Chaos in the monopole ion trap

The theory and practical design of a monopole ion trapping system are presented, along with our experimental observations of nonlinear motion of a single charged polyethylene microsphere in the trap. For these observations, the trap was operated at a drive frequency of 70 Hz and easily produced voltages in the kV range. The resulting ion motion was captured using a high-speed camera acquiring images at up to 4000 frames per second. These data yielded time series, phase space portraits, and power spectra of the ion motion in a range of applied voltages, allowing us to observe a period-doubling route to chaos and a period-3 window within the chaotic regime. It is shown that these observations agree with a numerical integration of the ion's nonlinear equation of motion in the monopole electric field. (C) 2021 American Association of Physics Teachers.