Ion acceleration via plasma turbulence and collisionless shock generation

近年来，高功率激光设备取得了前所未有的进步。这样，激光与物质的相互作用就进入了实验室天体物理学感兴趣的参数区域。特别是，相对论短强度激光与物质的相互作用可以产生一些高能量密度态(HED)。例如，当激光产生的强流电子束通过韦伯不稳定性在固体靶中传输时，可以形成磁性湍动等离子体；当强激光脉冲与气体或固体密度等离子体相互作用时，可以产生高能的强流电子束和离子束。这种不稳定性被广泛认为是天体(例如伽马射线爆发、脉冲星风、活动星系核)中相对论外流的物理学基础，特别是作为产生非热高能粒子和辐射的无碰撞冲击波的来源。高功率激光等离子体实验可以产生具有高能量密度的独特参数区域，而数值模拟可以在高性能计算机上提供复杂动态系统的各种信息，这些信息可以在实验中测量。在这个项目中，我们将用强激光与固体的相互作用来模拟魏贝尔型的磁湍流。以前的模拟都是空间分辨率低、时间有限、限于二维几何形状，不能直接与实验观测进行比较。有了我们的新程序，磁等离子体湍流将在3D中更准确地建模，从而可以与实验进行直接比较。我们将集中讨论在不同强度的激光脉冲照射下相对论热电子的正向电流和背景电子的冷返回电流之间的微观过程，如韦贝尔不稳定性和两个流不稳定性，以及随后在几十皮秒的时间尺度上磁湍流的发展。动力学PIC模拟将得到磁场的时间演化和空间分布(k谱的幂定律)。

High-power laser facilities have made unprecedented progress in recent years. With this the laser-matter interaction has entered parameter regimes of interest for laboratory astrophysics. In particular, the interactions of relativistic short intense lasers with matter can generate some high energy density states (HEDS). For example, magnetic turbulent plasmas can be formed while laser produced high current electron beams transport in solid targets via Weibel instability, and high-energy high-current electron and ion beams can be produced while intense laser pulses interact with gas or solid density plasmas. This instability is widely thought to underpin the physics of relativistic outflows in astrophysical objects (e.g., gamma-ray bursts, pulsar winds, active galactic nuclei), especially as the source of the collisionless shock waves responsible for generating nonthermal high-energy particles and radiations. High-power laser plasma experiments can produce unique parameter regimes with high energy density, while numerical simulations can provide a great variety of information of complex and dynamic systems with high performance computers, which may be measured in experiments. In this project, Weibel-type magnetic turbulence will be modelled by intense laser solid interactions. Previous simulations have been carried out with low spatial resolutions, limited time and limited to 2D geometry, which cannot be compared directly to experimental observation. With our new code, magnetic plasma turbulence will modelled more accurately in 3D, so that direct comparison with experiments could be made. We shall focus on the micro-processes, like Weibel instabilities and two stream instabilities between forward currents of relativistic hot electrons and cold return currents of background electrons under the irradiance of laser pulses under different intensities, and the subsequent development of magnetic turbulence over the time scale of a few tens of picosecond. The temporal evolution and spatial profiles (power law of k spectra) of magnetic fields will be obtained by kinetic PIC simulations.