Application of high-power lasers to study matter at ultrahigh pressures

Abstract

This article reviews the current status of studies by means of lasers of superdense nonideal plasmas. The main attention is paid to laser methods of generating plane steady-state shock waves with extremely high pressures. The role is discussed of various factors that complicate the design of laser experiments: generation of high-energy non-Maxwell electrons, plasma and hydrodynamic instabilities, restrictions on heat flux, etc. The advantages are pointed out of using highfrequency lasers and layered targets to obtain a plasma with extremal parameters.

Effect of thermal conductivity on the Knudsen layer at ablative surfaces

“…This is the case for the example in [9], where an externally applied laser radiation source heats the ablating surface but for which the gas (plasma) is transparent.…”

“…Anisimov [9] was the first to consider details of the vaporization process for a case of vaporization of a metal exposed to laser radiation. He used a bimodal velocity distribution function in the kinetic layer, assuming no absorption of laser radiation in the ablated gas.…”

“…It should be noted that the Anisimov's model [9] (as well as all other existing models) employed shifted Maxwellian function at the outer boundary of Knudsen Layer ignoring, as mentioned above, the conduction heat transfer to the ablative surface, i.e. temperature gradient at the edge of the Knudsen layer.…”

“…Assuming the conservation laws of mass, momentum and energy hold at all times within the discontinuity region, through the Knudsen layer, as it has been assumed in all previous models [9][10][11][12][13][14] (quasi steady state approximation within the Knudsen layer), the following integrals are defined:…”

“…Thus, our model is limited to relatively small values of the temperature gradients. Following Anisimov's method [9], let us write the velocity distribution function in the kinetic layer with the evaporating surface in the form, Fig.1 [ ]…”