HITRAP Facility and Experiments - Status and Future Perspectives

Deceleration of highly charged ions is a mode for the operation for the ESR storage ring at GSI which is required for various types of experiments. The special requirement for HITRAP is the deceleration down to an energy of 4 MeV/u precisely, which is close to the minimum design value, in combination with fast extraction. The deceleration can start from any injection energy, but for efficient...

HITRAP Decelerator Status

The HITRAP decelerator facility aims to decelerate and cool heavy, highly-charged ions (HCI) like U$^{92+}$ [1]. After creation of the high charge states at relativistic energies, HITRAP decelerates these ions via a consecutive arrangement of linear deceleration stages and a cylindrical Penning trap. Within this so-called cooling trap, the ions can be cooled to low temperatures before they are...

The HITRAP facility is designed to decelerate and cool a bunch of about 10$^5$ heavy, highly charged ions (HCI). Produced by stripping at high energy, the HCI are decelerated eventually in a linear decelerator down to 6$\,$keV/u and captured within a cylindrical Penning trap. In that trap the HCI can be cooled using electron cooling before being transferred to subsequent experiments [1]. If...

The demand for beamtime at GSI infrastructures like ESR, CRYRING or HITRAP has increased over the last years and cannot be fully covered by the GSI accelerator infrastructure. Local ion sources play an important role to close this gap and allow for ‘offline operation’ of experiments at GSI [1].
Electron Beam Ion Traps (EBITs) are widely known as a versatile tool for spectroscopic studies of...

Slow highly charged ions deposit large amounts of their potential energy within the very first monolayers of a material. Depending on material properties, relaxation processes can also lead to permanent nanosized material modifications, e.g. hillocks and craters on surfaces of bulk samples - often in a similar manner as after swift heavy ion impact.
The type of created defect might vary even...

See Attachment (Abstract in better format)

In the past two decades it has become possible to isolate monolayers of bulk materials.
These new types of target materials are effectively 2-dimensional (2D) and as such have
opened up new possibilities for material research. In particular, we are interested in the
response of these targets to strong fields when irradiated with highly...

Slow single charged ions interacting with solid surfaces dissipate their kinetic energy mainly by nuclear collisions which results in, e.g. defect creation and erosion of material from the surface. Highly charged ions (HCI) are missing a few or even all of their electrons, and therefore carry additional potential energy, which is defined as the sum of the binding energies of all the electrons...

Investigations of the interaction of highly charged ions (HCI) with solid surfaces started back almost 20 years ago at the HZDR Ion Beam Center (IBC). In particular, first experiments focused on the determination of channels for potential energy dissipation in solids [1].

Successively, systematic studies on HCI induced modifications of surface topography on the nm scale were conducted...

Charge exchange (CX), the atomic process in which a bound electron from a neutral atom or molecule is tranferred into a highly excited state of a highly charged ion (HCI), results in the emission of a complex characteristic x-ray spectrum. Relative line intensities in this spectrum depend on the donor and acceptor species, as well as their relative velocity.

CX contributes to spectra of...

GSI has an active program of laser spectroscopy experiments with highly charged heavy ions. The focus of the measurements is on the study of fundamental interactions in extreme electric and magnetic fields, like they are available in few electron configurations of these heavy ions. The applied experimental methods comprise on the one hand laser spectroscopy of relativistic ions in storage...

With its roots in collision physics, back in the late 1980, COLTRIMS-setups (COLd Target Recoil Ion Momentum Spectroscopy) or Reaction microscopes, as they are also termed, are widely used in modern AMO-physics. Technically they consist of a super sonic gas jet, the imaging spectrometer and position and time-sensitive detectors. The super sonic gas jet provides the target, covering basically...

Please see the attached .doc file.

The ultra-intense X-ray pulses produced by novel free-electron lasers promise
many applications, e.g. for protein structure-determination or time-resolved
molecular spectroscopy. This requires the pulses to be well-characterised in
terms of focal shape, duration and intensity. Providing tools for calibrating
these properties is however a difficult task, leading to various approaches...

We implement a liquid metal ion source\,(LMIS) in a 3D coincidence momentum spectroscopy setup for studying the interaction of ionic targets with intense laser pulses. Laser intensities of up to 4$\cdot$10$^{16}$\,W/cm$^2$ allow for the observation of up to 10-fold ionization of Au$^+$-ions and double ionization of Si$^{2+}$-ions. Further, by utilizing two-color sculpted laser fields to...

The influence of relativistic effects on tunnel ionisation of electronic systems was described in detail by theory. For hydrogen-like ions of atomic charge $Z$ and laser radiation intensity $I$ these effects become significant for $Z > 45 (I/I_0)^{0.1}$, with $I_0=10^{22}\,$W/cm$^2$. This motivates the use of highly-charged ions to investigate ionisation. Suitable candidates are hydrogen-like...

At present, there are several methods for relativistic calculations of atomic structure and properties, such as multiconfiguration Dirac-Fock, coupled cluster, configuration interaction (CI), many-body perturbation theory (MBPT), their combination, and others. Generally, these approaches can provide accurate and reliable results for atoms and ions with a small number of valence electrons....

An ab initio QED approach to treat a valence-hole excitation in closed shell systems is developed in the framework of the two-time-Green function method. The derivation considers a redefinition of the vacuum state and its excitation as a valence-hole pair. The proper two-time Green function, whose spectral representation confirms the poles at valence-hole excitation energies is proposed. An...

The high-precision measurement of the Zeeman splitting of fine and hyper fine-structure levels can be measured using spectroscopy techniques. The Penning trap ARTEMIS at the HITRAP facility at GSI utilises such a method called Laser-Microwave double-resonance spectroscopy to measure the magnetic moment and to test bound-state QED calculations by the g-factor measurements of heavy,...

ARTEMIS (AsymmetRic Trap for measurement of Electron Magnetic moment in IonS) is a Penning trap-based experiment at HITRAP in GSI, Darmstadt, which is aiming to measure the g-factor of heavy, highly charged ions (such as U91+) as one of the most stringent tests of quantum electrodynamics. These ions in the magnetic and electric fields of the Penning trap demonstrate a distinctive motion that...

The studies on creation of surface nanostructures on metals, semiconductors and insulators are important for development of new technologies for production of microelectronic devices [1]. Structures of nanometric sizes can be created, for example, in collisions of highly charged ions (HCI) with surfaces of various materials. In this case different parameters of the ion beams, irradiated...

The M-X-rays emitted from Rydberg (n~30) hollow atoms (RHA) created in collisions of highly charged Xe$^{q+}$ ions (q=23-36) with Be surface were measured and interpreted in terms of the MCDF calculations [1] as a cascade of nf-3d electric dipole X-ray transitions, including their M-shell hypersatellites. The measured X-ray spectra indicate the importance of two-electron processes, in...

The theoretical uncertainty of the bound-electron $g$-factor in heavy hydrogen-like ions is dominated by uncalculated QED Feynman diagrams with two self-energy loops. Precision calculations of these diagrams in which the interaction between electron and nucleus is treated exactly are needed to improve the theoretical accuracy of the bound-electron $g$-factor in the high-$Z$ regime. Results of...

In electron-electron interactions in electromagnetic systems, retardation in the exchange of a virtual photon is essentially important as the first-order quantum electrodynamics correction. However, the retardation effect is generally so small that it is buried in unretarded electric and magnetic interactions and thus has yet to be directly probed. Here, we present a giant contribution of the...

While the study of the dynamics in scattering reactions between ions and atoms or molecules is a research field with a very long tradition, there are still many interesting and new aspects that are presently investigated. As compared to other projectile species such as electrons or photons, ions are particularly attractive because the allow to generate the shortest (down to zeptoseconds) and...

Helium-like ions are the simplest atomic multibody systems and their study along the isoelectronic sequence provides a unique testing ground for the interplay of the effects of electron–electron correlation, relativity and quantum electrodynamics. However, for high-Z ions with nuclear charge Z > 54, where inner-shell transition energies reach up to 100 keV, there is currently no data available...

When coming close to an atom, a muon can be captured by the nucleus and form a hydrogen-like
muonic ion, which is typically also surrounded by atomic electrons. This atomic system is commonly
referred to as a muonic atom. Due to the muon’s high mass, it is located much closer to the nucleus;
and, especially for heavy nuclei, this results in big nuclear size effects and a strong dependence...

The accuracy of quantum electrodynamics tests in strong fields has been tested up to now by measuring transition energies in highly-charged ions, using accelerator facilities and ion sources (see, e.g., [1] and Refs. there in). New applications like atomic mass measurements with 10-11 relative accuracy, performed using advanced ion traps, require the evaluation of total binding energy...

We present a fully open source hardware solution for the next generation of diode lasers for highly charged ion experiments. Our solution, consisting of a laser driver, a temperature controller and a fast servo, provides superior performance in comparison to typical commercial solutions in the field while being more economical and versatile due to its open source platform.

Our laser current...

Highly charged ions (HCI) have many favorable properties. They offer a high sensitivity to test fundamental physics and for the search of new physics, a simplified atomic structure due to a small number of bound electrons, and a low susceptibility to external perturbing fields [1]. Therefore, HCI are also well-suited for next-generation optical atomic clocks, which can in principle operate at...

Quantum electrodynamics (QED) is one of the most successful fundamental theories to date. With
the g-2 measurement of the free electron, QED interaction has been tested rigorously [1]. Using a
highly charged ion (HCI), one can similarly test bound-state QED effects. This allows to test the
interaction of the electron with the strong electric field present in the vicinity of the nucleus....

I will describe the basics of bound-state Quantum Electrodynamics (QED). I will focus on the interaction of a bound particle with an external magnetic field, parametrized by the g-factor. Recent developments in the theory of g-factors in low-Z ions will be described. Some developments in medium-Z and high-Z ions will also be discussed.

In this contribution, we discuss the quantum electrodynamic (QED) theory of strongly bound atomic systems. The ionic g factor can be measured nowadays to high precision with the combination of Penning traps and electron beam ion traps. The collaboration of theory and experiment enables impactful and detailed tests of QED in a strong background field, and a competitive determination of...

In ARTEMIS[1] laser-microwave double-resonance spectroscopy[2] will be used to measure the intrinsic magnetic moments of both electrons and nuclei in heavy, highly charged ions (HCIs). The extreme field strength of the nearby nucleus in such heavy HCIs enhances the effect of bound-state QED and nuclear interactions with the orbiting electron. Figure 1 shows the level scheme for hydrogen-like...

SpecTrap is part of the experiments located at HITRAP and aims at precision measurements of optical transitions in few-electron highly charged ions as a means of testing QED predictions in the regime of extreme electromagnetic fields. Particularly, focus is on spectroscopy of hyperfine transitions in hydrogen- and lithium-like ions that are cooled and confined in the cryogenic Penning trap. I...

The Jena Atomic Calculator (JAC) provides an easy-to-use but powerful toolbox to extent atomic theory towards new applications. It has been designed to be equally accessible for working spectroscopists, theoreticians and code developers. In this talk, I shall discuss the recent progress in developing these tools towards different cascade and second-order processes which are relevant for...

Precision isotope-shift spectroscopy of ions provides a very promising tool to probe the fundamental limits of Standard Model and to search for hypothetical "fifth-force" interactions. The analysis of the isotope-shift experimental and theoretical results can be performed most conveniently by means of the so-called King plot (KP). In this plot, the normalized frequency shifts of two (or even...