@article{Otto_2009,
	doi = {10.1088/0953-4075/42/15/154007},
	url = {https://doi.org/10.1088/0953-4075/42/15/154007},
	year = 2009,
	month = {jul},
	publisher = {{IOP} Publishing},
	volume = {42},
	number = {15},
	pages = {154007},
	author = {R Otto and P Hlavenka and S Trippel and J Mikosch and K Singer and M Weidemüller and R Wester},
	title = {How can a 22-pole ion trap exhibit ten local minima in the effective potential?},
	journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
	abstract = {The column density distribution of trapped OH− ions in a 22-pole ion trap is measured for different trap parameters. The density is obtained from position-dependent photodetachment rate measurements. Overall, agreement is found with the effective potential of an ideal 22-pole. However, in addition, we observe ten distinct minima in the trapping potential, which indicate a breaking of the 22-fold symmetry. Numerical simulations show that a displacement of a subset of the radiofrequency electrodes can serve as an explanation for this symmetry breaking.}
}