An Investigation of Harmonic Oscillation of an Ion Particle in a Non-uniform Electrostatic Field

In this study, we investigate the possibility to trap an ion particle in a non-uniform electrostatic field generated by two ionic rings, with the aim to obtain and verify general results regarding our proposition. To develop the equation of motion, we first derive the electric field generated by each ring, based on the multipole expansion technique under the azimuthally symmetrical charge distribution speculation and superposition principle. Then, we establish the equation of motion regarding the Lagrangian formalism. From the results, we observe that an ion particle can exhibit harmonic motion, if the stability condition is satisfied by an appropriate parametric setting. The results are confirmed by displacement responses and phase trajectory plots, which validate our belief in the prospect to trap an ion in an electrostatic field. Furthermore, the velocity amplitude is significantly influenced by both the charge concentration of each ring and its size.