Properties of fast heat transport in dense plasmas under PW laser irradiation

Energy transport from laser heated region to dense plasmas is an essential issue to create high energy density plasmas, especially, in fast ignition scheme in laser fusion. The energy transport has been discussed as a process including thermal diffusion and non-local heating. Here, the thermal diffusion is the regime where the collisional mean free path l_mfp is much shorter than the temperature scale length L (l_mfp << L), while the non-local heating occurs when l_mfp >> L. However, heat transport in the intermediate regime (l_mfp ~ L) is not understood well. We recently found with collisional PIC simulations that a fast heat transport, “heatwave”, is established in a few picoseconds under a continuous irradiation of PW laser light. The heat propagates from the hot plasmas absorbing the laser energy in dense plasmas with a heat front structure different from that expected by the Spitzer-Härm diffusion model. In this talk, we will present the regime of heatwave transport, its properties, and dependence of plasma density and laser intensity, especially in relation to fast ignition of laser fusion.