Ion crystals in a linear Paul trap

Large ion crystals containing as many as 10(5) laser-cooled Mg-24(+) ions a rranged in 10 cylindrical shells around a central string have been observed in a linear Paul trap. For smaller crystals consisting of approximately 35 00 ions, the varying linear charge densities along the trap axis give rise to well-defined transition regions between the different shell-structures. These structures and the transition regions as a function of linear density are in good agreement with molecular dynamics simulations. The micromotion of the ions in such smaller crystals is also investigated through comparis on with MD-simulations. Finally, the degree and progression of ordering in the plasma have been observed for various temperatures and compared with MD -simulations. Good qualitative agreement is again obtained.