Doppler-tuned Bragg Spectroscopy of Excited Levels in He-Like Uranium: a discussion of the uncertainty contributions

We present the uncertainty discussion of a recent experiment performed at the GSI storage ring ESR for the accurate energy measurement of the He-like uranium 1s2p3P2- 1s2s3S1 intra-shell transition. For this propose we used a Johann-type Bragg spectrometer that enables to obtain a relative energy measurement between the He-like uranium transition, about 4.51 keV, and a calibration x-ray source. As reference, we used the Ka fluorescence lines of zinc and the Li-like uranium 1s22p2P3/2 - 1 s22s 2S1/2 intra-shell transition from fast ions stored in the ESR. A comparison of the two different references, i.e., stationary and moving x-ray source, and a discussion of the experimental uncertainties is presented

Doppler-tuned Bragg Spectroscopy of Excited Levels in He-Like Uranium: a discussion of the uncertainty contributions

We present the uncertainty discussion of a recent experiment performed at the GSI storage ring ESR for the accurate energy measurement of the He-like uranium 1s2p3P2- 1s2s3S1 intra-shell transition. For this propose we used a Johann-type Bragg spectrometer that enables to obtain a relative energy measurement between the He-like uranium transition, about 4.51 keV, and a calibration x-ray source. As reference, we used the Ka fluorescence lines of zinc and the Li-like uranium 1s22p2P3/2 - 1 s22s 2S1/2 intra-shell transition from fast ions stored in the ESR. A comparison of the two different references, i.e., stationary and moving x-ray source, and a discussion of the experimental uncertainties is presented

Doppler-tuned Bragg Spectroscopy of Excited Levels in He-Like Uranium: a discussion of the uncertainty contributions

We present the uncertainty discussion of a recent experiment performed at the GSI storage ring ESR for the accurate energy measurement of the He-like uranium 1s2p3P2- 1s2s3S1 intra-shell transition. For this propose we used a Johann-type Bragg spectrometer that enables to obtain a relative energy measurement between the He-like uranium transition, about 4.51 keV, and a calibration x-ray source. As reference, we used the Ka fluorescence lines of zinc and the Li-like uranium 1s22p2P3/2 - 1 s22s 2S1/2 intra-shell transition from fast ions stored in the ESR. A comparison of the two different references, i.e., stationary and moving x-ray source, and a discussion of the experimental uncertainties is presented

A 2D position sensitive germanium detector for spectroscopy and polarimetry of high-energetic x-rays

We report on a first prototype 2D μ-strip germanium detector, developed at IKP-Jülich, and its performance test at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Beside an accurate determination of the detector response function, the polarization sensitivity has been addressed in this study. For this purpose photon beams at energies of 60 keV and 210 keV have been used

Beam lifetimes and ionization cross sections of U28+^{28 +}

Beam lifetimes of stored U^{28+} ions with energies between 10 and 180  MeV/u were measured in the heavy ion synchrotron SIS18 and in the experimental storage ring (ESR) of the GSI accelerator facility. By using the internal gas jet target of the ESR, it was possible to obtain projectile ionization cross sections for collisions with H_{2} and N_{2} from the lifetime data. The experimental cross sections are compared to theoretical data predicted by the n-body classical-trajectory Monte Carlo (CTMC) method of Olson et al. and to calculations of Shevelko et al. using the LOSS-R code. In addition, both theoretical approaches are probed by using the resulting cross sections as input parameters for the STRAHLSIM code, which models the beam losses and, consequently, the lifetimes in the heavy ion synchrotron SIS18. Both the cross section measurement and the SIS18 lifetime study indicate that the LOSS-R code cross sections are in better agreement with the experimental results than the n-body CTMC calculations

Isotope shift in the dielectronic recombination of three-electron ^{A}Nd^{57+}

Isotope shifts in dielectronic recombination spectra were studied for Li-like ^{A}Nd^{57+} ions with A=142 and A=150. From the displacement of resonance positions energy shifts \delta E^{142,150}(2s-2p_1/2)= 40.2(3)(6) meV (stat)(sys)) and \delta E^{142,150}(2s-2p_3/2) = 42.3(12)(20) meV of 2s-2p_j transitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of ^{142,150}\delta = -1.36(1)(3) fm^2. The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.Comment: 10 pages, 3 figures, accepted for publication in Physical Review Letter

Subshell-selective x-ray studies of radiative recombination of U92+{\mathrm{U}}^{92+} ions with electrons for very low relative energies

Radiative recombination (RR) into the K shell and L subshells of U92+ ions interacting with cooling electrons has been studied in an x-ray RR experiment at the electron cooler of the Experimental Storage Ring at GSI. The measured radiative recombination rate coefficients for electron-ion relative energies in the range 0–1000 meV demonstrate the importance of relativistic effects. The observed asymmetry of the measured K-RR x-ray emission with respect to the cooling energy, i.e., zero average relative velocity (⟨vrel⟩=0), are explained by fully relativistic RR calculations. With our new approach, we show that the study of the angular distribution of RR photons for different relative energies opens new perspectives for detailed understanding of the RR of ions with cooling electrons in cold magnetized plasma

Differential energy measurement between He- and Li-like uranium intra-shell transitions

We present the first clear identification and highly accurate measurement of the intra-shell transition $1s2p\, ^3P_2 \to 1s2s\, ^3S_1$ of He-like uranium performed via X-ray spectroscopy. The present experiment has been conducted at the gas-jet target of the ESR storage ring in GSI (Darmstadt, Germany) where a Bragg spectrometer, with a bent germanium crystal, and a Ge(i) detector were mounted. Using the ESR deceleration capabilities, we performed a differential measurement between the $1s2p\, ^3P_2 \to 1s2s\, ^3S_1$ He-like U transition energy, at 4510 eV, and the $1s^22p\ ^2P_{3/2} \to 1s^22s\, ^2S_{1/2}$ Li-like U transition energy, at 4460 eV. By a proper choice of the ion velocities, the X-ray energies from the He- and Li-like ions could be measured, in the laboratory frame, at the same photon energy. This allowed for a drastic reduction of the experimental systematic uncertainties, principally due to the Doppler effect, and for a comparison with the theory without the uncertainties arising from one-photon QED predictions and nuclear size corrections

Observation of the 2p3/2 -> 2s1/2 intra-shell transition in He-like uranium

We present the first observation of the 1s2p 3P2 ? 1s2s 3S1 transition in He-like uranium. The experiment was performed at the internal gas-jet target of the ESR storage ring at GSI exploiting a Bragg crystal spectrometer and a germanium solid state detector. Using the 1s2 2p 2P3/2 ? 1s2 2s 2S1/2 transition in Li-like uranium as reference and the deceleration capabilities of the ESR storage rings, we obtained the first evaluation of the He-like heavy ion intra-shell transition energy