Early time dynamics of strongly coupled ultracold neutral Ca$^+$ and Ca$^{2+}$ plasmas

Ultracold neutral plasmas are generated by photoionizing laser-cooled atoms. Due to their extremely low temperatures, ultracold plasmas fall into the ``strongly coupled'' regime, where strong coupling is characterized by the parameter $\Gamma$. This dimensionless parameter, given by the ratio of the Coulomb potential energy to the average kinetic energy of the ions, describes the complete thermodynamic state of a strongly coupled system. This makes it possible to study the fundamental behavior of strongly coupled systems as manifested in high energy-density plasmas using low energy table-top experiments. We report progress on an experiment in laser-cooled calcium designed to increase the strong coupling of an ultracold neutral plasma by promoting the plasma ions to the second ionization state. Measurements of the effect that the Ca$^{2+}$ ions have on the temperature of the Ca$^+$ ions as a function of the second ionization fraction are discussed.