Chaos and Bifurcations in the Monopole Ion Trap

The monopole ion trap is based on the dynamic stabilization of a charged particle near an electric field maximum. The trap uses strong defocusing to confine the particle to a region between two concentric spherical electrodes, and this spherical geometry leads to a nonlinear equation of motion. The system has been previously studied as a periodically driven nonlinear oscillator, and numerical results suggest that a trapped particle follows a period-doubling route to chaos. In this experiment, charged polyethylene microspheres were trapped using the simultaneous application of static and alternating voltages. The microspheres were charged using the triboelectric effect and their motion was captured using a high-speed digital camera. We report the experimental observation of three bifurcations towards chaos and a period-three attractor.