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April 2014 - present
April 2011 - April 2014
April 2008 - April 2011
Publications
Publications (246)
We have studied the cooling dynamics, formation process and geometric structure of mesoscopic crystals of externally produced magnesium ions in a Penning trap. We present a cooling model and measurements for a combination of buffer gas cooling and laser cooling which has been found to reduce the ion kinetic energy by eight orders of magnitude from...
We present measurements of resistive and sympathetic cooling of ion clouds
confined in a Penning trap. For resistive cooling of a cloud consisting of one
ion species, we observe a significant deviation from exponential cooling
behavior which is explained by an energy-transfer model. The observed
sympathetic cooling of simultaneously confined ion sp...
Highly charged ions represent environments that allow to study precisely one or more bound electrons subjected to unsurpassed electromagnetic fields. Under such conditions, the magnetic moment (g-factor) of a bound electron changes significantly, to a large extent due to contributions from quantum electrodynamics. We present three Penning-trap expe...
The value of the electron's magnetic moment is a fundamental quantity in physics. Its deviation from the value expected from Dirac theory has given enormous impetus to the field of quantum theory and especially to quantum electrodynamics (QED) as the relativistic quantum field theory of electrodynamics. In fact, the measured values both for free an...
We present a non-destructive electronic detector for stored charged particles in a Penning trap that uses a symmetric electrode arrangement for signal pickup and a resonator without tap. This system has advantageous off-resonance features which are demonstrated by means of detection and cooling measurements with highly charged ions in a cryogenic P...
We present a systematic and quantitative investigation of the electrostatic anharmonicity in cylindrical Penning traps that is induced by the presence of radial holes for access to the trap center. The expected distortion of the electrostatic potential is studied as a function of the relative hole size, shape, arrangement, and number.
Penning traps have established themselves as premier tools for high-precision spectroscopy in the radio-frequency, optical and microwave domains. They facilitate mass measurements of elements and their isotopes, measurements of magnetic moments of the electron/positron, of the proton/anti-proton and of the bound electron. In that, they yield access...
In the previous chapter, we have discussed the effects of field imperfections on the motion of a single confined particle in a Penning trap. These effects can in principle be avoided, and can in reality be minimised by careful choice of parameters and of the trap manufacturing details. Here, we will discuss effects that are inherent to the confinem...
This chapter gives a brief description of what a Penning trap is, a short account of the history of Penning traps (for more details see appendix), and presents the central characters involved in its development, together with a coarse overview of the main fields of operation of such traps and their relation to other storage devices for charged part...
In contrast to the situation with a single particle in a trap, the presence of many charged particles gives rise to long-range particle-particle interactions, collective effects, and partial shielding of the trap potential that leads to shifts of the oscillation frequencies. Here, we briefly discuss the most important collective effects and review...
The possibility to cool the motions of confined particles is one key motivation for the use of Penning traps, particularly for precision spectroscopy in any frequency domain. Here, we discuss the notion of particle temperature and its measurement in different experimental situations, before we review the most important cooling techniques applied in...
In this chapter we look at cooling techniques that are neither electronic nor optical by nature, this refers to sympathetic cooling, buffer gas cooling and evaporative cooling.
Particle oscillations in different motional degrees of freedom in the Penning trap can purposefully be resonantly coupled by suitable electromagnetic radiation. Here, we briefly discuss the phenomenology and the main applications.
This chapter briefly reviews the measurements of magnetic moments that have been performed by application of the continuous Stern-Gerlach effect to a single particle confined in a Penning trap with a magnetic bottle.
This chapter takes a look at the effects and possible implementations of specific magnetic field geometries, mainly of so-called ‘magnetic bottles’ which are a key ingredient to the application of the continuous Stern-Gerlach effect in Penning traps.
This chapter takes a short look at mass spectrometry in Penning traps, which to some extent is one specific application of radio-frequency spectroscopy of the particle oscillations in the trap. We have a brief look at precision mass spectrometry, and then discuss mass spectrometry as an analytical tool for a quantitative determination of the trap c...
Confined particles can be excited non-resonantly, or resonantly by suited electromagnetic radiation at the frequency of the respective motion. This refers to individual axial and radial oscillation frequencies of single particles or particle ensembles, excitation of sidebands for motional coupling, and also to collective frequencies of ensembles su...
This chapter is concerned with the motion that is performed by a single confined test particle in a Penning trap. For now we disregard any realisation of a Penning trap and see it as the abstract combination of an ideally homogeneous static magnetic field \(B_0\) perfectly aligned with a quadrupolar electrostatic potential \(\bar{U}\) that creates...
The oldest Penning trap geometry in use is the hyperbolic shape, which provides good confinement properties by design, however was difficult to machine to high precisions at the time of its introduction, and offers limited access for particles and laser beams. Thus, cylindrical designs were brought forward, including more open structures with open...
In this chapter we look at laser cooling of confined particles in a Penning trap. Some of these methods are very involved, depend on the details of the particles rather than on the confinement situation, and hence we will only briefly review them.
Deviations from the idealised situation described in Chap. 6 as they are present in real Penning traps give rise to a number of effects. Some of these can be minimized by efforts to approach the ideal situation as closely as possible. Others are inherent to the situation and cannot be avoided or circumvented, and we will discuss them below. In part...
In this chapter, we briefly have a look at a number of variations on the idea of a Penning trap, i.e. at specific deviations from the combination of a homogeneous magnetostatic field with an aligned quadrupolar electrostatic potential. We discuss only those designs that use magnetic and electric fields, i.e. we are not concerned with Paul traps, Ki...
In this chapter, we have a look at the way in which the concept can be implemented. It shows the capabilities of the most common Penning trap implementations, compares the confinement situation in Penning traps to those of other types such as optical and acoustic traps, and shows the most important features of experimental implementations of Pennin...
In this chapter, we take a look at the non-destructive detection of confined particles and the measurement of their oscillation frequencies by use of resonant electronic circuits. This includes superconducting circuits and their properties in the external magnetic field of the Penning trap.
In this chapter we look at the most common electronic techniques applied to cool the motions of confined particles in a Penning trap, foremost at resistive cooling, but also at other techniques that make use of the electronic systems of a Penning trap.
In this chapter, we have a look at the underlying working principle of the Penning trap, discuss the notion of particle confinement, the main properties of the confined state, and illustrate the spatial configuration of the confining fields.
In special situations, optical and microwave spectroscopy can be combined to constitute a powerful tool that uses the high spectral resolution of the microwaves and the good detection properties of optical light. Here, we briefly discuss its application to the determination of magnetic moments of the nucleus and the electron bound in highly charged...
We have performed systematic measurements of the resistive cooling behavior of bunches of highly charged ions in a Penning trap after injection from an external source. In particular, we have been able to measure the exponential cooling rate of the axial center-of-mass motion and experimentally show its linear dependence on the ion number within th...
We have developed and operated an electronic detection system for the non-destructive single-pass detection of bunches of charged particles in a beamline that allows for a measurement of their lateral position with respect to the central beamline axis on a shot-to-shot basis. It provides all features of our related development reported in Kiffer et...
We have conceived, built, and operated a cryogenic vacuum valve with opening and closing times as short as 50 ms that can be used in strong magnetic fields and across a broad range of duty cycles. It is used to seal a cryogenic Penning trap at liquid-helium temperature for long-term storage of highly charged ions in a vacuum better than 10−15 hPa f...
We have built and operated a cryogenic Penning trap arrangement
that allows for the efficient production, selection, and long-term storage of highly
charged atomic ions. In close similarity to an electron-beam ion trap (EBIT)
it works by electron-impact ionisation of atoms inside a dedicated confinement
region. The electrons are produced by field e...
We have conceived and built the HILITE (High-Intensity Laser-Ion Trap Experiment) Penning-trap setup for the production, confinement and preparation of pure ensembles of highly charged ions in a defined quantum state as a target for various high-intensity lasers. This enables a broad suite of laser-ion interaction studies at high photon energies an...
Synopsis
We present non-destructive single-pass ion bunch detection and characterisation by measuring the induced image charge in a detection electrode. The presented technique allows direct determination of ion kinetic energy, absolute ion number and spatial ion bunch length. We will show the results of corresponding measurements with bunches of l...
Synopsis
We present a Penning-trap-based setup for the study of light-matter interactions in the high-power and/or high-intensity laser regime, such as multi-photon ionization and field ionization. The setup applies ion-cloud formation techniques to highly charged ions to the end of specific target preparation, as well as non-destructive detection...
We have devised an experimental method and apparatus for the simultaneous nondestructive determination of the absolute ion number, ion kinetic energy, and length of bunches of charged particles. We have built and operated a corresponding electronic detector that is based on induced charges and their subsequent low-noise amplification at cryogenic t...
We describe the results of analytical calculations and numerical simulations of the confinement properties of a mechanically compensated cylindrical Penning trap which has conical endcap openings for large-solid-angle access for example with highly focused laser beams. While the analytical calculations show that under the common geometrical conditi...
Detailed investigations of laser–ion interactions require well‐defined ion targets and detection techniques for high‐sensitivity measurements of reaction educts and products. To this end, we have designed and built the High‐Intensity Laser‐Ion Trap Experiment Penning trap setup, which features various ion‐target preparation techniques including sel...
The hyperfine splitting in heavy highly charged ions provide the means to test QED in extremely strong magnetic fields. In order to provide a meaningful test, the splitting has to be measured in H-like and Li-like ions to remove uncertainties from nuclear structure. This has been achieved at the experimental storage ring ESR but a discrepancy to th...
We perform a detailed experimental study of resistive cooling of large ensembles of highly charged ions such as Ar13+ in a cryogenic Penning trap. Different from the measurements reported by Vogel et al. [M. Vogel et al., Phys. Rev. A 90, 043412 (2014)], we observe purely exponential cooling behavior when conditions are chosen to allow collisional...
Penning traps have established themselves as premier tools for high-precision spectroscopy in the radio frequency, optical and microwave domains. They facilitate mass measurements of elements and their isotopes, measurements of magnetic moments of the electron / positron, of the proton / antiproton and of the bound electron. In that, they yield acc...
We have conceived, built, and operated a cryogenic Penning trap with an electrically conducting yet optically transparent solid electrode. The trap, dedicated to spectroscopy and imaging of confined particles under large solid angles, is of “half-open” design with one open endcap and one closed endcap that mainly consists of a glass window coated w...
We have studied the formation and properties of two-species ion Coulomb crystals in the Penning trap of the SpecTrap experiment. These crystals have been formed by injection of admixture ions from an external source into a previously confined and laser-cooled cloud of magnesium ions. This kind of study, performed over a range of the admixture ions’...
World Scientific, Singapore advanced undergraduate students and above Manuel Vogel, GSI Darmstadt, m.vogel@gsi.de This is the first volume of the new 'Peking University-World Scientific Advance Physics Series', which is a collaborative effort of the Peking University Press with the World Scientific Publishing Company. It is the intention of this se...
We have measured the characteristics of a superconducting radio-frequency resonator in an external magnetic field. The magnetic field strength has been varied with 10 mT resolution between zero and 6 T. The resonance frequency and the quality factor of the resonator have been found to change significantly as a function of the magnetic field strengt...
We have built, operated, and characterized a compact ion source for low-energy bunches of singly charged atomic ions in a vacuum beam line. It is based on atomic evaporation from an electrically heated oven and ionization by electron impact from a heated filament inside a grid-based ionization volume. An adjacent electrode arrangement is used for i...