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首页> 外文期刊>Plasma physics and controlled fusion >Laser-plasma interactions in direct-drive ignition plasmas
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Laser-plasma interactions in direct-drive ignition plasmas

机译：直接驱动点火等离子体中的激光等离子体相互作用

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Direct-drive ignition is most susceptible to multiple-beam laser-plasma instabilities, as the single-beam intensities are low (I_s ～ 10~(14) W cm~(-2)) and the electron temperature in the underdense plasma is high (T_e ? 3.5 keV). Cross-beam energy transfer is driven by multiple laser beams and can significantly reduce the hydrodynamic efficiency in direct-drive experiments on OMEGA (Boehly et al 1997 Opt. Commun. 133 495). Reducing the radii of the laser beams significantly increases the hydrodynamic efficiency at the cost of an increase in the low-mode modulations. Initial 2D hydrodynamic simulations indicate that zooming, transitioning the laser-beam radius prior to the main drive, does not increase low-mode nonuniformities. The combination of zooming and dynamic bandwidth reduction will provide a 30% effective increase in the drive energy on OMEGA direct-drive implosions. It was shown that two-plasmon decay (TPD) can be driven by multiple laser beams and both planar and spherical experiments were performed to study the hot electrons generated by TPD. The fraction of laser energy converted to hot electrons scales with the hot-electron temperature for all geometries and over a wide range of intensities. At ignition-relevant intensities, the fraction of laser energy converted to hot electrons is measured to decrease by an order of magnitude when the ablator material is changed from carbon-hydrogen to aluminum. The TPD results are compared with a multiple-beam linear theory and a nonlinear Zakharov model.
机译：由于单光束强度低（I_s〜10〜（14）W cm〜（-2））且低密度等离子体中的电子温度高，因此直接驱动点火最容易受到多光束激光等离子体不稳定性的影响。 （T_e≥3.5keV）。横光束能量传输由多个激光束驱动，并且在OMEGA上的直接驱动实验中会大大降低流体动力学效率（Boehly等，1997，Opt。Commun。133 495）。减小激光束的半径以增加低模调制为代价大大提高了流体动力学效率。最初的2D流体动力学模拟表明，缩放（在主驱动器之前转换激光束半径）不会增加低模不均匀性。缩放和动态带宽减少的结合将使OMEGA直接驱动内爆的驱动能量有效增加30％。结果表明，两等离子体激元衰减（TPD）可以由多个激光束驱动，并且通过平面和球形实验研究了TPD产生的热电子。激光能量转换成热电子的比例随热电子温度的变化在所有几何形状和各种强度下成比例。在与点火有关的强度下，当烧蚀剂材料从碳氢变为铝时，转换成热电子的激光能量的比例被测量降低了一个数量级。将TPD结果与多光束线性理论和非线性Zakharov模型进行比较。

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