Interaction of relativistic intensity laser with a compressed plasma

激光技术的迅猛发展使产生相对论等离子体成为可能。利用这一进展，在激光核聚变中提出了快速点火方案。本项目的目的是研究压缩等离子体中激光等离子体相互作用和快速点火的物理机制。首先，我们研究了利用超短脉冲加热压缩燃料边缘的打孔过程。在一个实例中，我们用大规模并行计算机求解了Vlasov-Maxwell方程组，研究了激光与等离子体的相对论相互作用物理。结果发现，自聚焦并不总是预期的，而传播的激光束由于韦伯型不稳定性而破碎。对于压缩核的点火和燃烧，我们利用二维内爆程序和α粒子输运程序，阐明了压缩核聚变增益的标度律。无论是在核中心还是在核边缘点火，都获得了几乎相同的点火条件，并且发现在兆焦耳激光照射的情况下，原则上可以获得约200的目标增益，可以用强激光设计天文现象的模型实验。这些专题与本项目有关，并在报告中作了简要说明。

Drastic progress of laser technology have made it possible to produce a relativistic plasma. By use of this advance, the fast ignition scheme has been proposed in laser fusions. The purpose of this project is to study the laser plasma interactions in a compressed plasma and to clarify the physics of fast ignition.At first, we have studied the hole boring process to guide a ultra-short pulse to heat the edge of a compressed fuel. In one case, we have studied the relativistic interaction physics of laser and plasma by solving Vlasov-Maxwell equations with massive parallel computer. As the result, it is found that the self-focusing is not always expected, while the propagating laser beam breaks up due to the Weibel-type instability. This fact is also confirmed in the study with a particle code.Concerning the ignition and burn in the compressed core, we have clarified a scaling law of fusion gain of a given compressed core by use of 2-dimensional implosion code with alpha-particle transport code. Regardless whether ignition is triggered at the core center or edge, almost the same ignition condition has been obtained, It is also found that the target gain about 200 can be obtained in principle for the case of Mega Joule laser irradiation.Model experiments of astronomical phenomena can be designed with the intense laser lights. This topics is related to the present project and is briefly described in the report.