arXiv subjects

Bingsheng Tu

Publications and source records attributed to Bingsheng Tu.

10 recordsLinked to original sources

arXiv2026

Development of a High-Performance Permanent Magnet System for Ion Trapping Experiments

This work presents the design and fabrication of a compact permanent magnet based on an optimized stacked structure of fifteen NdFeB rings. The tunable NS-SN-NS configuration generates a central magnetic field of 0.8T with a reconstructed uniformity of 99.988% within a 1mm radius spherical volume. The remaining field inhomogeneity is dominated by radial dipole components. Requiring neither cryogenics nor external power, this design provides a high-performance and cost-effective alternative to superconducting magnets for applications in ion-trap development and Fourier-transform ion cyclotron resonance mass spectrometry.

physics.atom-ph↗

arXiv2026

Development of a compact cryogenic Penning trap with permanent magnets: An intermediate step toward the Shanghai Penning Trap

Penning traps, renowned for their unparalleled precision in determining fundamental properties such as mass and magnetic moments, are cornerstone instruments in modern physics. Their applications span from nuclear structure studies to stringent tests of quantum electrodynamics and CPT invariance. Although Penning traps have been demonstrated for fundamental studies, often employing superconducting magnets, their high cost and operational complexity remain challenges. In this work, we report the development of a compact cryogenic Penning trap that utilizes a permanent magnet to provide a confining magnetic field, offering a more economical and flexible alternative. We have successfully demonstrated all core functionalities of this system, including ion generation, transport, confinement, manipulation, and signal detection. This compact trap not only serves as a vital technical testbed for the development of the Shanghai Penning Trap, but also establishes a cryogenic Penning-trap experiment platform for ion trapping and cooling applications as well as envisaged spectroscopic studies applications.

physics.atom-ph↗

arXiv2026

High-precision Penning-trap spectroscopy of the ground-state spin structure of HD+

We present high-precision spectroscopy of the ground-state hyperfine structure of HD$^+$ at 4~T. We determine the bound-electron $g$ factor, $g_{e,\mathrm{bound}} = -2.002\,278\,540\,96(40)$, to a relative uncertainty of $2\times$10$^{-10}$, the most precise determination of a bound-electron $g$ factor of a molecular ion to date. The experimental value agrees with recently developed ab initio theory that now includes quantum-electrodynamical effects up to order $α^5$ and has reduced the theoretical uncertainty by three orders of magnitude [O. Kullie \textit{et al.}, Phys. Rev. A 112 052813 (2025)]. In addition, we extract the scalar spin-spin interaction coefficients $E_4$~=~925\,395.758(41)$\,$kHz (electron-proton) and $E_5$~=~142\,287.821(22)$\,$kHz (electron-deuteron), which show a moderate tension with another state-of-the-art theoretical prediction [M. Haidar \textit{et al.}, Phys. Rev. A 106 042815 (2022)].

physics.atom-ph↗

arXiv2026

New energy conversion system based on charge-exchange and inner-shell electron transitions

The rapidly growing demand for compact, high-energy power sources has outpaced the capabilities of conventional electrochemical systems that rely on outer-shell redox reactions. In this work, we present a new energy platform that utilizes inner-shell electron transitions that are previously inaccessible due to their high energy thresholds. By leveraging charge exchange processes between bare argon ions (Ar^18+) and neutral helium atoms, we provide clear evidence for the emission of soft X-ray and extreme-ultraviolet photons across a broad spectra range, resulting from inner-shell electron capture and cascade de-excitation. This strategy overcomes the limitations of radiative recombination by enhancing photon energy utilization through broader emission profiles more compatible with practical energy converters. Our design of a helium-filled chamber design enables precise control of output via pressure tuning, achieving a remarkable radiation power density of 6.29*10^8 W L^-1 and an unprecedented energy density of 2.64*10^6 Wh kg^-1. These results may provide a new and effective paradigm for energy conversion systems with ultra-high power and energy densities based on inner-shell electrons.

physics.atom-ph↗

arXiv2025

Testing inter-electronic interaction in lithium-like tin

Magnetic moments of bound-electron systems are a sensitive tool for testing fundamental interactions. $g$ factors of lithium-like ions have been rigorously studied in recent years, enabling insights into the relativistic inter-electronic effects. Here, we present the $g$-factor measurement of lithium-like tin, accurate to 0.5 parts per billion, as well as \textit{ab initio} theoretical calculations that include an advanced treatment of the inter-electronic interaction. We further improve the prediction by using the experimental result for the hydrogen-like tin $g$ factor, inferring from it the unknown higher-order QED effects. The observed agreement independently confirms the revised theory at a previously inaccessible high nuclear charge $Z$ of 50, where QED effects are significantly larger.

physics.atom-ph↗

arXiv2025

Prediction of Nuclear Clock Transitions Frequency Difference between $^{229}$Th$^{3+}$ and $^{229}$Th$^{4+}$ via \textit{ab-initio} Self-Consistent Field Theory

The $^{229}\text{Th}$ isotope is a promising candidate for nuclear clocks, with its transition frequency influenced by electron-induced nuclear frequency shifts. This effect is comparatively small and requires high-precision theoretical calculations. In this work, we employed a non-perturbative multi-configuration Dirac-Hartree-Fock (MCDHF) method, in contrast to the perturbation theory used previously, to resolve the field shift effect. This method accounts for subtle differences in the nuclear potential while considering the $^{229}\text{Th}$ isotope in both its ground and isomeric states. Consequently, the nuclear transition frequency difference of between $^{229}\text{Th}^{3+}$ and $^{229}\text{Th}^{4+}$ was determined to be $-639$~MHz with computational convergency down to 1~MHz. Given recent precision measured transition frequency of $^{229}\text{Th}^{4+}$in $^{229}\text{Th}$-doped CaF$_2$ [Nature 633, 63 (2024)], the transition frequency of isolated $^{229}\text{Th}^{3+}$ is predicted to be $2,020,406,745 (1)_\text{comp.}(77)_{δ\langle r^2 \rangle} (100)_\text{ext.}$~MHz, with brackets indicating uncertainties stemming from our atomic structure computations, the input nuclear charge radii from nuclear data tables, and the influence of the crystal environment as reported in the literature. This provides valuable guidance for direct laser excitation of isolated $^{229}\text{Th}^{3+}$ based on ion traps experiments.

physics.atom-ph↗

arXiv2025

Probing Nuclear Excitation by Electron Capture in an Electron Beam Ion Trap with Non-destructive Isomer Detection via Precision Mass Spectrometry

Nuclear excitation by electron capture (NEEC) is an important nuclear excitation mechanism which still lacks conclusive experimental verification. This is primarily attributed to strong background x-/$γ$-ray noise and competing nuclear excitation processes which would overshadow the signals in various environments that NEEC takes place. Here, we propose an experimental approach to observe the NEEC process within a background-free environment. Through collisions with a highly-compressed mono-energetic electron beam in an electron beam ion trap, nuclei may get excited to a long-lived isomeric state via the NEEC process. Subsequently, ions can be extracted and Penning-trap mass spectrometry employed to unambiguously detect the isomer. Our study focuses on the promising candidate $^{189}\mathrm{Os}$, demonstrating measurable detection rates of the NEEC process and discussing the feasibility of the proposed approach. This new approach for observing the NEEC process may be realized in the near future.

nucl-ex↗

arXiv2023

Experimental Access to Observing Decay from Extremely Long-Lived Metastable Electronic States via Penning Trap Spectrometry

Long-lived ionic quantum states known as metastable electronic states in highly-charged ions (HCIs) are of great interest in fundamental physics. Especially, it generates transitions with very narrow natural linewidth which is a promising candidate for use in the next generation HCI atomic clocks to reach an accuracy below $10^{-19}$. A recent experiment reported in [Nature,581(7806) 2020], used Penning trap mass spectrometry to measure the energy of an extremely long-lived metastable electronic state, thus opening doors to search for HCI clock transitions. Building upon prior research, this study introduces an experimental proposal with the goal of measuring lifetimes of the metastable states beyond seconds. Our approach employs a sequential pulse-and-phase measurement scheme, allowing for direct observations of the decay processes from metastable electronic states through single-ion mass spectrometry in a Penning trap. This measurement poses a significant challenge to conventional techniques like fluorescence detection. To demonstrate the effectiveness of this method, we conducted a comprehensive simulation under real experimental conditions, yielding promising results in a specific scenario. Two suitable candidates are proposed for testing this method, and the state-of-the-art MCDHF theory are employed for accurate energy levels and transition rate calculations. Some future prospects in the experimental determinations of a wide range of energy and lifetimes of long-lived metastable electronic states, probing hyperfine and magnetic quenching effects on high-order forbidden transitions and search for highly quality HCI clock transitions are discussed.

physics.atom-ph↗

arXiv2022

Direct Bound-Electron $g$ factor Difference Measurement with Coupled Ions

The quantum electrodynamic (QED) description of light-and-matter interaction is one of the most fundamental theories of physics and has been shown to be in excellent agreement with experimental results. Specifically, measurements of the electronic magnetic moment (or $g$ factor) of highly charged ions (HCI) in Penning traps can provide a stringent probe for QED, testing the Standard model in the strongest electromagnetic fields. When studying the difference of isotopes, even the intricate effects stemming from the nucleus can be resolved and tested as, due to the identical electron configuration, many common QED contributions do not have to be considered. Experimentally however, this becomes quickly limited, particularly by the precision of the ion masses or the achievable magnetic field stability. Here we report on a novel measurement technique that overcomes both of these limitations by co-trapping two HCIs in a Penning trap and measuring the difference of their $g$ factors directly. The resulting correlation of magnetic field fluctuations leads to drastically higher precision. We use a dual Ramsey-type measurement scheme with the ions locked on a common magnetron orbit, separated by only a few hundred micrometres, to extract the coherent spin precession frequency difference. We have measured the isotopic shift of the bound electron $g$ factor of the neon isotopes of $^{20}$Ne$^{9+}$ and $^{22}$Ne$^{9+}$ to 0.56 parts-per-trillion ($5.6 \cdot 10^{-13}$) precision relative to their $g$ factors, which is an improvement of more than two orders of magnitude compared to state-of-the-art techniques. This resolves the QED contribution to the nuclear recoil for the very first time and accurately validates the corresponding theory. Furthermore, the agreement with theory allows setting constraints for a fifth-force, resulting from Higgs-portal-type dark-matter interactions.

physics.atom-ph↗

arXiv2021

Tank-Circuit Assisted Coupling Method for Sympathetic Laser Cooling

We discuss the coupling of the motion of two ion species in separate Penning traps via a common tank circuit. The enhancement of the coupling assisted by the tank circuit is demonstrated by an avoided crossing behavior measurement of the motional modes of two coupled ions. We propose an intermittent laser cooling method for sympathetic cooling and provide a theoretical description. The technique enables tuning of the coupling strength between two ion species in separate traps and thus allows for efficient sympathetic cooling of an arbitrary type of single ion for high-precision Penning-trap experiments.

quant-ph↗