JILA’s gold-plated ion trap for measuring the electron’s roundness, or electric dipole moment (EDM). The six “fins” in the foreground are electrodes attached to the trap’s lower endcap. When assembled, the trap is placed in a vacuum chamber and the electrodes are charged with up to 100 volts to confine hafnium fluoride ions (charged molecules). Researchers rotate electric and magnetic fields fast enough to trap the molecular ions but slowly enough for the ions to line up with the electric field. The ions then rotate individually while scientists measure their properties. The EDM is the difference between two magnetic energy levels.