RF-induced heating dynamics of non-crystallized trapped ions

TL;DR

This paper explores how radio-frequency fields cause energy transfer and heating in non-crystallized trapped ions, combining simulations and experiments to understand and control ion melting and recrystallization.

Contribution

It introduces a simplified model of rf heating energy dynamics for melted ions and validates it through experiments with calcium ions.

Findings

Rf heating rate depends mainly on rf field strength.

Experimental validation of ion melting and energy inference.

Guidelines for efficient recrystallization of melted ions.

Abstract

We investigate the energy dynamics of non-crystallized (melted) ions, confined in a Paul trap. The non-periodic Coulomb interaction experienced by melted ions forms a medium for non-conservative energy transfer from the radio-frequency (rf) field to the ions, a process known as rf heating. We study rf heating by analyzing numerical simulations of non-crystallized ion motion in Paul trap potentials, in which the energy of the ions' secular motion changes at discrete intervals, corresponding to ion-ion collisions. The analysis of these collisions is used as a basis to derive a simplified model of rf heating energy dynamics, from which we conclude that the rf heating rate is predominantly dependent on the rf field strength. We confirm the predictability of the model experimentally: Two trapped $^{40}$Ca$^{+}$ ions are deterministically driven to melt, and their fluorescence rate is used to infer the ions' energy. From simulation and experimental results, we generalize which experimental parameters are required for efficient recrystallization of melted trapped ions.