Thermal conductivity and viscosity in fully ionized multiple-charged strongly coupled plasma

We present the results of calculations of the thermal conductivity and viscosity coefficients for a two-component fully ionized classical Coulomb plasma having ion charges from one to three, performed by the molecular dynamics method. The model of ultracold plasma was used, where particles interact according to the Coulomb law without any restrictions at large or small distances. The calculations are carried out in a wide range of the strong coupling parameter. Similarity for the coefficients of thermal conductivity and viscosity at multiple ionization is demonstrated. Comparison with the results of calculations for other plasma models is given. The results obtained can be used for any classical non-degenerate strongly coupled plasma.

Ultrafast electron cooling in an expanding ultracold plasma

Plasma dynamics critically depends on density and temperature, thus well-controlled experimental realizations are essential benchmarks for theoretical models. The formation of an ultracold plasma can be triggered by ionizing a tunable number of atoms in a micrometer-sized volume of a 87Rb Bose-Einstein condensate (BEC) by a single femtosecond laser pulse. The large density combined with the low temperature of the BEC give rise to an initially strongly coupled plasma in a so far unexplored regime bridging ultracold neutral plasma and ionized nanoclusters. Here, we report on ultrafast cooling of electrons, trapped on orbital trajectories in the long-range Coulomb potential of the dense ionic core, with a cooling rate of 400 K ps−1. Furthermore, our experimental setup grants direct access to the electron temperature that relaxes from 5250 K to below 10 K in less than 500 ns.