A mechanism of isochoric heating of a solid density plasma by a kilojoule (kJ) class laser with relativistic intensity and a ten picosecond (ps) pulse duration is delineated by collisional Particle-in-Cell (PIC) simulations. Before an emergence of kJ class lasers, plasma heating by the laser-accelerated relativistic electron beam (REB) has been studied as the dominant isochoric heating process by intense lasers. A recent experiment using a kJ class laser indicates that the thermal diffusion from the hot plasma surface becomes the dominant process of the isochoric heating in the ps scale laser irradiation. In this article, we demonstrate that a transition of the dominant isochoric heating process from the REB heating to the thermal diffusion happens in the 10 ps laser irradiation. The diffusion heat front propagates with the speed approximately 2 μm/ps in an Aluminum target. Additionally, the hot dense plasma expands to create a steep laser-plasma interface, which is found to reduce REB energy.

通过碰撞颗粒内碰撞（PIC）模拟，描绘了由相对论强度和十皮秒（ps）脉冲持续时间的千焦（kJ）类激光对固体密度等离子体进行等速加热的机制。在出现kJ类激光器之前，已经研究了通过激光加速的相对论电子束（REB）进行的等离子体加热作为强激光的主要等速加热过程。最近使用kJ类激光器进行的实验表明，从热等离子体表面进行的热扩散成为ps规模激光照射中等色加热的主要过程。在本文中，我们证明了在10 ps激光照射中发生了从REB加热到热扩散的主要等速加热过程的转变。扩散热锋以大约2的速度传播 μ米/ PS在铝靶。另外，热的密集等离子体膨胀以产生陡峭的激光-等离子体界面，这被发现降低了REB能量。