Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Applied Physics

Trapping and sympathetic cooling of Th3+ ions in a linear ion trap

Zi Li, Wen-Ting Gan, Chen Wang, Lin Li, Xia Hua, Xin Tong

Published Dec 9, 2025• 1 citation
Publisher

Abstract

We demonstrate a modified integration of a linear ion trap with a time-of-flight mass spectrometer optimized to enhance the loading and detection of Th3+ ions. A phase-locked radiofrequency/high-voltage switch incorporating zero-crossing triggering and a programmable time delay is a key upgrade to minimize RF phase-dependent jitter and enable the unambiguous identification of Th3+ ions. To enhance purity, yield, and lifetime of trapped Th3+ ions, we optimize the ion loading parameters, including ion trap settings (RF amplitude, endcap voltages, and loading time), laser-ablation pulse energy, helium partial pressure, and ion storage time. These improvements extend trapping lifetimes of Th3+ ions to several hundred seconds, representing an order-of-magnitude increase compared to our previous work. Finally, single-pulse ablation of mixed Sr–Th nitrate targets enables the direct co-loading of Th3+ and 88Sr+ ions, and subsequent laser cooling forms multi-component Coulomb crystals for laser spectroscopy of Th3+ ions. Given the long trapping lifetime of Th3+ ions, this system will serve as a platform for developing a prototype trap-based thorium nuclear clock.

DOI
10.1063/5.0300192

Related papers

Trapping triply ionized thorium isotopes

Layne Churchill

Cold trapped ions have many applications in quantum information science and precision metrology. In this thesis, we present progress toward two objectives involving ions confined to linear RF traps: the strong coupling of Ba+ ions with a high finesse optical cavity, and the observation of an optical nuclear transition in 229Th3+. In pursuit of the first objective, a novel high-temperture vapor cell for the spectroscopy of neutral barium was constructed. Using this vapor cell, a new technique for isotope-selective photoionization loading of Ba+ in an ion trap was developed. In pursuit of the second objective, techniques ultimately to be used in creating, trapping, and observing 229Th3+ are studied using 232Th3+. Ion traps are loaded with 232Th3+ via laser ablation of thorium targets. 232Th3+ is detected optically using laser-induced fluorescence and electronically using a channel electron multiplier. A technique for creating ablation targets from trace quantities of thorium nitrate is presented. The primary loss mechanisms of Th3+, charge exchange and chemical reactions, are studied.

•Aug 3, 2010•4 citations

Sympathetic cooling of trapped Th3+ alpha-recoil ions for laser spectroscopy

G. Zitzer, Johannes Tiedau, Maksim V. Okhapkin +5 more

The authors experimentally demonstrate the sympathetic cooling of Th${}^{3+}$ ions, captured from uranium alpha-recoil sources, in a linear Paul trap using laser-cooled ${}^{88}$Sr${}^{+}$ ions. They show the efficacy of their method via high-resolution laser spectroscopy. This demonstration is an important step in enabling the use of these ions as the reference of a highly accurate nuclear optical clock.

arXiv:2312.05106•Physical Review A•Mar 22, 2024•12 citations

Barium ion cavity qed and triply ionized thorium ion trapping

Adam V. Steele

Trapped cold ions are tools which we used to approach two very disparate areas of physics, strong coupling between Ba+ ions and optical resonators, and investigations of a low-energy nuclear isomer of 229-Th. The first part of this thesis describes our progress towards the integration of a miniature Paul (rf) ion trap with a high finesse (F=30000) optical cavity. Ba+ ions were trapped and cooled for long periods and a new scheme for isotope selective photoionization was developed. The second part of this thesis describes our progress towards controlled excitation of the low energy nuclear isomer of 229-Th, which may provide a bridge between the techniques of cold atomic and nuclear physics. As a step towards this goal, 232-Th3+ ions were confined in rf ions traps and cooled via collisions with a buffer gas of helium. A sophisticated scanning program was developed for controlling ion trap loading, tuning lasers, and running a CCD camera to look for fluorescence. The low-lying electronic transitions of Th3+ at 984 nm, 690 nm and 1087 nm were observed via laser fluorescence.

•Nov 17, 2008•7 citations

Production of cold barium monohalide ions

De Palatis, V Michael

Ion traps are an incredibly versatile tool which have many applications throughout the physical sciences, including such diverse topics as mass spectrometry, precision frequency metrology, tests of fundamental physics, and quantum computing. In this thesis, experiments are presented which involve trapping and measuring properties of Th³⁺. Th³⁺ ions are of unique interest in part because they are a promising platform for studying an unusually low-lying nuclear transition in the 229Th nucleus which could eventually be used as an exceptional optical clock. Here, experiments to measure electronic lifetimes of Th³⁺ are described. A second experimental topic explores the production of sympathetically cooled molecular ions. The study of cold molecular ions has a number of applications, some of which include spectroscopy to aid the study of astrophysical objects, precision tests of quantum electrodynamics predictions, and the study of chemical reactions in the quantum regime. The experiments presented here involve the production of barium monohalide ions, BaX⁺ (X = F, Cl, Br). This type of molecular ion proves to be particularly promising for cooling to the rovibrational ground state. The method used for producing BaX⁺ ions involves reactions between cold, trapped Ba⁺ ions and neutral gas phase reactants at room temperature. The Ba⁺ ion reaction experiments presented in this thesis characterize these reactions for producing Coulomb crystals composed of laser cooled Ba⁺ ions and sympathetically cooled BaX⁺ ions.

•Aug 20, 2013•0 citations

An ion trap time-of-flight mass spectrometer with high mass resolution for cold trapped ion experiments

Philipp Christoph Schmid, J. M. Greenberg, Mikhail I. Miller +2 more

Trapping molecular ions that have been sympathetically cooled with laser-cooled atomic ions is a useful platform for exploring cold ion chemistry. We designed and characterized a new experimental apparatus for probing chemical reaction dynamics between molecular cations and neutral radicals at temperatures below 1 K. The ions are trapped in a linear quadrupole radio-frequency trap and sympathetically cooled by co-trapped, laser-cooled, atomic ions. The ion trap is coupled to a time-of-flight mass spectrometer to readily identify product ion species and to accurately determine trapped ion numbers. We discuss, and present in detail, the design of this ion trap time-of-flight mass spectrometer and the electronics required for driving the trap and mass spectrometer. Furthermore, we measure the performance of this system, which yields mass resolutions of m/Δm ≥ 1100 over a wide mass range, and discuss its relevance for future measurements in chemical reaction kinetics and dynamics.

arXiv:1707.07036•Review of Scientific Instruments•Dec 1, 2017•48 citations

Sympathetic cooling in a multi-isotope Sr+Coulomb crystal

S. Removille, Quentin C. Glorieux, T. Coudreau +3 more

This paper reports on trapping and laser-cooling of singly-ionized strontium ions in a linear Paul trap. We demonstrate loading of large ion clouds containing as much as 106 ions and laser cooling down to the Coulomb crystal transition. We observe the spatial segregation of the different Sr+ isotopes due to the mass-dependent Paul trap stiffness. Sympathetic cooling of the different isotopes is demonstrated, either by laser-cooling of 88Sr+ (83% abundance) or of 86Sr+ (10% abundance). These demonstrations open the way to the use of a large ion Coulomb crystal for quantum optics and quantum information experiments, where the strong confinement, the long lifetime, and the absence of perturbation by cooling lasers are crucial.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 30, 2010•1 citation
We demonstrate a modified integration of a linear ion trap with a time-of-flight mass spectrometer optimized to enhance the loading and detection of Th3+ ions. A phase-locked radiofrequency/high-voltage switch incorporating zero-crossing triggering and a programmable time delay is a key upgrade to minimize RF phase-dependent jitter and enable the unambiguous identification of Th3+ ions. To enhance purity, yield, and lifetime of trapped Th3+ ions, we optimize the ion loading parameters, including ion trap settings (RF amplitude, endcap voltages, and loading time), laser-ablation pulse energy, helium partial pressure, and ion storage time. These improvements extend trapping lifetimes of Th3+ ions to several hundred seconds, representing an order-of-magnitude increase compared to our previous work. Finally, single-pulse ablation of mixed Sr–Th nitrate targets enables the direct co-loading of Th3+ and 88Sr+ ions, and subsequent laser cooling forms multi-component Coulomb crystals for laser spectroscopy of Th3+ ions. Given the long trapping lifetime of Th3+ ions, this system will serve as a platform for developing a prototype trap-based thorium nuclear clock.
Cold trapped ions have many applications in quantum information science and precision metrology. In this thesis, we present progress toward two objectives involving ions confined to linear RF traps: the strong coupling of Ba+ ions with a high finesse optical cavity, and the observation of an optical nuclear transition in 229Th3+. In pursuit of the first objective, a novel high-temperture vapor cell for the spectroscopy of neutral barium was constructed. Using this vapor cell, a new technique for isotope-selective photoionization loading of Ba+ in an ion trap was developed. In pursuit of the second objective, techniques ultimately to be used in creating, trapping, and observing 229Th3+ are studied using 232Th3+. Ion traps are loaded with 232Th3+ via laser ablation of thorium targets. 232Th3+ is detected optically using laser-induced fluorescence and electronically using a channel electron multiplier. A technique for creating ablation targets from trace quantities of thorium nitrate is presented. The primary loss mechanisms of Th3+, charge exchange and chemical reactions, are studied.
The authors experimentally demonstrate the sympathetic cooling of Th3+{}^{3+}3+ ions, captured from uranium alpha-recoil sources, in a linear Paul trap using laser-cooled 88{}^{88}88Sr+{}^{+}+ ions. They show the efficacy of their method via high-resolution laser spectroscopy. This demonstration is an important step in enabling the use of these ions as the reference of a highly accurate nuclear optical clock.
Trapped cold ions are tools which we used to approach two very disparate areas of physics, strong coupling between Ba+ ions and optical resonators, and investigations of a low-energy nuclear isomer of 229-Th. The first part of this thesis describes our progress towards the integration of a miniature Paul (rf) ion trap with a high finesse (F=30000) optical cavity. Ba+ ions were trapped and cooled for long periods and a new scheme for isotope selective photoionization was developed. The second part of this thesis describes our progress towards controlled excitation of the low energy nuclear isomer of 229-Th, which may provide a bridge between the techniques of cold atomic and nuclear physics. As a step towards this goal, 232-Th3+ ions were confined in rf ions traps and cooled via collisions with a buffer gas of helium. A sophisticated scanning program was developed for controlling ion trap loading, tuning lasers, and running a CCD camera to look for fluorescence. The low-lying electronic transitions of Th3+ at 984 nm, 690 nm and 1087 nm were observed via laser fluorescence.
Ion traps are an incredibly versatile tool which have many applications throughout the physical sciences, including such diverse topics as mass spectrometry, precision frequency metrology, tests of fundamental physics, and quantum computing. In this thesis, experiments are presented which involve trapping and measuring properties of Th³⁺. Th³⁺ ions are of unique interest in part because they are a promising platform for studying an unusually low-lying nuclear transition in the 229Th nucleus which could eventually be used as an exceptional optical clock. Here, experiments to measure electronic lifetimes of Th³⁺ are described. A second experimental topic explores the production of sympathetically cooled molecular ions. The study of cold molecular ions has a number of applications, some of which include spectroscopy to aid the study of astrophysical objects, precision tests of quantum electrodynamics predictions, and the study of chemical reactions in the quantum regime. The experiments presented here involve the production of barium monohalide ions, BaX⁺ (X = F, Cl, Br). This type of molecular ion proves to be particularly promising for cooling to the rovibrational ground state. The method used for producing BaX⁺ ions involves reactions between cold, trapped Ba⁺ ions and neutral gas phase reactants at room temperature. The Ba⁺ ion reaction experiments presented in this thesis characterize these reactions for producing Coulomb crystals composed of laser cooled Ba⁺ ions and sympathetically cooled BaX⁺ ions.
Trapping molecular ions that have been sympathetically cooled with laser-cooled atomic ions is a useful platform for exploring cold ion chemistry. We designed and characterized a new experimental apparatus for probing chemical reaction dynamics between molecular cations and neutral radicals at temperatures below 1 K. The ions are trapped in a linear quadrupole radio-frequency trap and sympathetically cooled by co-trapped, laser-cooled, atomic ions. The ion trap is coupled to a time-of-flight mass spectrometer to readily identify product ion species and to accurately determine trapped ion numbers. We discuss, and present in detail, the design of this ion trap time-of-flight mass spectrometer and the electronics required for driving the trap and mass spectrometer. Furthermore, we measure the performance of this system, which yields mass resolutions of m/Δm ≥ 1100 over a wide mass range, and discuss its relevance for future measurements in chemical reaction kinetics and dynamics.
This paper reports on trapping and laser-cooling of singly-ionized strontium ions in a linear Paul trap. We demonstrate loading of large ion clouds containing as much as 106 ions and laser cooling down to the Coulomb crystal transition. We observe the spatial segregation of the different Sr+ isotopes due to the mass-dependent Paul trap stiffness. Sympathetic cooling of the different isotopes is demonstrated, either by laser-cooling of 88Sr+ (83% abundance) or of 86Sr+ (10% abundance). These demonstrations open the way to the use of a large ion Coulomb crystal for quantum optics and quantum information experiments, where the strong confinement, the long lifetime, and the absence of perturbation by cooling lasers are crucial.