Abstract
In this paper we present the first quantitative measurement of the change in frequency (tune) with intensity of four transverse resonances in a high intensity Gaussian beam. Due to the nonlinear space charge forces present in high intensity beams, particle motion cannot be analytically described. Instead we use the simulator of particle orbit dynamics and the intense beam experiment, two linear Paul traps (LPTs), to replicate the system experimentally. In high intensity beams a coherent resonant response to both space charge and external field driven perturbations is possible, these coherent resonances are excited at a tune that differs by a factor Cm from that of the incoherent resonance. By increasing the number of ions stored in the LPT and studying the location of four different resonances we extract provisional values describing the change in tune of the resonance with intensity. These values are then compared to the Cm factors for coherent resonances. We find that the Cm factors do not accurately predict the location of resonances in high intensity Gaussian beams. Further insight into the experiment was gained through simulation using Warp, a particle-in-cell code.
Highlights
High intensity particle accelerators are vital in many applications, from spallation neutron sources to the transmutation of nuclear waste
This paper presents the first quantitative study of the interaction and difference between coherent and incoherent resonances in a Paul trap, and uses simulation to explain why the experimental results differ from those theoretically predicted
We extract numerical values describing the locations of resonances at high intensity
Summary
High intensity particle accelerators are vital in many applications, from spallation neutron sources to the transmutation of nuclear waste. In reference [17] Ohtusubo et al applied a quadrupole error to the S-POD trap to excite resonances and ion loss was studied at three different intensities They qualitatively draw the conclusion that the Cm factors for m = 2, m = 3 and m = 4. We do not apply any external error fields to the trap, resonances are either driven by space charge forces or by small multipole fields from slight trap misalignments and in the high intensity regime in which this experiment is conducted space charge driven resonances dominate [17] From this data we extracted a numerical value for the location of four resonances of different orders at different ion numbers.
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