The quantum electrodynamic (QED) description of light-and-matter interaction is one of the most f... more 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 [1–6]. 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 [7]. 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 [8]. Here we report on a novel measurement technique that overcomes both of these limitations by cotrapping two HCIs in a Penning trap and measuring the difference of their g facto...
Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016), 2017
The high-precision Penning-trap mass spectrometer PENTATRAP is currently being revised at the Max... more The high-precision Penning-trap mass spectrometer PENTATRAP is currently being revised at the Max-Planck-Institut für Kernphysik in Heidelberg. It uses five Penning traps with the goal to reach a relative uncertainty in mass-ratio determination below δm/m ≈ 10 −11. The first commissioning phase revealed the necessity to modify the cryogenic setup in order to increase the storage time for highly-charged ions. A pre-vacuum chamber will be implemented as well as a pumping barrier to separate the beamline vacuum from the high vacuum region of the traps.
The coupling of the motion of two ion species in separate Penning traps via a common tank circuit... more The coupling of the motion of two ion species in separate Penning traps via a common tank circuit is discussed. 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. An intermittent laser cooling method for sympathetic cooling is proposed and a theoretical description is provided. 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.
In Penning traps electromagnetic forces are used to confine charged particles under well-controll... more In Penning traps electromagnetic forces are used to confine charged particles under well-controlled conditions for virtually unlimited time. Sensitive detection methods have been developed to allow observation of single stored ions. Various cooling methods can be employed to reduce the energy of the trapped particle to nearly at rest. In this review we summarize how highly charged ions (HCIs) offer unique possibilities for precision measurements in Penning traps. Precision atomic and nuclear masses as well as magnetic moments of bound electrons allow among others to determine fundamental constants like the mass of the electron or to perform stringent tests of fundamental interactions like bound-state quantum electrodynamics. Recent results and future perspectives in high-precision Penning-trap spectroscopy with HCIs will be discussed.
State-of-the-art optical clocks [1] achieve fractional precisions of 10 −18 and below using ensem... more State-of-the-art optical clocks [1] achieve fractional precisions of 10 −18 and below using ensembles of atoms in optical lattices [2, 3] or individual ions in radiofrequency traps [4, 5]. They are used as frequency
We report on the successful demonstration of a novel scheme for detecting optical transitions in ... more We report on the successful demonstration of a novel scheme for detecting optical transitions in highly charged ions. We applied it to determine the frequency of the dipole-forbidden 2p 2 P 1=2 − 2 P 3=2 transition in the fine structure of 40 Ar 13þ using a single ion stored in the harmonic potential of a Penning trap. Our measurement scheme does not require detection of fluorescence, instead it makes use of the continuous Stern-Gerlach effect. Our value of 679.216464ð4Þ stat ð5Þ syst THz is in reasonable agreement with the current best literature values and improves its uncertainty by a factor of 24.
The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, tri... more The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, triton and helion, is of great importance for several fundamental tests in physics. However, the latest high-precision measurements of these masses carried out at different mass spectrometers indicate an inconsistency of five standard deviations. To determine the masses of the lightest ions with a relative precision of a few parts per trillion and investigate this mass problem a cryogenic multi-Penning trap setup, LIONTRAP (Light ION TRAP), was constructed. This allows an independent and more precise determination of the relevant atomic masses by measuring the cyclotron frequency of single trapped ions in comparison to that of a single carbon ion. In this paper the measurement concept and the first doubly compensated cylindrical electrode Penning trap, are presented. Moreover, the analysis of the first measurement campaigns of the proton's and oxygen's atomic mass is described in detail, resulting in mp = 1.007 276 466 598 (33) u and m 16 O = 15.994 914 619 37 (87) u. The results on these data sets have already been presented in [F. Heiße et al., Phys. Rev. Lett. 119, 033001 (2017)]. For the proton's atomic mass, the uncertainty was improved by a factor of three compared to the 2014 CODATA value. the Atomic Mass Evaluation (AME) [12, 13]. Unfortunately, especially the measurement of the interesting light ion (and particle) masses are complicated by the sizable systematic frequency shifts originating in the relatively large ratio of kinetic energies compared to the low rest mass energy. Consequently, we have developed the LIONTRAP (Light Ion TRAP) apparatus, which is optimized to minimize these systematic shifts. Recently, as a first application, we have performed a mea
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
An ultra-stable and low-noise 25-channel voltage source providing 0 to À 100 V has been developed... more An ultra-stable and low-noise 25-channel voltage source providing 0 to À 100 V has been developed. It will supply stable bias potentials for Penning-trap electrodes used in high-precision experiments. The voltage source generates all its supply voltages via a specially designed transformer. Each channel can be operated either in a precision mode or can be dynamically ramped. A reference module provides reference voltages for all the channels, each of which includes a low-noise amplifier to gain a factor of 10 in the output stage. A relative voltage stability of δ ≈ × − V V / 2 10 8 has been demonstrated at À 89 V within about 10 min.
The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=−g μBs ħ−1 with ... more The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=−g μBs ħ−1 with μB the Bohr magneton and s the electron’s spin, can be calculated by bound-state quantum electrodynamics (BS-QED) to very high precision. The recent ultra-precise experiment on hydrogen-like silicon determined this value to eleven significant digits, and thus allowed to rigorously probe the validity of BS-QED. Yet, the investigation of one of the most interesting contribution to the g-factor, the relativistic interaction between electron and nucleus, is limited by our knowledge of BS-QED effects. By comparing the g-factors of two isotopes, it is possible to cancel most of these contributions and sensitively probe nuclear effects. Here, we present calculations and experiments on the isotope dependence of the Zeeman effect in lithium-like calcium ions. The good agreement between the theoretical predicted recoil contribution and the high-precision g-factor measurements paves the way for a n...
Highly charged ions provide a unique opportunity to test our understanding of atomic properties u... more Highly charged ions provide a unique opportunity to test our understanding of atomic properties under extreme conditions: The electric field strength seen by an electron bound to a nucleus at the distance of the Bohr radius ranges from 1010 V/cm in hydrogen to1016 V/cm in hydrogenlike uranium. The theory of quantum electrodynamics (QED) allows for calculation e.g. of binding energies, transition probabilities or magnetic moments. While at low fields QED is tested to very high precision, new, hypothetical nonlinear effects like photon- photon interaction or a violation of Lorentz symmetry may occur in strong fields which then would lead to an extension of the Standard Model. The ultra-high precision determination of the magnetic moment of a bound electron in a highly charged ion provides a unique possibility to probe the validity of the current Standard Model in extreme conditions.
Penning-Fallen-Experiment mit bislang unerreichter Genauigkeit messen. Sie ist eine wichtige Mess... more Penning-Fallen-Experiment mit bislang unerreichter Genauigkeit messen. Sie ist eine wichtige Messgröße zur präziseren Bestimmung der Feinstrukturkonstante und von großer Bedeutung für die genauesten Tests der Quantenelektrodynamik.
Individual charged atomic or molecular particles can be confined by electromagnetic fields for ne... more Individual charged atomic or molecular particles can be confined by electromagnetic fields for nearly unlimited times under well controlled conditions in a small volume in space. This allows performing spectroscopic experiments with unprecedented accuracy. We discuss a project to determine the magnetic moment of the electron bound in hydrogen-like ions with different nuclear charges. This serves for testing bound-state quantum-electrodynamics calculations with high precision. Previous results on C 5+ and O 7+ as well as the present status of the project with Si 13+ and Ca 19+ are presented in this contribution and future possibilities are discussed.
A highly stable, low-noise voltage source was designed to improve the stability of the electrode ... more A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of ±15 and ±5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7×10−7 over 6.5 h and a noise level equal or smaller than 30 nV/Hz is achieved.
The quantum electrodynamic (QED) description of light-and-matter interaction is one of the most f... more 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 [1–6]. 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 [7]. 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 [8]. Here we report on a novel measurement technique that overcomes both of these limitations by cotrapping two HCIs in a Penning trap and measuring the difference of their g facto...
Proceedings of the 12th International Conference on Low Energy Antiproton Physics (LEAP2016), 2017
The high-precision Penning-trap mass spectrometer PENTATRAP is currently being revised at the Max... more The high-precision Penning-trap mass spectrometer PENTATRAP is currently being revised at the Max-Planck-Institut für Kernphysik in Heidelberg. It uses five Penning traps with the goal to reach a relative uncertainty in mass-ratio determination below δm/m ≈ 10 −11. The first commissioning phase revealed the necessity to modify the cryogenic setup in order to increase the storage time for highly-charged ions. A pre-vacuum chamber will be implemented as well as a pumping barrier to separate the beamline vacuum from the high vacuum region of the traps.
The coupling of the motion of two ion species in separate Penning traps via a common tank circuit... more The coupling of the motion of two ion species in separate Penning traps via a common tank circuit is discussed. 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. An intermittent laser cooling method for sympathetic cooling is proposed and a theoretical description is provided. 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.
In Penning traps electromagnetic forces are used to confine charged particles under well-controll... more In Penning traps electromagnetic forces are used to confine charged particles under well-controlled conditions for virtually unlimited time. Sensitive detection methods have been developed to allow observation of single stored ions. Various cooling methods can be employed to reduce the energy of the trapped particle to nearly at rest. In this review we summarize how highly charged ions (HCIs) offer unique possibilities for precision measurements in Penning traps. Precision atomic and nuclear masses as well as magnetic moments of bound electrons allow among others to determine fundamental constants like the mass of the electron or to perform stringent tests of fundamental interactions like bound-state quantum electrodynamics. Recent results and future perspectives in high-precision Penning-trap spectroscopy with HCIs will be discussed.
State-of-the-art optical clocks [1] achieve fractional precisions of 10 −18 and below using ensem... more State-of-the-art optical clocks [1] achieve fractional precisions of 10 −18 and below using ensembles of atoms in optical lattices [2, 3] or individual ions in radiofrequency traps [4, 5]. They are used as frequency
We report on the successful demonstration of a novel scheme for detecting optical transitions in ... more We report on the successful demonstration of a novel scheme for detecting optical transitions in highly charged ions. We applied it to determine the frequency of the dipole-forbidden 2p 2 P 1=2 − 2 P 3=2 transition in the fine structure of 40 Ar 13þ using a single ion stored in the harmonic potential of a Penning trap. Our measurement scheme does not require detection of fluorescence, instead it makes use of the continuous Stern-Gerlach effect. Our value of 679.216464ð4Þ stat ð5Þ syst THz is in reasonable agreement with the current best literature values and improves its uncertainty by a factor of 24.
The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, tri... more The precise knowledge of the atomic masses of light atomic nuclei, e.g. the proton, deuteron, triton and helion, is of great importance for several fundamental tests in physics. However, the latest high-precision measurements of these masses carried out at different mass spectrometers indicate an inconsistency of five standard deviations. To determine the masses of the lightest ions with a relative precision of a few parts per trillion and investigate this mass problem a cryogenic multi-Penning trap setup, LIONTRAP (Light ION TRAP), was constructed. This allows an independent and more precise determination of the relevant atomic masses by measuring the cyclotron frequency of single trapped ions in comparison to that of a single carbon ion. In this paper the measurement concept and the first doubly compensated cylindrical electrode Penning trap, are presented. Moreover, the analysis of the first measurement campaigns of the proton's and oxygen's atomic mass is described in detail, resulting in mp = 1.007 276 466 598 (33) u and m 16 O = 15.994 914 619 37 (87) u. The results on these data sets have already been presented in [F. Heiße et al., Phys. Rev. Lett. 119, 033001 (2017)]. For the proton's atomic mass, the uncertainty was improved by a factor of three compared to the 2014 CODATA value. the Atomic Mass Evaluation (AME) [12, 13]. Unfortunately, especially the measurement of the interesting light ion (and particle) masses are complicated by the sizable systematic frequency shifts originating in the relatively large ratio of kinetic energies compared to the low rest mass energy. Consequently, we have developed the LIONTRAP (Light Ion TRAP) apparatus, which is optimized to minimize these systematic shifts. Recently, as a first application, we have performed a mea
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
An ultra-stable and low-noise 25-channel voltage source providing 0 to À 100 V has been developed... more An ultra-stable and low-noise 25-channel voltage source providing 0 to À 100 V has been developed. It will supply stable bias potentials for Penning-trap electrodes used in high-precision experiments. The voltage source generates all its supply voltages via a specially designed transformer. Each channel can be operated either in a precision mode or can be dynamically ramped. A reference module provides reference voltages for all the channels, each of which includes a low-noise amplifier to gain a factor of 10 in the output stage. A relative voltage stability of δ ≈ × − V V / 2 10 8 has been demonstrated at À 89 V within about 10 min.
The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=−g μBs ħ−1 with ... more The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=−g μBs ħ−1 with μB the Bohr magneton and s the electron’s spin, can be calculated by bound-state quantum electrodynamics (BS-QED) to very high precision. The recent ultra-precise experiment on hydrogen-like silicon determined this value to eleven significant digits, and thus allowed to rigorously probe the validity of BS-QED. Yet, the investigation of one of the most interesting contribution to the g-factor, the relativistic interaction between electron and nucleus, is limited by our knowledge of BS-QED effects. By comparing the g-factors of two isotopes, it is possible to cancel most of these contributions and sensitively probe nuclear effects. Here, we present calculations and experiments on the isotope dependence of the Zeeman effect in lithium-like calcium ions. The good agreement between the theoretical predicted recoil contribution and the high-precision g-factor measurements paves the way for a n...
Highly charged ions provide a unique opportunity to test our understanding of atomic properties u... more Highly charged ions provide a unique opportunity to test our understanding of atomic properties under extreme conditions: The electric field strength seen by an electron bound to a nucleus at the distance of the Bohr radius ranges from 1010 V/cm in hydrogen to1016 V/cm in hydrogenlike uranium. The theory of quantum electrodynamics (QED) allows for calculation e.g. of binding energies, transition probabilities or magnetic moments. While at low fields QED is tested to very high precision, new, hypothetical nonlinear effects like photon- photon interaction or a violation of Lorentz symmetry may occur in strong fields which then would lead to an extension of the Standard Model. The ultra-high precision determination of the magnetic moment of a bound electron in a highly charged ion provides a unique possibility to probe the validity of the current Standard Model in extreme conditions.
Penning-Fallen-Experiment mit bislang unerreichter Genauigkeit messen. Sie ist eine wichtige Mess... more Penning-Fallen-Experiment mit bislang unerreichter Genauigkeit messen. Sie ist eine wichtige Messgröße zur präziseren Bestimmung der Feinstrukturkonstante und von großer Bedeutung für die genauesten Tests der Quantenelektrodynamik.
Individual charged atomic or molecular particles can be confined by electromagnetic fields for ne... more Individual charged atomic or molecular particles can be confined by electromagnetic fields for nearly unlimited times under well controlled conditions in a small volume in space. This allows performing spectroscopic experiments with unprecedented accuracy. We discuss a project to determine the magnetic moment of the electron bound in hydrogen-like ions with different nuclear charges. This serves for testing bound-state quantum-electrodynamics calculations with high precision. Previous results on C 5+ and O 7+ as well as the present status of the project with Si 13+ and Ca 19+ are presented in this contribution and future possibilities are discussed.
A highly stable, low-noise voltage source was designed to improve the stability of the electrode ... more A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of ±15 and ±5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7×10−7 over 6.5 h and a noise level equal or smaller than 30 nV/Hz is achieved.
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Papers by Sven Sturm