Nonlinear Resonances of Laser Cooled Ions in a Linear Paul Trap due to the Anharmonicity of the Trap Potential

The anharmonicity of the trap potential influences the motion of trapped and laser-cooled ions. The magnitudes of higher-order components of the trap potential depend on the electrode geometry. In this paper we provide a numerical study of the anharmonicity of linear Paul trap potentials with different electorode geometies. We have also experimentally observed nonlinear resonances of laser-cooled ions, and have studied the effect of anharmonicity in three types of liner Paul trap that have different distances between electrodes.