Blackett Laboratory, Imperial College London, London, SW7 2BZ, United Kingdom.
Phys Rev Lett. 2010 Aug 27;105(9):095001. doi: 10.1103/PhysRevLett.105.095001. Epub 2010 Aug 24.
Experiments where a laser-generated proton beam is used to probe the megagauss strength self-generated magnetic fields from a nanosecond laser interaction with an aluminum target are presented. At intensities of 10(15) W cm(-2) and under conditions of significant fast electron production and strong heat fluxes, the electron mean-free-path is long compared with the temperature gradient scale length and hence nonlocal transport is important for the dynamics of the magnetic field in the plasma. The hot electron flux transports self-generated magnetic fields away from the focal region through the Nernst effect [A. Nishiguchi, Phys. Rev. Lett. 53, 262 (1984)] at significantly higher velocities than the fluid velocity. Two-dimensional implicit Vlasov-Fokker-Planck modeling shows that the Nernst effect allows advection and self-generation transports magnetic fields at significantly faster than the ion fluid velocity, v(N)/c(s)≈10.
实验中使用激光产生的质子束来探测纳秒激光与铝靶相互作用产生的兆高斯强度自生成磁场。在 10(15)W/cm(-2)的强度下，伴随着大量快电子的产生和强热通量，电子平均自由程相比于温度梯度尺度长度很长，因此非局域输运对于等离子体中磁场的动力学非常重要。热电子流通过能斯特效应（A. Nishiguchi，Phys. Rev. Lett. 53, 262 (1984)）以比流体速度高得多的速度将自生成的磁场从焦点区域输运出去。二维隐式的 Vlasov-Fokker-Planck 模型表明，能斯特效应允许磁场的平流和自生成输运速度比离子流体速度快得多，v(N)/c(s)≈10。
