Centrifugal separation and equilibration dynamics in an   electron-antiproton plasma
  Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally-separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally-separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments. 
G.B. Andresen, M.D. Ashkezari, M. Baquero-Ruiz, W. Bertsche, P.D.   Bowe, E. Butler, C.L. Cesar, S. Chapman, M. Charlton, A....
physics.plasm-ph hep-ex physics.atom-ph