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arXiv · 2012.08198

An analytical approach to symmetry breaking in multipole RF-traps

Marylise Marchenay·Jofre Pedregosa-Gutierrez·Martina Knoop·Marie Houssin·Caroline Champenois
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Abstract

Radio-frequency linear multipole traps have been shown to be very sensitive to mis-positioning of their electrodes, which results in a symmetry breaking and leads to extra local minima in the trapping potential \cite{pedregosa17} disturbing the operation of the trap. In this work, we analytically describe the RF-potential of a realistic octupole trap by including lower order terms to the well-established equation for a perfectly symmetric octupole trap. We describe the geometry by a combination of identified defects, characterised by simple analytical expressions. A complete equation is proposed for a trap with any electrode deviation relying on a combination of the simple cases where the defects are taken individually. Our approach is validated by comparison between analytical and numerical results for defect sizes up to 4\% of the trap radius. As described in \cite{pedregosa18}, an independent fine-tuning of the amplitude of the RF voltage applied on each electrode can be used to mitigate the geometrical defects of a realistic trap. In a different way than in \cite{pedregosa18}, the knowledge of an analytical equation for the potential allows to design the set of RF-voltages required for this compensation, based on the experimental measurement of the ion position in the trap, without information concerning the exact position of each electrode, and with a small number of iterations. The requirements, performances and limitations of this protocol are discussed via comparison of numerical simulations and analytical results.

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Marylise Marchenay, Jofre Pedregosa-Gutierrez, Martina Knoop, Marie Houssin, Caroline Champenois. 2020-12-15. An analytical approach to symmetry breaking in multipole RF-traps. https://arxiv.org/abs/2012.08198

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