Towards an Intrinsic Doppler Correction for X-ray Spectroscopy of Stored Ions at CRYRING@ESR

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron cooler of CRYRING@ESR at GSI, Darmstadt, Germany. The X-ray emission associated with the radiative recombination of cooler electrons and stored hydrogen-like uranium ions was investigated using two novel microcalorimeter detectors positioned under 0∘ and 180∘ with respect to the ion beam axis. This new experimental setup allowed the investigation of the region of the N, M → L transitions in helium-like uranium with a spectral resolution unmatched by previous studies using conventional semiconductor X-ray detectors. When assuming that the rest-frame energy of at least a few of the recorded transitions is well-known from theory or experiments, a precise measurement of the Doppler shifted line positions in the laboratory system can be used to determine the ion beam velocity using only spectral information. The spectral resolution achievable with microcalorimeter detectors should, for the first time, allow intrinsic Doppler correction to be performed for the precision X-ray spectroscopy of stored heavy ions. A comparison with data from a previous experiment at the ESR electron cooler, as well as the conventional method of conducting Doppler correction using electron cooler parameters, will be discussed

Measurement of the bound-state beta decay of bare 205Tl81+ ions at the ESR

Ever since the construction of the Experimental Storage Ring (ESR) at GSI, measurement of the bound-state beta decay of 205Tl81+ ions was one of the main physics cases to be performed. Bound-state beta decay (βb), is a particular weak interaction decay mode, in which the electron remains in a bound atomic state rather than being emitted into the continuum, which is favored in the case of highly-ionized atoms. In this thesis, I report on the first measurement of the bound-state beta decay of fully-ionized 205Tl81+ ions. For the experiment, 205Tl81+ ions were produced via the projectile fragmentation of a primary 206 Pb beam in the FRagment Separator (FRS), which were well separated from the 205Pb81+ contaminants by using the Bρ-∆E-Bρ technique. 205Tl81+ ions were then accumulated, stochastically and electron cooled, and stored for different storage times in the ESR in order to determine the half-life. The obtained value is 229±36 days which agrees within 3σ with the theoretically predicted value of 122 days. The measurement is essential for two physics cases. The first one is linked with the LOREX project (acronym of LORandite EXperiment), wherein, the measurement is needed to determine the nuclear matrix element of the solar pp neutrino capture by the ground state of 205Tl to the 2.3 keV excited state in 205Pb. With the longer measured half-life, the nuclear matrix element will become smaller which is pivotal for the solar pp neutrino studies. The second physics case is associated with the 205Pb/205Tl pair as an s-process cosmochronometer. In stellar medium, 205Tl can exist in the ionized form and βb decay to the first excited state of 205Pb can counter-balance the reduction of 205Pb ions due to the electron capture process. Smaller destruction of 205Tl is expected in the stellar plasmas due to the longer measured half-life of βb decay. This is crucial for the clarification of the fate of 205Pb in the early solar system

Electroweak Decays of Highly Charged Ions

In this contribution we review the present status of experimental studies of electroweak decays of highly charged ions. A particular focus will be given on the bound state beta decay measurement of 205Tl

Analysis methods to determine the bound-state beta-decay half-life of Thallium-205

Bound-state β−-decay is an exotic decay mode that produces temperature-dependent stability in nuclei. A striking example is 205Tl, in part because of its impact on the 205Pb/204Pb cosmochronometer—a short-lived ra-dionuclide clock that can provide unique constraints on s process material in the early solar system. The bound-state β−-decay of 205Tl was measured at GSI, where fully stripped 205Tl81+ ions were produced and stored in the Experimental Storage Ring. Decay occurred during storage producing increased 205Pb daughters with increased storage time. This contribution briefly outlines the experiment and describes analytical corrections required to extract the half-life

Single and double KK-shell vacancy production in slow Xe54+,53+Xe^{54+,53+} -Xe collisions

We present an experimental and theoretical study of symmetric $\textrm{Xe}^{54+}+\textrm{Xe}$ collisions at 50, 30, and 15 MeV/u, corresponding to strong perturbations with $v_K/v_\text{p}$ = 1.20, 1.55, and 2.20, respectively ($v_K$: classical $K$-shell orbital velocity, $v_\text{p}$: projectile velocity), as well as $\textrm{Xe}^{53+}+\textrm{Xe}$ collisions at 15 MeV/u. For each of these systems, x-ray spectra were measured under a forward angle of $35^\circ$ with respect to the projectile beam. Target satellite and hypersatellite radiation, $K\alpha_{2,1}^\mathrm{s}$ and $K\alpha_{2,1}^\mathrm{hs}$, respectively, were analyzed and used to derive cross section ratios for double-to-single target $K$-shell vacancy production. We compare our experimental results to relativistic time-dependent two-center calculations.Comment: 8 pages, 4 figure

[NOCH-AP-Experiment fehlt] X-ray emission associated with radiative recombination for Pb82+Pb^{82+} ions at threshold energies

For bare lead ions, decelerated to the low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at "cold collision" conditions has been studied at the electron cooler of CRYRING@ESR at GSI-Darmstadt. Utilizing dedicated x-ray detection chambers installed at 0{\deg} and 180{\deg} observation geometry, we observed for the very first time for stored ions the full x-ray emission spectrum associated with RR under electron cooling conditions. Most remarkably, no line distortion effects due to delayed emission are present in the well resolved spectra, spanning over a wide range of x-ray energies (from about 5 to 100 keV) which enable to identify fine-structure resolved Lyman, Balmer as well as Paschen x-ray lines along with the RR transitions into the K-, L and M-shell of the ions. To compare with theory, an elaborate theoretical model has been applied. By considering the relativistic atomic structure of Pb$^{81+}$, this model is based on a sophisticated computation of the initial population distribution via RR for all atomic levels up to Rydberg states with principal quantum number $n=$ 165 in combination with cascade calculations based on time-dependent rate equations. Within the statistical accuracy, the experimental x-ray line emission is in very good agreement with the results of the theoretical model applied. 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