H. F. Beyer

Measurement of the ground-state lambshift of hydrogenlike uranium at the electron cooler of the ESR

X-rays are emitted with the radiative recombination of free electrons in an electron cooler of a heavyion storage ring. Due to a small width of the X-ray lines, an observation angle close to 0° and an accurate determination of the ion velocity, the ground-state Lambshift of hydrogenlike uranium (470 ± 16) eV could be measured to an accuracy of 3.4%. A re-evaluation of a measurement of the 1s1/2 Lambshift in hydrogenlike gold gave a new value of (202.3 ± 7.9) eV as compared to the former value of (212 ± 15) eV. The results are in excellent agreement with QED calculations and are more precise than any other measurements previously reported for a high-Z, hydrogenlike ion.

Characterization of transmission-type curved-crystal X-ray optics for fast ion-beam spectroscopy

Abstract The behavior of curved-crystal X-ray spectrometers in combination with fast moving sources is studied. A three-dimensional Monte-Carlo ray-tracing calculation is presented for cylindrically bent crystals used in transmission. The method allows an accurate calculation of two-dimensional line shapes and of geometrical aberrations. The geometrical formulae derived can be used for the design of spectrometers and for the analysis of experiments. For some limiting cases analytical expressions for the X-ray images are given and compared with the numerical calculations.

Status and perspectives of atomic physics research at GSI: The new GSI accelerator project

A short overview on the results of atomic physics research at the storage ring ESR is given followed by a presentation of the envisioned atomic physics program at the planned new GSI facility. The proposed new GSI facility will provide highest intensities of relativistic beams of both stable and unstable heavy nuclei - up to a Lorentz factor of 24. At those relativistic velocities, the energies of optical transitions, such as for lasers.. are boosted into the X-ray region and the high-charge state ions generate electric and magnetic fields of exceptional strength. Together with high beam intensities a range of important experiments can be anticipated, for example electronic transitions in relativistic heavy-ion collisions such as dynamically induced e(+)e(-) pairs, test of quantum electrodynamics (QED) in strong fields, and ions and electrons in ultra-high intensity femtosecond laser fields

Excited States of Few-Electron Recoil Ions from Ion Impact on Neon Studied by X-Ray and Electron Measurements

Neon K Auger-electron and X-ray spectra have been measured for various incident ions (Cl to U) and for different velocities (0.3-9 MeV amu-1). The degree of ionization of the L shell increases with increasing charge of the ion and decreases with increasing velocity, and it is represented as function of the projectile velocity divided by charge. Electron capture into metastable, highly charged neon recoil atoms proceeds in a highly selective way to specific states, which are studied by measuring delayed emission from gas mixtures. Delayed neon X-ray spectra induced by 0.6-0.7 MeV amu-1 Cl10+ are presented. A classical model, using the ionization potential for the captured electron and the subshell specific binding energy in highly charged ions, explains the Rydberg state and estimates the cross section for the observed electron capture.

Observation of hydrogenlike and heliumlike krypton spectra

Hydrogenlike and heliumliken=2→n=1 lines in Kr have been produced and studied for the first time. HydrogenlikeL y α lines have been observed and the fine structure interval has been determined. The absolute energy of the1P1,3P2,3P1 lines of heliumlike Kr have been measured and compared to Multiconfigurational Dirac-Fock Calculations.

SPARC: The Stored Particle Atomic Research Collaboration At FAIR

The future international accelerator Facility for Antiproton and Ion Research (FAIR) encompasses 4 scientific pillars containing at this time 14 approved technical proposals worked out by more than 2000 scientists from all over the world. They offer a wide range of new and challenging opportunities for atomic physics research in the realm of highly‐charged heavy ions and exotic nuclei. As one of the backbones of the Atomic, Plasma Physics and Applications (APPA) pillar, the Stored Particle Atomic Physics Research Collaboration (SPARC) has organized tasks and activities in various working groups for which we will present a concise survey on their current status.

Applications of position sensitive germanium detectors for X-ray spectroscopy of highly charged heavy ions

The spectroscopy of atomic transitions in the hard X-ray regime above 15 keV utilizing position-sensitive solid state detectors is discussed. Special emphasis is given to the current detector developments for X-ray spectroscopy of heavy ions at the ESR storage ring where applications for precision spectroscopy as well as for polarization studies are of particular interest. For both cases, the advantages and new possibilities which are opened up by position and energy resolving solid state detectors are illustrated by the presentation of first experiments.

Electron bremsstrahlung in collisions of 223 MeV/ u He-like uranium ions with gaseous targets

The bremsstrahlung process in the domain of strong Coulomb fields has been investigated for and Ar target electrons colliding with He-like uranium ions at . The differential cross sections for bremsstrahlung were measured at laboratory observation angles of , , and . Substantial discrepancies were found between the experimental cross sections and the first-order Born approximation calculations. The reported data provide a new testing ground for non-perturbative treatment of the coupling between radiation and matter in the presence of strong fields.

Ray tracing of curved-crystal X-ray optics for spectroscopy on fast ion beams

Abstract A method of ray tracing is presented which allows a detailed analysis of the X-ray line profile observed with a curved-crystal spectrometer for both a stationary or a fast X-ray source. In particular, the effect of finite dimensions of crystal and source and their interplay with a finite velocity vector of the source is discussed for Johann and Johansson spectrometers. It is shown how some parameters cause distortions and shifts of the reflection and how far they can be resolved by using a two-dimensional position-sensitive X-ray detector.

Precision tests of QED in strong fields: experiments on hydrogen- and helium-like uranium

In this contribution, we present an experimental study carried out at GSI Darmstadt devoted to investigation of quantum electrodynamical (QED) effects for the ground states in hydrogen- and helium-like uranium. In the experiment, X-ray spectra following radiative recombination of free electrons with bare and H-like uranium ions (U92+, U91+) were measured at the electron cooler of the ESR storage ring. Utilizing clean and favorable experimental conditions present at the electron cooler, we were able to obtain very accurate values for the ground-state binding energies from the observed X-ray transitions. When compared with theory, our results provide the most stringent test of bound-state QED for one- and two-electron systems in the strong-field regime.