Collective Mode Excitation by Asymmetric Fields in a Linear Paul Trap to Study Beam Stability

A second arbitrary function generator was used to apply trapping waveforms to the Paul Trap Simulator Experiment (PTSX) electrodes that do not have 90-degree-odd rotational symmetry as they do in a standard linear Paul trap. Time-oscillating transverse dipole, quadrupole, and uniform potentials were generated and their effects on the long term stability of the trapped charge bunch were studied as a function of perturbation amplitude, frequency, and duration. As expected, time-oscillating uniform potential perturbations have no effect. Dipole perturbations applied near the expected m = 1 dipole mode frequency result in strong emittance growth and particle loss. Changing the relative phase of the trap electrode waveforms also breaks the 90-degree-odd rotational symmetry and results in large amplitude particle excursions and particle loss. The results of these experiments are compared to an envelope equation model and also to the results of a particle-in-cell (WARP) code.