles in space under the action of the laser.
[0009] Furthermore, the method for determining whether the escape electron parameters are correct is as follows:
[0010] Determine whether the propagation mode of the laser in the target violates the principles of physics;
[0011] Determine whether the electron number density in the target before and during laser treatment conforms to actual physical laws;
[0012] Determine whether there is a difference in magnitude between the electron energy spectrum obtained after laser treatment and the electron energy spectrum measured in actual experiments;
[0013] If all the judgment results are negative, then the escape electron parameters are correct.
[0014] Furthermore, error compensation for escape electronic parameters for cases where the judgment result is yes includes:
[0015] Compensation is provided for the total charge error and the average energy error in the electron energy spectrum.
[0016] Furthermore, in step S3, if the structure is determined to be incorrect, the process returns to step S1, and the laser parameters and target parameters are re-determined based on the laser's performance parameters and the task type before proceeding to steps S2-S3.
[0017] Furthermore, the particle simulation model of the laser-solid target interaction is pre-built using EPOCH simulation software.
[0018] Furthermore, the three-dimensional model of the target chamber includes a target, a target rod, and a chamber structure.
[0019] Furthermore, the electromagnetic simulation method in step S4 includes the finite element method or the finite-difference time-domain method.
[0020] Furthermore, a model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse also includes the following steps:
[0021] S5: Based on the three-dimensional radiation field of the electromagnetic pulse, predict the spatiotemporal evolution law and spectral characteristics of the electromagnetic pulse generated by the target under the action of the laser.
[0022] Beneficial effects:
[0023] 1. This invention provides a model and simulation method for the emission of microscopic hot electrons into macroscopic electromagnetic pulses. It innovatively couples particle simulation with three-dimensional electromagnetic field simulation, achieving integrated simulation of the entire chain from microscopic particle dynamics to macroscopic electromagnetic radiation. This effectively solves the technical problem of the disconnect between microscopic mechanisms and macroscopic manifestations in traditional simulation methods. Furthermore, this invention possesses good versatility and adaptability, fully considering the influence of multiple factors such as laser parameters, target material characteristics, and experimental environment. By adjusting simulation parameters, the characteristics of electromagnetic pulses under different experimental conditions can be accurately predicted, providing reliable theoretical guidance for optimizing experimental design schemes. This method is not only applicable to the performance evaluation of existing laser devices but also provides technical support for the electromagnetic pulse management of future higher-power laser devices.
[0024] 2. This invention provides a model and simulation method for the emission of microscopic hot electrons into macroscopic electromagnetic pulses. By establishing a comprehensive simulation framework, it can accurately reproduce the generation, acceleration, and transport processes of hot electrons during the interaction between laser and matter, and accurately predict the spatiotemporal evolution and spectral characteristics of the resulting electromagnetic pulses. Specifically, laser and target parameters can be determined in the pre-experimental preparation stage, and the escape electron information can be obtained through simulation using the modified PIC simulation code in EPOCH. This information is then substituted into a three-dimensional electromagnetic field simulation to realize the intensity and spatial distribution of the electromagnetic pulse under these laser and target parameters. This multi-physics coupled simulation method provides a new perspective and research tool for understanding the generation mechanism of laser-driven electromagnetic pulses.
[0025] 3. This invention provides a model and simulation method for the emission of microscopic hot electrons into macroscopic electromagnetic pulses. In practical applications, this simulation method provides important technical means for the electromagnetic protection design of laser devices, the layout optimization of diagnostic equipment, and the reasonable interpretation of experimental data. By predicting the intensity distribution and propagation characteristics of electromagnetic pulses through pre-simulation, targeted shielding measures can be taken to effectively protect precision diagnostic equipment from electromagnetic interference and ensure the reliability and accuracy of experimental data. Simultaneously, this method can also provide strong theoretical support for the technological development in related fields. Attached Figure Description
[0026] Figure 1 The flowchart shows a model and simulation method for microscopic hot electron emission into a macroscopic electromagnetic pulse provided by this invention.
[0027] Figure 2 A schematic diagram of PIC simulation results based on the SG-II UP laser device in Embodiment 1 of the present invention.
[0028] Figure 3 A schematic diagram of the target chamber model of the SG-II UP laser device in Embodiment 1 provided by the present invention.
[0029] Figure 4 A schematic diagram of the three-dimensional electromagnetic field simulation results based on the SG-II UP laser device in Embodiment 1 of the present invention.
[0030] Figure 5 A schematic diagram of a three-dimensional electromagnetic field pulse based on an SG-II UP laser device in Embodiment 1 of the present invention.
[0031] Figure 6 This is a schematic diagram of the measured electromagnetic pulse intensity results based on the SG-II UP laser device in Embodiment 1 of the present invention.
[0032] Figure 7 This is a schematic diagram of the target chamber model of the XG-III laser device in Embodiment 2 of the present invention.
[0033] Figure 8 A schematic diagram of PIC simulation results based on the XG-III laser device in Embodiment 2 of the present invention.
[0034] Figure 9 A schematic diagram of the three-dimensional electromagnetic field simulation results based on the XG-III laser device in Embodiment 2 of the present invention.
[0035] Figure 10 This is a schematic diagram of the measured electromagnetic pulse intensity results based on the XG-III laser device in Embodiment 2 of the present invention. Detailed Implementation
[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
[0037] like Figure 1 As shown, a model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse includes the following steps:
[0038] S1: Determine the laser parameters and target parameters based on the laser's performance parameters and the mission type. The laser parameters include energy, pulse width, focusing size, and focal length power density, while the target parameters include material, thickness, and shape.
[0039] It should be noted that the laser parameters satisfy the relativistic laser intensity, the target materials include metals such as gold, tantalum, and copper, as well as foam targets, and the target shapes include planar targets and other shapes.
[0040] S2: Input the laser parameters and target parameters into a pre-built particle simulation model of laser-solid target interaction to simulate the escape electron parameters of the target under laser action. The escape electron parameters include escape electron angular distribution, electron energy spectrum and charge.
[0041] It should be noted that this invention constructs a particle simulation model of laser-solid target interaction (PIC) using EPOCH's built-in equations and code structure. This code is based on a self-consistent relativistic electromagnetic particle model. The simulation self-consistently solves Maxwell's equations describing the evolution of the electromagnetic field and the relativistic Lorentz force equation describing the interaction between an ultra-intense laser and charged particles in plasma. This enables the simulation of thermionic emission from the laser-solid target interaction, obtaining information such as the angular distribution, energy spectrum, and charge of laser-driven thermionic emission. The thermionic data includes relativistic electron beams with electron energies of 0.1–50 MeV and charges of 50–500 nC, which are then used as a time-varying charge source in the subsequent three-dimensional target chamber model.
[0042] S3: Determine whether the escape electron parameters are correct, and perform error compensation for escape electron parameters whose judgment result is yes;
[0043] The method for determining whether the escape electron parameters are correct is as follows:
[0044] Determine whether the propagation mode of the laser in the target violates physical principles; determine whether the electron number density in the target before and during laser action conforms to actual physical laws; determine whether there is an order of magnitude difference between the electron energy spectrum obtained after laser action and the electron energy spectrum measured in actual experiments; if the results of all judgments are negative, then the escape electron parameters are correct.
[0045] Therefore, the main criteria for judging the correctness of this invention are: 1. The laser-matter interaction process does not violate physical principles. For example, the propagation mode of the laser in the target is completely different for metal solid targets and low-density foam targets; 2. The electron number density is correct. The electron number density in the target before the laser action and during the electron action should conform to the actual physical laws; 3. There is no difference in magnitude between the electron energy spectrum results in the simulation and the electron energy spectrum measured in the experiment.
[0046] Meanwhile, simulation errors mainly include the total charge and average energy in the electron energy spectrum information. These two variables are needed and have a significant impact on the subsequent three-dimensional electromagnetic field simulation. The main source of error is the limitation of the diagnostic equipment in the experiment, which makes it difficult to collect complete electron information. The input parameters in the subsequent three-dimensional electromagnetic field simulation can be compensated by observing the changes in the electron energy spectrum in the simulation results. If the simulation results violate physical laws, the simulation results are considered incorrect, and it is necessary to return to step S1 to recheck the parameters and re-simulate.
[0047] S4: Input the escape electron parameters after error compensation into the pre-constructed three-dimensional model of the target chamber, and simulate the three-dimensional electromagnetic pulse radiation field caused by the neutralization current flowing from the target through the target rod to the ground and the space charge current generated by the space charge current of the charged particles generated by the target under the laser action through the movement of the laser-induced charged particles in space.
[0048] It should be noted that electromagnetic pulses within the target chamber undergo a series of processes, including reflection and the formation of standing waves. The deposition of charged particles also generates electromagnetic pulses. Therefore, a more realistic layout and results will lead to more accurate propagation and distribution of electromagnetic pulses. Based on this, this invention establishes a three-dimensional model using the actual layout of a high-power laser target chamber (including the target chamber geometry, target rod dimensions and material electromagnetic properties, and interior furnishings). This makes the electromagnetic field distribution within the target chamber in the three-dimensional electromagnetic field simulation results closer to the actual situation, laying the model foundation for subsequent particle source substitution.
[0049] Specifically, this invention can be implemented using CST Studio Suite simulation, and the model includes the target chamber reflection effect.
[0050] S5: Based on the three-dimensional radiation field of the electromagnetic pulse, predict the spatiotemporal evolution law and spectral characteristics of the electromagnetic pulse generated by the target under the action of the laser.
[0051] Furthermore, the present invention can also verify the simulation results through experimental data (such as B-dot antenna measurement, charged particle spectrometer measurement, etc.), and further optimize the model parameters of the particle simulation model in step S2 and the target chamber three-dimensional model in step S4, which is applicable to picosecond and femtosecond laser configurations.
[0052] The following section further explains the model and simulation method for laser-driven microscopic hot electron emission into macroscopic electromagnetic pulses provided by this invention, taking into account the specific performance parameters of the laser and the type of task.
[0053] Example 1
[0054] The simulation of a dual picosecond laser-driven EMP based on the SG-II UP laser device is as follows: PIC simulation steps: Input laser parameters: energy 800 J, pulse width 2 ps, focal length power density 2.9 × 10¹ 9 W / cm²; Target parameters: 10 μm thick gold target. Thermionic emission was simulated using PIC code to obtain the electron energy spectrum, and the number density distribution is as follows: Figure 2 As shown. The steps of the 3D electromagnetic field simulation are: Construct a target chamber model, including a spherical cavity (radius 1250 mm) and a cylindrical target rod, etc. (e.g., Figure 3(As shown). The hot electron data output by the PIC was imported into the electromagnetic model as the particle source, set to emit from the target surface, and the spatiotemporal evolution of the electromagnetic pulse was solved to further analyze the characteristics of the laser electromagnetic pulse. The simulation results are as follows. Figure 4 and Figure 5 As shown, the EMP intensity under the coupled source can reach a maximum of 2.5 MV / m. In subsequent experiments, the electromagnetic pulse test results under these laser and target parameters are as follows... Figure 6 As shown, the highest strength can reach 3MV / m, which is close to the strength of 2.5MV / m. The above model and simulation method are well coupled with the actual results and the error is small.
[0055] Example 2
[0056] To further confirm whether the above model and simulation method are consistent with the experimental results, this invention establishes a target chamber model based on XG-III, as shown in the figure. Figure 7 As shown. Based on the laser parameters and target parameters of the XG-III laser device, PIC simulation and three-dimensional electromagnetic field simulation were conducted. The PIC simulation results are shown below. Figure 8 As shown, the electromagnetic simulation results based on the XG-III laser device are as follows: Figure 9 As shown in the figure. The results show that the laser focusing power density of the XG-III laser device is lower than that of the laser focusing power density in Example 1. Therefore, the generated thermionic cutoff energy and charge are lower, and due to the fewer escape electrons, the generated electromagnetic pulse intensity is also weaker, only on the order of hundreds of kV / m. The measured electromagnetic pulse results based on the XG-III laser device are as follows. Figure 10 As shown in the figure. In summary, the simulation results of the above model are consistent with the results of the previous experiments.
[0057] In summary, this invention relates to a model and simulation method for laser-driven microscopic hot electron emission into macroscopic electromagnetic pulses, belonging to the field of high-power laser physics and electromagnetic pulse simulation technology. Addressing the challenge of existing technologies failing to uniformly describe the entire process from microscopic hot electron dynamics to macroscopic electromagnetic radiation, this invention innovatively couples particle simulation (PIC) with three-dimensional electromagnetic field simulation to construct a complete simulation framework. This method first uses PIC to simulate the laser-target interaction process, accurately calculating key parameters such as the energy distribution, angular distribution, and charge of the hot electrons. Then, based on the output data, a three-dimensional electromagnetic field model is established, comprehensively considering the target chamber geometry, material properties, and environmental factors to further solve the spatial evolution process of the electromagnetic pulse. Finally, through a coupling mechanism, the connection from the particle scale to the field scale is achieved, accurately predicting the spatiotemporal evolution, spectral characteristics, and intensity distribution of the electromagnetic pulse. This invention can effectively simulate the complex electromagnetic environment generated in picosecond laser devices (such as kilojoule-level laser systems), providing a new perspective for understanding the physical mechanism of laser-driven electromagnetic pulses. It also possesses high adaptability, allowing for optimization of prediction results by adjusting laser parameters (such as energy, pulse width, and focal length power density) and target materials. This method is not only applicable to strong field physics experiments and electromagnetic compatibility testing, but also provides reliable theoretical support for the electromagnetic protection design of laser devices and the optimization of diagnostic equipment layout. It significantly improves the accuracy of experimental data and the reliability of equipment, and has broad application prospects and technical value.
[0058] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.
Claims
1. A model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse, characterized in that, Includes the following steps: S1: Determine the laser parameters and target parameters based on the laser's performance parameters and the mission type. The laser parameters include energy, pulse width, focusing size, and focal length power density, while the target parameters include material, thickness, and shape. S2: Input the laser parameters and target parameters into a pre-built particle simulation model of laser-solid target interaction to simulate the escape electron parameters of the target under laser action. The escape electron parameters include escape electron angular distribution, electron energy spectrum and charge. S3: Determine whether the escape electron parameters are correct, and perform error compensation for escape electron parameters whose judgment result is yes; S4: Input the escape electron parameters after error compensation into the pre-constructed three-dimensional model of the target chamber, and simulate the three-dimensional electromagnetic pulse radiation field caused by the neutralization current generated by the target under the action of the laser, which flows from the target through the target rod to the ground, and the space charge current generated by the movement of charged particles in space under the action of the laser.
2. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, The method for determining whether the escape electron parameters are correct is as follows: Determine whether the propagation mode of the laser in the target violates the principles of physics; Determine whether the electron number density in the target before and during laser treatment conforms to actual physical laws; Determine whether there is a difference in magnitude between the electron energy spectrum obtained after laser treatment and the electron energy spectrum measured in actual experiments; If all the judgment results are negative, then the escape electron parameters are correct.
3. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, Error compensation for escape electron parameters with a judgment result of "yes" includes: Compensation is provided for the total charge error and the average energy error in the electron energy spectrum.
4. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, In step S3, if the structure is determined to be incorrect, return to step S1, re-determine the laser parameters and target parameters based on the laser's performance parameters and the task type, and then execute steps S2 to S3.
5. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, The particle simulation model of the laser-solid target interaction was pre-built using EPOCH simulation software.
6. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, The three-dimensional model of the target chamber includes the target, the target rod, and the chamber structure.
7. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, characterized in that, The electromagnetic simulation methods in step S4 include the finite element method or the finite-difference time-domain method.
8. The model and simulation method for laser-driven microscopic hot electron emission into a macroscopic electromagnetic pulse as described in claim 1, further comprising the following steps: S5: Based on the three-dimensional radiation field of the electromagnetic pulse, predict the spatiotemporal evolution law and spectral characteristics of the electromagnetic pulse generated by the target under the action of the laser.