Title: Symmetry breaking in linear multipole traps,
Abstract: Radiofrequency multipole traps have been used for some decades in cold
collision experiments, and are gaining interest for precision spectroscopy due
to their low mi-cromotion contribution, and the predicted unusual cold-ion
structures. However, the experimental realisation is not yet fully controlled,
and open questions in the operation of these devices remain. We present
experimental observations of symmetry breaking of the trapping potential in a
macroscopic octupole trap with laser-cooled ions. Numerical simulations have
been performed in order to explain the appearance of additional local potential
minima, and be able to control them in a next step. We characterize these
additional potential minima, in particular with respect to their position,
their potential depth and their probability of population as a function of the
radial and angular displacement of the trapping rods.