Correcting symmetry imperfections in linear multipole traps

TL;DR

This paper introduces a method to correct geometrical imperfections in linear multipole traps by adjusting RF amplitudes, enabling the creation of more uniform ion structures and improving trap potential quality.

Contribution

It presents a novel compensation technique for symmetry imperfections in multipole traps, enhancing the control over ion crystal topologies.

Findings

Effective correction of trap potential imperfections demonstrated

Feasibility of generating homogeneous ion ring crystals shown

Method applicable to macroscopic multipole traps for improved stability

Abstract

Multipole radio-frequency traps are central to collisional experiments in cryogenic environments. They also offer possibilities to generate new type of ion crystals topologies and in particular the potential to create infinite 1D/2D structures: ion rings and ion tubes. However, multipole traps have also been shown to be very sensitive to geometrical misalignment of the trap rods, leading to additional local trapping minima. The present work proposes a method to correct non-ideal potentials, by modifying the applied radio-frequency amplitudes for each trap rod. This approach is discussed for the octupole trap, leading to the restitution of the ideal Mexican-Hat-like pseudo-potential, expected in multipole traps. The goodness of the compensation method is quantified in terms of the choice of the diagnosis area, the residual trapping potential variations, the required adaptation of the applied radio-frequency voltage amplitudes, and the impact on the trapped ion structures. Experimental implementation for macroscopic multipole traps is also discussed, in order to propose a diagnostic method with respect to the resolution and stability of the trap drive. Using the proposed compensation technique, we discuss the feasibility of generating a homogeneous ion ring crystal, which is a measure of quality for the obtained potential well.