CHARGE CLOUDS IN A BOTTLE. It is now possible to store rare ions (such as antiprotons and bare uranium) indefinitely, potentially increasing the accuracy of atomic clocks based on ions. In work to be described at next week's meeting of the American Physical Society Division of Plasma Physics in Pittsburgh, UC-San Diego and NIST researchers (Pei Huang, NIST, 303-497-3508) have developed a new technique for controlling a "non-neutral plasma," a gas made entirely of positive particles such as magnesium ions or negative particles such as electrons. Charged plasmas are often held in Penning traps, devices that use electric and magnetic fields to trap them. However, the plasma slowly loses angular momentum while rotating around such a trap, and particles eventually leak out of the trap. By introducing additional electric fields that revolve around the trap's magnetic field, the researchers effectively add angular momentum to the plasma, preventing the particles from escaping. This result may also help in the more difficult task of controlling the gases of positive and negative particles that co-exist in magnetic fusion devices. (For more information, see item and picture in the plasma meeting press release at the Physics News Preview site.)