Laser-cooled non-neutral plasma experiments at NIST

Summary form only given. We summarize the status of two laser-cooled ion plasma experiments at NIST. Both experiments use Penning traps (B=4.46 T, 6.0 T) and a rotating electric-field perturbation to confine up to 10/sup 6/ /sup 9/Be/sup +/ ions. Recent measurements of the ion correlations (Mitchell et al., Science, vol. 282, p.1291, 1998), plasma modes (Mitchell et al., Optics Express, vol.2, no.8, p.314, 1998), and solid-state ion mobility from the first experiment will be given. Progress in the 2/sup nd/ experiment on using laser-cooled /sup 9/Be/sup +/ ions to trap and sympathetically cool positrons will be discussed. We have been able to trap 0.5-mm-long, 10/sup 10/ cm/sup -3 9/Be/sup +/ ion plasmas which we think will be useful for trapping positrons. In this experiment we have also observed non-spheroidal plasma shapes due to deviations from a quadratic trapping potential. These deviations become pronounced at low rotation frequencies where the plasma is shaped like a disk.