Steady-State Confinement of Non-neutral Plasmas by Rotating Electric Fields

We apply ``rotating wall'' electric fields to spin up a non-neutral plasma in a Penning-Malmberg trap, resulting in steady-state confinement (weeks) of up to 10⁹Mg⁺ ions. The resulting ion columns can be near global thermal equilibrium, with near-uniform temperature and rotation frequency. The equilibrated plasma E×B rotation rate fE is observed to be somewhat less than the drive frequency fw, with slip Δf≡fw-fE depending on temperature as Δf∝T1/2 for 0.05T5eV. Dynamic measurements of applied torque versus slip frequency show plasma spin up and compression for Δf>0 and plasma slowing and expansion for Δf<0. By gradually increasing fw, density compression up to 20% of the Brillouin density limit has been achieved. Heating resonances and hysteresis in plasma parameters are also observed.