快点火与超强激光等离子体相互作用问题

“快点火”是近年来提出的激光聚变点火的一种新方式。它的特点是靶丸的压缩和点火分开进行：第一步由通常的多束激光对称辐照靶丸获得高密度；而后由单束超强激光（Iλ≈10^18-20Wum^2/cm^2)加热芯部实现点火。第传统的“热斑点火）比较，快点火在压缩方面具有很多优越性：大量节省驱动能量，降低了对驱动均匀性的要求，并且可以达到更高的能量增益。但是超强激光点火却涉及一些非常复杂的问题：在预压缩形成的等郭体中打洞（hole boring)；在高密度燃料的边沿产生足够数量的高能量电子（MeV），这些电子的传输加热等。文章简短地讨论了这些问题，并研究了几十kJ激光能量实现点火的可能性。

FAST IGNITION AND ULTRAINTENSE LASER PLASMA INTERACTION

Fast ignition is a recently proposed new scheme for realizing ignition of inertial confinement fusion, in which the compression of an implosive capsule and its ignition proceed separately. First, the fusion pellet is precompressed by multiple beam lasers in the conventional way to a high density, then ignition is realized by a single ultraintense laser beam (of Iλ2≈1018—20 Wμm2／cm2). Fast ignition is superior to traditional `hot spot ignition' in many aspects in the precompression stage; it drastically reduces the energy required for precompression(about ten times), relaxes the requirement of drive uniformity, and is able to reach higher energy gain. However, ignition by ultraintense laser is very complicated. It involves boring a hole in the precompressed plasma, generating intense hot electrons with MeV energy, transporting them in the dense plasma and heating the high-density core to meet ignition conditions. These problems are briefly discussed and the possibility of ignition with laser energy less than 100kJ is explored.