Test Particle Diffusion In Correlated Plasmas

Inter-particle correlations have several effects on the dynamical properties of plasmas. The correlation parameter $\Gamma \equiv $ e$^{\mathrm{2}}$/aT represents the ratio of the nearest neighbor electrostatic energy to the thermal energy. We cool un-neutralized magnesium ion plasmas in a Penning-Malmberg trap, with density n $\cong $10$^{\mathrm{7}}$ cm$^{\mathrm{-3}}$, the temperature T is controlled over a wide range of 5eV \textgreater T \textgreater 5x10$^{\mathrm{-6}}$eV, resulting in correlation parameters 10$^{\mathrm{-5}}$ \textless $\Gamma $ \textless 10. We have measured the perpendicular to parallel collision rate $\nu _{\mathrm{\bot //\thinspace \thinspace }}$from the non-correlated to strongly correlated regime, and observe the (Salpeter) enhancement of $\nu _{\mathrm{\bot //\thinspace }}$ up to 10$^{\mathrm{9}}$ due to correlations [1]. We have also measured test particle diffusion and heat transport in these plasmas in the absence of correlation ($\Gamma $\textless \textless 1). Here, we propose to extend these measurements into the moderately correlated regime. In the range of 10$^{\mathrm{-3\thinspace }}$\textless $\Gamma $ \textless 1, where no experiment or numerical simulation have been done, we will test theory [2] predicting decreasing diffusion coefficient D as T decreases, with transition from D$\propto $T$^{\mathrm{-1/2}}$ to D$\propto $T and a transition from D$\propto $ B$^{\mathrm{-2}}$ to D$\propto $B$^{\mathrm{-1}}$. [1] F. Anderegg et al., PRL, 102, 185001 (2009). [2] T. Ott and M. Bonitz, PRL, 107, 135003 (2011); S.D. Baalrud and J. Daligaut, Phys. Rev. E, 96, 043202 (2017).