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Physica Scripta

The combined trap and some possible applications

Guozhong Li, Günther Werth

Published Dec 1, 1992• 42 citations
Publisher

Abstract

We investigate the properties of a radiofrequency (Paul)-trap with a super-imposed magnetic field (combined trap). The regions of stability are significantly larger than those for a Paul-trap for both positive and negative charged ions. As a result ions of different charge sign and large mass difference can be confined simultaneously. This may have some advantages for electron cooling of highly charged ions or for the formation of anti-hydrogen from simultaneously stored positrons and antiprotons.

DOI
10.1088/0031-8949/46/6/017

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We investigate the properties of a radiofrequency (Paul)-trap with a super-imposed magnetic field (combined trap). The regions of stability are significantly larger than those for a Paul-trap for both positive and negative charged ions. As a result ions of different charge sign and large mass difference can be confined simultaneously. This may have some advantages for electron cooling of highly charged ions or for the formation of anti-hydrogen from simultaneously stored positrons and antiprotons.
Radio-frequency (rf) Paul traps operated with multifrequency rf trapping potentials provide the ability to independently confine charged particle species with widely different charge-to-mass ratios. In particular, these traps may find use in the field of antihydrogen recombination, allowing antiproton and positron clouds to be trapped and confined in the same volume without the use of large superconducting magnets. We explore the stability regions of two-frequency Paul traps and perform numerical simulations of small samples of multispecies charged-particle mixtures of up to twelve particles that indicate the promise of these traps for antihydrogen recombination.
Radio-frequency (rf) Paul traps operated with multifrequency rf trapping potentials provide the ability to independently confine charged particle species with widely different charge-to-mass ratios. In particular, these traps may find use in the field of antihydrogen recombination, allowing antiproton and positron clouds to be trapped and confined in the same volume without the use of large superconducting magnets. We explore the stability regions of two-frequency Paul traps and perform numerical simulations of small samples of multispecies charged-particle mixtures of up to twelve particles that indicate the promise of these traps for antihydrogen recombination.
Radiofrequency (RF) traps enable highly controlled interactions between charged particles, including reactions between cold molecular ions, sympathetic cooling of one ion species with another, and quantum logic spectroscopy. However, the charge-to-mass (Q/m) selectivity of RF traps limits the range of objects that can be confined simultaneously in the same trap. Here, we confine two particles-a nanoparticle and an atomic ion-in the same radiofrequency trap although their charge-to-mass ratios differ by six orders of magnitude. The confinement is enabled by a dual-frequency voltage applied to the trap electrodes. We introduce a robust loading procedure under ultrahigh vacuum and characterize the stability of both particles. It is observed that slow-field micromotion, an effect specific to the dual-field setting, plays a crucial role for ion localization. Our results lay the groundwork for controlled interactions between diverse charged particles, regardless of the difference in their charge or mass, with applications from antimatter synthesis to the generation of macroscopic quantum states of motion.
We demonstrate the operation of a dual-frequency Paul trap and characterize its performance by storing either electrons or calcium ions while applying two quadrupole fields simultaneously which oscillate at Ωfast=2π×1.6Ω_\textrm{fast} = 2π\times 1.6Ωfast​=2π×1.6 GHz and Ωslow=2π×2Ω_\textrm{slow} = 2π\times 2Ωslow​=2π×2 MHz. The particles are loaded and stored in the trap under various conditions followed by detection employing an electron multiplier tube. We find that tens of electrons or ions can be trapped for up to ten milliseconds and a small fraction remains trapped even after hundreds of milliseconds. During dual-frequency operation we find that while the number of trapped electrons rapidly decreases with increase of the ΩslowΩ_\textrm{slow}Ωslow​ field amplitude, the number of trapped ions shows no dependence on the ΩfastΩ_\textrm{fast}Ωfast​ field amplitude as supported by our extensive numerical simulations. We aim to use a similar trap for synthesising antihydrogen from antiprotons and positrons. Accordingly, we discuss open challenges such as the co-trapping of oppositely charged species and particle trap duration.
Trapped-ion devices are being investigated for transportable applications, including the transfer of exotic charged particles between laboratories and the development of portable quantum technologies. To date, ion transport has been demonstrated only in magnetic (Penning) traps, whereas radiofrequency (Paul) traps are the predominant platform in quantum science. Here, we report the first transport of a few thousand ions confined in a linear Paul trap over distances of several kilometers, with transport durations of 15 and 45 min. These results establish a foundation for mobile trapped-ion quantum devices capable of operating while in motion and may enable the transport of exotic ions in Paul traps between experimental facilities.