Dynamics of a single ion in a perturbed Penning trap. Sextupolar perturbation J. P. Salas, M. Iñarrea and A. I. Pascual Eur. Phys. J. D, 20 1 (2002) 45-54 Published online: 28 June 2002 DOI: 10.1140/epjd/e2002-00122-3