Simulation Study Of Electromagnetic Pulses Driven By Ultra-short And Ultra-strong Lasers

The interaction between ultra-short intense laser and material can produce abundant electromagnetic radiation,which covers a wide range of electromagnetic spectrum,covering the wide spectrum of radiofrequency radiation to the gamma ray.However,much of the current research is focused on high frequency radiation,such as ultra-violet light,x-rays and gamma rays,or low-frequency radiation in terahertz.The study of microwave and radio frequency electromagnetic radiation with lower frequency is not deep enough,and the physical experimental evidence is also lacking.It is difficult to obtain a clear understanding of the physical process of generating electromagnetic pulse.Although many researchers have invested in this research field in recent years,the research progress is still in a blank space.With the development of technology,the pulse width and energy of the laser are increased,and its peak power is further improved,even reaching the PW level.And the increase of the laser peak power make the experiments of low-frequency electromagnetic pulse becomes more intense,the special effect of electromagnetic pulse on electronic devices are more significantly.It also requires us to further understanding the physical mechanism of electromagnetic pulse and grasp the pulse characteristics.For this reason,we have carried out the simulation research of ultra-short super laser driven electromagnetic pulse.The physical mechanism,the spectrum characteristic of electromagnetic pulse,the intensity distribution and propagation law and so on several aspects of research are studied.It is hope that simulation study can further understand the physical process,and play a positive role in reference to related experimental work.Specific research work is as follows:1.Using particle simulation method to calculate the interaction of ultra-short intense laser with plasma,produced by high energy electron emergent direction more concentrated,the electron bombardment target chamber can make the target chamber wall in a short period of time after the uneven charge.The physical process of the internal electromagnetic field resonance is simulated with the finite element simulation software,and the cavities wall of 5PW and 45TW are not uniformly charged.The magnetic field generated by the spherical target chamber is obviously stronger in the vicinity of the target chamber wall and above the metal platform,and the characteristic frequency is 288.3MHz.Columnar target chamber of the magnetic field strength in the center of the target chamber and dihedral Angle area is weak;close to the target chamber wall in central region is stronger;the upper metal platform area of the magnetic field is strongest,and the electromagnetic characteristic frequency of 194.8MHz.The complex structural components of the target can change the spatial distribution of the internal magnetic field,and also change the resonance frequency.The simulation can help us to understand the physical process of the electromagnetic pulse generated by the laser driven plasma,and also provide the train of thought for the effective anti-electromagnetic interference design of various diagnostic equipment in the target chamber.2.The electromagnetic pulse generated in the target chamber is simulated through the window to the external propagation process.The peak intensity of the electromagnetic pulse is indicated by the peak electric field intensity,and the peak intensity of the electromagnetic field on the outside of the window is obviously greater than the inside of the window.The wave-front of the electromagnetic pulse is parallel to the metal wall at the initial moment,and then becomes similar to the shape of spherical wave after passing through the window,and the intensity decreases rapidly with the increase of diffusion distance.If the peak electric field intensity of the outside part of the window's axis is changed to represent the weaken of the intensity of the electromagnetic pulse outside the target,the intensity of the peak electric field near the window area is in inverse proportion to the distance,and its value decreases rapidly with the increase of the distance,but in a relatively distant region,The peak electric field intensity decreases linearly with the increase of diffusion distance.The simulation obtained the characteristics of the electromagnetic pulse intensity distribution in each area of the window and explored the attenuation law of the electromagnetic pulse outside the target.It is helpful to understand the propagation of electromagnetic pulse in the target chamber and provide a theoretical basis for the resistance to electromagnetic interference of the equipment.