A combined trap is a quadrupole trap to which the fields of both the Paul and the Penning traps are applied. In this paper, equations of motion for ions confined in a combined trap are derived from first principles. The equations of motion are shown to give well-understood solutions for the Paul and Penning traps in the appropriate cases before they are solved to yield the axial and radial oscillation frequencies for ions in a combined trap. The dependence of these oscillation frequencies on the applied fields is investigated. The theoretical predictions were tested in an ion trap at Imperial College using very small numbers of ions, in some cases single ions. The single-ion cases were identified by the observation of quantum jumps in the fluorescence, which is characteristic of a single ion under these conditions. The agreement between the theory and experiment is good.
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Acknowledgments We would like to thank Vivian Ng for help in performing the experiments on which this paper is based . We gratefully acknowledge the financial support of the SERC for funding this research and for supplying three of us, (D .J .B ., K .D . and D .C .W .), with maintenance grants . One of us, D .J .B ., also acknowledges the support of the National Physical Laboratory via a CASE award .
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics