Mev x-ray and position generation by ultra intense lasers

研究了短脉冲超强激光与固体靶的粒子相互作用，并进行了计算机模拟和理论分析。利用所安装的激光装置，研究了相对论等离子体的MeV X射线能谱。在计算机模拟中，我们阐明了在10^&lt；18；-10^&lt；19&gt；w/cm^2辐照强度下，激光在固体靶上产生的等离子体发射出少量MeV电子和离子。我们还发现，当激光强度大于10^&lt；19；w/cm2时，这些高能电子的能谱可达10 MeV。模拟还表明，产生了高于10^9高斯的超强磁场。至于这种强磁场的产生机制，我们发现其机制与两个流不稳定性(或称魏贝尔不稳定性)密切相关。强磁场的产生影响MeV X射线和正电子的产生。还发展了二维模拟，并用于研究聚焦强激光光斑周围的电磁现象。通过这些模拟，研究了高密度等离子体中的高能电子弛豫、MeV X射线再生和电子-正电子对的产生。最后，我们意识到上述结果将有助于理解活动星系核附近的相对论等离子体现象。

Investigated are the interactions of short pulse ultra intense lasers with solid targets by a particle in cell computer simulation code and theoretical analysis. MeV x-ray spectra from relativistic plasmas are also investigated by using the laser facilities which are installed in the institute. In the computer simulation, we clarified that with 10^<18>-10^<19>w/cm^2 irradiation intensity, laser produced plasmas on solid targets emit a few MeV electrons and ions. We also found that the energy spectrum of those high energy electron reaches several 10 MeV when the laser intensity is higher than 10^<19>w/cm^2.The simulations show also that ultra strong magnetic field higher than 10^9 Gauss is generated. As for the generation mechanism of this strong magnetic field, it is found that the mechanism is closely related to the two stream instabilities (or Weibel instability). The generation of strong magnetic field effects the MeV x-ray and positron generations.The two dimensional simulation was also developed and used for studying the electro-magnetic phenomena around focused intense laser spot. By those simulations, high energy electron relaxation in dense plasmas, MeV x-ray reneration and electron-positron pair creation are investigated. The results are compared with recent experimental results to find future research issues.Finally, we realized that the above results will be useful for understanding the relativistic plasma phenomena near active galactic nuclear.