Highly charged ion Coulomb crystallization in mixed strongly coupled plasmas

The investigation of highly charged ion Coulomb crystallization in mixed st rongly coupled plasmas is of interest in many areas: white dwarf astrophysi cal plasmas are believed to have very similar thermodynamic properties, col d highly charged ions can be used as an object for high precision laser spe ctroscopy of fine- and hyperfine transitions in the visible due to the abse nce of Doppler broadening and, an entirely new area of research is the pote ntial application to highly charged ion-based quantum computing schemes. We report the formation of such plasmas in a cryogenic Penning trap. These plasmas consisting of many species including Be+ and Xe44+ or Be+ and Xe15 ions, are formed at a temperature of less than 4 K. The temperatures were obtained by applying a laser-based sympathetic cooling scheme. The determin ation of the temperature and density from the laser resonance width and the fluorescence imaging of the Be+ clouds, respectively, yields a Coulomb cou pling constant for the centrifugally separated Xe plasma high enough for cr ystallization. A molecular dynamics code, developed just for this purpose, was run to clar ify the understanding of these plasmas and it was possible to show consiste ncy between experiment and simulation.