Theoretic Study On The Interaction Of Ultra-Intense Pulse Laser With High Temperature Plasmas And Deuterium Clusters

The present thesis is firstly devoted to the dynamic behavior of relativistic electrons in the high-temperature plasma. First of all, we have developed an approach to fix the Lorentz factor of particles in the system. The interactions between relativistic electrons in high-temperature plasma are analyzed theoretically. By splitting the electron density fluctuations into the individual part and the collective part, we mainly study the collective oscillation of the relativistic electrons resulting from the electromagnetic interactions. Consequently, we derive the frequency of the high-temperature plasma and the "Debye length" with relativistic modification. Secondly, considering the Coulomb-hydrodynamic explosion induced by the interaction between a deuterium cluster target and ultra-intensity femtosecond laser, the mechanism which generates energetic deuterium nuclei for the fusion has been analyzed. The formulas for expansions of deuterium ion cluster, which are driven by Coulomb-hydrodynamic explosion, are proposed; and hence the kinetic energies of deuterium nuclei, the expansion time and exploding efficiency of deuterium ion cluster have been estimated. Finally, in muon-catalyed fusion, the influence of laser fields on μ~3He muonic atom ionization is studied.The main results are as follows:(1). The collective behavior of relativistic electrons in the hot plasma, (a) For the relativistic plasma, how to fix the Lorentz factor of particles in the system is an important problem, we resolve this problem by demonstrating the exact relation between average Lorentz factor and temperature in relativistic plasmas. A rather simple relation is also obtained for the ultra-relativistic case, (b) By introducing the Lienard-Weichert potential for the relativistic electrons and splitting the electron density fluctuations into the individual part and the collective part, we study the collective oscillation of the relativistic electrons resulting from the electromagnetic interactions. Consequently, we derive the oscillation frequency of the hot plasma and the "Debye length" with the relativistic modification. We show that the increase of the plasma temperature, as well as that of the velocity of the electrons, leads to thedecrease of the plasma frequency and the increase of the "Debye length". Moreover, this trend becomes more obvious when the plasma temperature is higher, (c) We study the energy loss of a fast-electron beam due to the excitation of the collective oscillation in the hot plasma. It is shown that the energy loss based on the relativistic modified with increase in the hot plasma temperature the difference becomes more obvious. In a dense electron gas, we know that for phenomena involving distances greater than the Debye length, the system behaves collectively; for distances shorter than this length, it may be treated as a collection of approximately free individual particles. For the hot plasma with the same electron density, the increase of the "Debye length" causes the decrease in the number of the electrons participating in the random thermal motion. Therefore, in the hot plasma, the energy loss based on the relativistic modified collective excitation becomes smaller than that based on the conventional one.(2). Researches on the interactions between clusters and intense femtosecond laser pulse have recently been a hot field. Atomic clusters formed in supersonic expansion of a high-pressure gas into vacuum have been proposed recently as an alternative solution combining the advantaged of both gaseous and solid targets. For instance, recent experiments on clusters irradiated by intense laser pulses have revealed several extremely high-energetic phenomena not encountered in previous experiments restricted to atoms and small molecules: efficient generation of highly charged atomic ions, generation of keV electrons and very energetic ions with MeV kinetic energies, and emission of intense x-ray. Meanwhile clusters are considered as bridge systems between isolated molecules and the condensed matter. Based on the production of high-ion-temperature plasmas, table-top nuclear fusion from explosions of intense femtosecond laser-heated deuterium clusters is realized. We have divided small deuterium clusters expansion into two stages when the clusters are irradiated by an intense femtosecond laser pulse. The first stage is mainly the hydrodynamic expansion during unbound electrons moving out the cluster. The time of electrons escaping from the cluster is so short that the cluster expansion time and size can be neglected, but the ion energy in the expansion stage is considerable, thereby, this expansion stage make provision for the next stage. The second stage is pure Coulomb...