Higashi Naoki, Iwata Natsumi, Sano Takayoshi, Mima Kunioki, Sentoku Yasuhiko
Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikanecho, Toyonaka, Osaka 560-0043, Japan.
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
Phys Rev E. 2022 May;105(5-2):055202. doi: 10.1103/PhysRevE.105.055202.
The interaction of relativistic short-pulse lasers with matter produces fast electrons with over megaampere currents, which supposedly heats a solid target isochorically and forms a hot dense plasma. In a picosecond timescale, however, thermal diffusion from hot preformed plasma turns out to be the dominant process of isochoric heating. We describe a heating process, fast thermal diffusion, launched from the preformed plasma heated resistively by the fast electron current. We demonstrate the fast thermal diffusion in the keV range in a solid density plasma by a series of one-dimensional particle-in-cell simulations. A theoretical model of the fast thermal diffusion is developed and we derive the diffusion speed as a function of the laser amplitude and target density. Under continuous laser irradiation, the diffusion front propagates at a constant speed in uniform plasma. Our model can provide a guideline for fast isochoric heating using future kilojoule petawatt lasers.
相对论短脉冲激光与物质的相互作用产生了具有兆安以上电流的快速电子，这些电子据推测会等容加热固体靶并形成热致密等离子体。然而，在皮秒时间尺度上，来自热预形成等离子体的热扩散结果成为等容加热的主导过程。我们描述了一种加热过程，即快速热扩散，它由被快速电子流电阻加热的预形成等离子体引发。我们通过一系列一维粒子模拟展示了在固体密度等离子体中keV范围内的快速热扩散。建立了快速热扩散的理论模型，并推导出扩散速度作为激光振幅和靶密度的函数。在连续激光照射下，扩散前沿在均匀等离子体中以恒定速度传播。我们的模型可为未来使用千焦拍瓦激光器进行快速等容加热提供指导。
