Illustration of a Penning trap, a device that uses electric
and magnetic fields to trap charged particles (ions). The two batteries
at the two ends produce the electric field (red field lines). The magnetic
field lines (green) travel from bottom to top. In many experiments involving
Penning traps, a laser beam (blue) is used to cool the ions to very low
temperatures. In new experiments, researchers have added new electric fields
(not shown) that rotate about the magnetic field lines. These additional
field lines allow researchers to confine ions in the traps indefinitely.
(Courtesy National Institute of Standards and Technology.)
