Research On The QED Effect Of Ultrahigh Intensity Laser-plasma Interaction

The urgent need for energy has promoted the rapid development of new energy--fusion energy.And the inertial confinement fusion of the fusion energy has been payed highly attention due to the advantages such as controllability,non-pollution and low raw material cost(deuterium and Tritium in seawater).With the deepening of research on inertial confinement fusion,the intensity of pulsed lasers is also increasing.Especially a key breakthrough in laser technology-chirped-pulse amplification technology has make the maximum peak power of laser pulses to reach 1022 W/cm2 in recent years.And It reaches probably 1023?1024 W/cm2 or even higher in near future.When the laser intensity reaches the order of 1022?1024W/cm2,the laser field strength can be compared with the Schwinger field.The laser-plasma interaction(LPI)will enter the field of strong field quantum electrodynamics(QED)-plasma.The nonlinear strong field QED effect,especially the generation of Gamma ray and electron and positron pairs,will become more complex and important.The combination of the strong field QED effect and LPI has become an important development direction for the present and future years.The strong field QED effect can be studied by means of theory,experiments and numerical simulations.Due to the limitation of computer performance,the research mainly studied by theory and experiments in the early stage.With the rapid improvement of computer performance,numerical simulation methods have become a hotspot in recent years,but the research is still at a development stage,and there are still many problems which need to be further explored and solved.On the one hand,from the respect of physical process,the former researches usually assume that the solid target is completely ionized and distributed uniformly before the numerical simulations.However,it is coupled together with the strong field QED effect,LPI and ionization process in the true situation.The influence mechanism of plasma distribution and ionization process on the strong field QED effect is still unknown according to the author's knowledge;one the other hand,from the respect of theoretical study of the strong field QED effect,whether the theory and model are correct remains to be explored as it is still in the development stage.In addition,EPOCH program which is Developed by the university of Warwick is the only widely used mainstream program now.It is necessary to develop a numerical simulation programs based on the existing QED effect theories as quickly as we can,so that we can further more explore the theory and physical process of the strong field QED effect.According to the research background and requirements above,we combine the strong field QED effect with LPI,introduce the ionization process,develop a numerical simulation program and mainly study the influence of ionization characteristics on the strong field QED effect,which is the main innovations in this paper.The main works are as follows.1.The background research on the strong field QED effect.The development of the theory,experiments and numerical simulations on the strong field QED effect is studied.We find that the numerical simulation is a necessary means in this area at present.And the deficiencies of the sexisting simulation works are summed up,then the main work of this paper is selected.In this paper we mainly study the impact of the ionization process and the density distribution on the strong field QED effect,in addition,develop a simulation program which has an independent intellectual property2.Research on PIC simulation model included the ionization effects.The realization of LPI simulation using the classical PIC method.and the optimization of the existing program BUMBLEBEE-LPI.especially the related modules of plasma formation,which contain the realization the theories and numerical simulation models of high-Z field ionization,which also satisfy energy conservation,the derivation of the complete coulomb collision theory,and the establishment of a universal numerical simulation model of electron impact ionization.3,The establishment of a strong field QED mathematical model.Firstly,the radiation energy of electron is considered as individual "photon particles".Secondly,according to the formula of electron radiation power,the key parameter ? in photon generation process has been derived.Then we can obtain the connection between the optical depth of electron or positron and photon generation probability,Finally,we can get the photon generation probability.The generation probability of positive and electron pairs is obtained using the same methods.Thus the theoretical model of strong field QED effects is established.Based on the Monte Carlo method,the generation model of Gamma ray and positron and electron is also realized.4,The coupling of the PIC code including the ionization effect and the strong field QED mathematical model.Our works mainly include writing the code of QED mathematical model,embedding,debugging and testing of code in BUMBLEBEE-LPI.In addition,the interaction between a ultrahigh intensity laser and a fully ionized aluminum foil was simulated.The strong field QED effect in LPI was observed.Finally,the theoretical model and code were verified by EPOCH ID code.5,The effects of different plasma density distributions on the strong field QED effect were studied.To investigate the effect of the density distributions on QED,we simulate four kinds of density distributions(flat,linear,exponential and logarithmic),and simple analysis was performed.There is a preliminary judgment on the effects of plasma formation on the strong field QED effect.6,The study of the effects of Coulomb collision and plasma formation on the strong field QED effect.Firstly,we study the effect of coulomb collision in high-density plasma.Then we research the effects of field ionization and electron impact ionization.