A low-energy storage ring with an ultracold electron cooler has been coupled with a heavy-ion accelerator facilitating high-resolution electron-ion collision spectroscopy of the heaviest few-electron ions. In the present Letter resonant electron-ion recombination of berylliumlike Pb^{78+} ions was measured in the collision-energy range 9.3-16.5 eV and a value of 244.937(30) eV is derived for the Pb^{78+}(2s^{2} ^{1}S_{0}-2s2p ^{3}P_{1}) excitation energy. This result agrees with the most recent (less accurate) theoretical value of 244.942(52) eV [Malyshev et al., Phys. Rev. A 110, 062824 (2024)PLRAAN2469-992610.1103/PhysRevA.110.062824], which has been calculated by applying strong-field QED rigorously up to the second order. The present investigation suggests that further technical improvements can potentially increase the experimental accuracy by an order of magnitude.

We have tested operation of FAIR’s low-energy ion storage ring CRYRING@ESR with uncompensated electron cooler solenoid. With its standard working point on the lowest-order difference resonance, a second solenoid is normally used to cancel betatron coupling introduced by the cooler’s magnetic field. In operation with a D + test beam, we found that omission of the compensation solenoid did not lead to a notable deterioration of beam intensity, quality, or cooling time, though the expected coupling of betatron motion is then clearly observed.

For decelerated bare lead ions at a low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at threshold energies has been studied at the electron cooler of CRYRING@ESR at GSI, Darmstadt. In our experiment, we observed the full x-ray emission pattern by utilizing dedicated x-ray detection chambers installed at 0??? and 180??? observation geometry. Most remarkably, no line distortion effects due to delayed emission are present in the well-defined x-ray spectra, spanning a wide range of x-ray energies (from about 5 to 100 keV), which enables us to identify fine-structure resolved Lyman, Balmer, and Paschen x-ray lines along with the RR transitions into the K, L, and M shells of the ions. For comparison with theory, an elaborate theoretical model is established taking into account the initial population distribution via RR for all atomic levels up to Rydberg states with principal quantum number n = 165 in combination with time-dependent feeding transitions. Within the statistical accuracy, the experimental data are in very good agreement with the results of rigorous relativistic predictions. Most notably, this comparison sheds light on the contribution of prompt and delayed x-ray emission (up to 70 ns) to the observed x-ray spectra, originating in particular from yrast transitions into inner shells.

The CRYRING@ESR facility [1] will provide the unique possibility for studying properties of highly charged cooled stable and short-lived ions stored at low energy for atomic and nuclear research within the FAIR project [2]. Heavy ion beams will be stored, cooled and decelerated to energies between 10 and 4 MeV/u in the ESR [3] and then delivered to the CRYRING@ESR. There is no dedicated kicker magnet for the fast extraction in this direction. However, a specially developed distorted closed orbit of the beam stored in the ESR in combination with the injection kicker has been suggested for the extraction and experimentally verified in 2014. In the first experiment the ion beam was extracted and transported over a distance of 20 m towards the CRYRING@ESR [4]. In the 2016 machine development run the heavy ion beam was successfully extracted from the ESR and delivered to the first fluorescent screen inside CRYRING@ESR for the first time. Detailed ion-optical simulations as well as the experimental results will be discussed.

Once operational, CRYRING@ESR will store and decelerate ions delivered by the experimental storage ring ESR at energies well below those of ESR. In addition to that, CRYRING@ESR has an electron cooler operating with an ultracold electron beam, allowing to provide cooled ion beams for precision experiments. These ions will be delivered to a broad range of experiments presently in preparation; either in-ring or extracted to a dedicated beamline for experiments. An overview and status report of the installation and commissioning of the CRYRING-@ESR storage ring for highly charged ions at the GSI Helmholtzzentrum für Schwerionenforschung is presented. The installation of this storage ring started in 2014 and was completing end of 2016, when this publication was written.

Although different ion-atom collisions have been studied in various contexts, precise values of cross-sections for many atomic processes were seldom obtained. One of the main uncertainties originates from the value of target densities. In this paper, we describe a unique method to measure a target density precisely with a combination of physical vapor deposition and inductively coupled plasma optical emission spectrometry. This method is preliminarily applied to a charge transfer cross-section measurement in collisions between highly charged ions and magnesium vapor. The final relative uncertainty of the target density is less than 2.5%. This enables the precise studies of atomic processes in ion-atom collisions, even though in the trial test the deduction of precise capture cross-sections was limited by other systematic errors.

We report an experimental study of the charge-transfer process in collisions of Xeq+ ions (16 <= q <= 20) with magnesium atoms at an energy of 5.5q keV. With charge-selective and time-coincidence techniques, we separated the pure capture and capture accompanied by transfer-ionization processes. The experimental data indicate that the magnesium target is around two times more likely to lose two electrons than one in the collision. This finding is very different compared to the calculation based on the extended classic over-the-barrier model. The Xeq+-Mg collision also behaves very differently from "traditional" collisions between highly charged ions and noble gases. We suggest a one-step dielectronic mechanism for the capture process. The data also show that autoionization dominates the relaxation process after the capture, and fluctuation of the autoionization fraction versus the projectile charge state indicates that for the relaxation processes, the projectile core structure plays a more important role than the detailed characteristics of the projectile states where the target electrons are initially captured.

An Electron Beam Ion Trap was installed at GSI Darmstadt, where it will be used for tests and offline measurements of components and experiments of SPARC (Stored Particle Atomic physics Research Collaboration) like HITRAP. The design of the so called SPARC-EBIT is based on a Helmholtz-pair of permanent magnets for electron beam compression. This results in a very compact room temperature source for highly charged ions (HCI), which is portable and simple to operate. To characterize the performance of the EBIT, X-ray and time-of-flight (TOF) spectra were recorded and also time-dependent current measurements were performed. For detection of X-rays from the interaction region a Silicon-pin diode was installed in front of the EBIT's beryllium window. The analysis of the in pulsed mode extracted ions was done with an achromatic TOF spectrometer, placed on the other end of a short test beam. With these investigation methods typical extraction pulses with argon ions were observed, from which the trap capacity and the effective trap length could be determined. The time-dependent charge state development of argon and krypton were studied depending on confinement time, axial trap depth and trap pressure with different measurement methods and the results were compared. In addition, simulations with CBSIM show the agreement between experimental achievements and theory and allow the determination of significant characteristics of the SPARC-EBIT.

The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes No252-254 were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a Ca-48 beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

Highly charged ions (HCIs) are an important tool in various fields of basic and applied physical research. However, in many cases the species of interest cannot be produced directly by a primary ion source. Therefore, charge breeding, i.e. the conversion of singly charged ions to highly charged ions, is an essential part of projects such as nuclear or astrophysical experiments with post accelerated beams of radioactive ions [1] or precise nuclear mass measurements with ions stored in penning traps [2]. At GSI’s HITRAP facility [3] HCIs up to U92+ can be provided using an accelerator complex to strip electrons of f the initially low charged ions at high velocities. In case the beam from the accelerator structure is not available, tests can be run using a compact room-temperature electron beam ion trap, the SPARC-EBIT [4], which was designed to produce HCIs from gaseous materials injected through a needle valve. To broaden the range of particles which can be fed to the source we have investigated its abilities as a charge breeder. The setup for the charge breeding experiments includes a surface ion source for the creation of the singly charged alkali metal ions. The measurements presented in this paper were performed using potassium. These primary ions are guided straight towards the SPARC-EBIT where the charge breeding process takes place. It can be divided into three phases: K 1+ injection, breeding, and re-extraction of a pulse of highly charged ions from the EBIT. During the re-extraction phase a quadrupole bender mounted in between the two ion sources is switched from ground to high voltage to bend the ion trajectories by 90 degrees and send the pulse towards the multi passage spectrometer (MPS) where it can then be analyzed by magnetic A/q separation. A typical A/q spectrum of charge bred potassium measured with the MPS is presented in figure 1. The source parameters given in the picture were found to be optimal for continuous potassium ion injection. After a breeding time of tbreed= 3 s the charge state distribution has reached its equilibrium. Since the electron beam energy of the EBIT was set close to the ionization energy of the K-shell, helium-like potassium shows the highest relative abundance in the spectrum. Bare potassium ions have been detected, though only in small amounts. Further on, it was discovered that an injection time of tinj = 20 ms at the beginning of the breeding time, tbreed, is sufficient to achieve the maximum ion output for high charge states. The capture efficiency during the measurement resulted in ≈ 2·10−4. Breeding efficiencies for different charge states

The SPARC-EBIT (fig.1) is an Electron Beam Ion Trap (from DREEBIT, Dresden) that will be used for tests and offline measurements, firstly for HITRAP, and later for SPARC (Stored Particle Atomic physics Research Collaboration). In the EBIT the ions are produced by electron impact ionisation of gas atoms by an intense electron beam. The magnetic field of a permanent magnet arrangement focuses the beam and guides it through the ionisation chamber. This design makes the EBIT portable and simple to operate.

The cross section for that process is σq,q−p r . Within the main process we can distinguish three different sub processes, electron capture ( r − p = 0), ionization transfer (r − p > 0) and ionization ( p = 0, andr > 0). The latter is negligible for the here studied velocity regime.. The setup is shown schematically in Fig. 1. Highly charged xenon ions ( Xe) were extracted from an electron beam ion trap at GSI [1] with an energy of 5.5 q keV continuously. After charge to mass selective bending, the ion beam collided with the magnesium vapor produced by an oven. Finally, the projectiles were dispersed by another bending magnet to separate primary ions and ions with one or more captured electrons, recorded by a position sensitiv e multi-channel plate (MCP) detector. The recoiled Mg r+

The MAXEBIS (MAX Electron Beam Ion Source) is an ion source optimized for the production of highly charged ions. Central part of the ion source is an IrCe filament driven electron gun. The electron beam is guided by a magnetic field (max 5T) of a superconducting solenoid. Through the longitudinal and transverse confinement the EBIS ion source is ideal for charge states breeding proc- ess of externally injected ions as it is used for radioactive beam facilities like CERN/ISOLDE. The MAXEBIS (1) has at present two tasks. It is used as a test injector for the HITRAP cooler trap (2), which is an essential part of the HITRAP project and for offline tests of the whole low energy beam line. This setup is prepared outside GSI at the Heckhalle. After the test period the MAXEBIS will be moved to GSI, and will be included in the HITRAP beam line as an offline and test injector dur- ing GSI accelerator shutdowns or for commissioning pur- poses. The second task is dedicated to investigations of advanced charge breeding methods in the framework of EURONS und EURISOL-DS (European Isotope Separa- tion On-Line Radioactive Ion Beam Facility). Here the goal is to apply known ion source techniques in order to improve the critical charge breeding issues, like effi- ciency, beam quality and purity. In 2006 the MAXEBIS setup has been completed and became operational for magnetic mass analysis and exter- nal injection using a surface ion source and an Ar-sputter gun. The completed setup is shown in figure 1.