Long ion mean-free path and nonequilibrium radiation effects on high-aspect-ratio laser-driven implosions

The implosion dynamics of experiments with high-aspect-ratio laser-driven targets are re-examined by taking account of long ion-mean-free paths. The mean-free path is found to be comparable to the fuel size and this can cause a significant departure from a fluid-like description. One of such effects stemming from the long ion-mean-free path; namely, real viscosity, seriously changes the results; the compression ratio becomes 5 times smaller with this real viscosity. In addition to this, inclusion of non-LTE (local thermodynamic equilibrium) atomic process is shown to critically determine the implosion dynamics because of bound-free opacity associated with a small fraction of hydrogen-like ions. (author)