The ultimate scheme for laser cooling of stored relativistic ions is to use a bunched ion beam and 3 independent laser beams. Here, the entire longitudinal momentum distribution of the ion beam should be addressed simultaneously using the unique combination of one cw and two pulsed laser beams*. Each beam will be produced by a separate laser system, but the 3 laser beams are all in the UV...
We propose a new measurement for the precise determination of the 2s1/2 →2p3/2 transition energy in Li-like uranium by means of resonant coherent excitation of ions in a thin Si-crystal. The goal of the proposed measurement is to determine the transition energy with an accuracy of the order ppm by a more precise determination of the ion beam energy. Also the RCE in non-channeling conditions...
Here we propose to measure the fundamental atomic process of electron-impact excitation (EIE) for the heaviest helium-like ion (U90+) at the gas-jet target of the ESR. Thereby we plan to extend the previous successful study where the EIE process has been identified for the first time for such a system, but only relative cross sections could be extracted and compared to theory. In the proposed...
Laser cooling has been successfully demonstrated at the ESR, using bunched beams of Li-like carbon ions at 47% of the speed of light. We now wish to explore the limits in terms of particle number (stored ions), temperature (relative momentum spread) and stability (over time) more carefully. We propose to study these using a "chain" of stored ions in the ESR. In addition, we wish to study a...
The proposed experiment is aiming at the first high-resolution measurement of the exotic, dipole allowed, "two-electron one-photon" decay (TEOP) of the $1s(2s)^2$ state in the heaviest Li-like ion ($U^{89+}$). This transition is mediated by electron-electron correlation and in lithium-like uranium it is (surprisingly) expected to be the dominant decay mode. However, it is entwined with an M1...
[Resubmission E133]
High density low-Z droplet target beams have been realized at the Experimental Storage Ring (ESR) since many years. In the course of the past beamtimes the droplet target source underwent a thorough characterization. However, a puzzling observation was made in the course of the optical imaging of the interaction region. Occasionally, bright light traces appeared on the...
[E135 -resubmission]
Our proposal was first presented to the G-PAC in 2010 (rank A, 21 shifts). It was resubmitted for re-evaluation in 2017 (rank A-, 21 shifts). We had a “test beamtime” (shared with S467) at the ESR from the 20th until the 25th February 2020. It was 13½ shifts long, but effectively we could use only 12 shifts. The ion beam was isotope 86Kr, not 84Kr.
We have made great...
We propose to follow up on our previous study E117 of the dynamics of the projectile ionization for multi-electron heavy ions with near relativistic velocities
U28+ + A → U(28+n)+ + {A+*} + n e-(≈00-cusp)
by developing instrumentation for coincident detection of upcharged Uq+(29<q<45) inside the dipole following the jet target. This module is based on successful position sensitive...
Continuation of E142.
The "nuclear clock" isomeric state 229-Thorium with its exceptional low excitation energy of around 8.3 eV is in the research focus of many laboratories worldwide.
At GSI, an alternative approach to the physics of 229-Th is under development: We propose to investigate and utilize a phenomenon that is unique to very highly charged 229Th such as one-electron 229Th89+....
We propose to measure the lifetime of short-lived excited states in Be-like Carbon by a pump-probe experiment. Utilizing two synchronized and delayed Femtosecond XUV pulses allows accessing these lifetimes with Femtosecond precision for the first time. These measurements will provide sensitive tests of state-of-the art atomic structure calculations beyond the capabilities of established...
We intend to submit a proposal to measure the reaction 91Nb(p,g)92Mo in ESR as a continuation of the proton-capture campaign that has been very successful in the recent past. 91Nb is a radionuclide, which in a first step has to be produced in FRS using a primary beam of 94Mo or similar. Furthermore, accumulation, cooling and deceleration in the ESR down to energies of 5-10 MeV/u are needed, as...
Radiative electron capture (REC), the time reversed photon ionization process in ion–atom collisions, has been studied in great detail for projectile nuclear charges covering virtually the whole periodic table of elements up to fully stripped uranium ions [1]. With regard to the beam energies, the available data span from the low-collision energy regime up to high relativistic energies of...
In extremely hot and dense astrophysical plasmas, high-Z atomic nuclei become highly ionized and the nucleus can couple to the atomic system via processes like electron capture (NEEC) or electronic transition, resulting in the nucleus being in an excited state, which can affect nuclear properties in scenarios like the r process. The NEEC rate is presently controversial, with a claimed...
We propose here an evolution of the past E125 proposal that uses H-like scandium as reference line and a smaller gas-jet target (from 5 to 1 mm) to measure the $1s_{1/2}2p_{3/2}\,J$=2 $\to1s_{1/2}2s_{1/2}\,J$=1 intrashell transition in He-like uranium. This improvement will allow to reach the accuracy of 10~meV for the 4.5~keV line, sufficient to start to be sensitive to three-loop and more...
The experimental study of slow Xe54+ + Xe collisions has been defined in the “Physics book: CRYRING@ESR” as an intermediate milestone on the path towards heavy quasi-molecular collision in supercritical fields. In our recently published investigation of Xe54+ + Xe collisions at 30 and 15 MeV/u performed at the ESR, we learned valuable lessons for the experimental feasibility of such studies....
The measurement of the ground-state hyperfine structure in H-like and Li-like highly charged ions is supposed to provide the best test of QED in the strong magnetic field regime. The measurement of both charge states is required to remove nuclear structure uncertainties, originating in the magnetic dipole moment distribution inside the nucleus (Bohr Weisskopf effect). Such a test has been...
Beta-decay properties of highly-charged ions can differ significantly from the ones known in neutral atoms. Here, we propose to investigate the dependence of the nuclear electron capture rate in fully-ionized, hydrogen-like, and helium-like $\mathrm{^{64}Cu}$ ions at the FRS-ESR facility by employing the time-resolved Schottky mass spectrometry.
The present proposal was evaluated with grade...
Spectroscopic data from astronomical observations obtained at ground-based or satellite observatories are analyzed with the help of spectral synthesis codes. From complex rate equation networks, based largely on theoretical plasma rate coefficients of various up- and downcharging processes, a charge state distribution is modelled and emission and absorbtion features synthesized and matched to...
In 2017, the LIGO/Virgo collaboration detected the first gravitational-wave signal from the merger of a neutron-star binary. Less than two seconds later, a network of telescopes detected a short gamma-ray burst, followed by a longer optical “afterglow” powered by the radioactive decay of the neutron-rich material ejected in the merger, i.e., a kilonova. The kilonova light-curves potentially...
A BMBF-funded free-electron target for GSI’s/FAIR’s storage rings that operates in transverse collision geometry, i.e., with an interaction angle of 90◦ between electrons and stored ions, is presently being built up and tested at the University of Giessen. The target is intended as a user facility for electron-ion collision experiments and x-ray spectroscopy with free electrons. Originally, it...
Electronic processes in ion-ion collisions are of fundamental interest from atomic physics point of view and they play an important role in astrophysical and fusion plasmas as well as in ion-matter interaction. At the same time, the ion-ion collisions are mostly unexplored up to now. This is especially true for the so-called intermediate velocity regime where the ion stopping power is maximum,...
The feasibility of high-resolution electron-ion collision spectroscopy at CRYRING@ESR of few-electron highly-charged ions from the GSI chain of accelerators has been demonstrated in a previous beam time (E131) in March 2021. In particular, it was shown that the electron-energy spread at the CRYRING electron cooler is indeed as low as expected. Building on this success, our collaboration will...
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 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 are currently no data available to challenge...
The proposal for measuring the reaction Ti-44(α,p)V-47 at CRYRING@ESR was granted beam time for the year 2022 in the last G-PAC (E151). However, due to various delays neither the internal gas target nor the CARME detector setup was ready and fully commissioned for successfully performing the proposed beam time. A first commissioning beam time could be performed in spring this year with one...
CARME has been successfully commissioned with beam at CRYRING in February-March 2022, in spite of some issues with the newly mounted internal target. Its science programme will be supported by an ERC Starting Grant going forward.
I will discuss our plans for the future, in terms of re-submitting proposals that have already been accepted (e.g. 2H+1H), and the potential to submit new...
We propose a systematic measurement of electron capture cross sections for heavy, bare ions at projectile energies below 5.5 MeV/u at different parameters, namely the projectile charge number, the collision energy and the target charge number. The measurement will be realized by introducing a novel internal target station setup to the CRYRING@ESR. The required diagnostic tools will be three...
One of the physics cases motivating the construction of CRYRING at the ESR was the search for NEEC through neutralization of highly-charged ions in nuclear isomeric states. The isomer of interest is 129Sb or 93Mo.
We want to continue laser spectroscopy experiments at CRYRING@ESR with Mg$^+$ ions in order to study population dynamics in the ions as well as electron-cooler ion beam dynamics.
Synchrotron oscillations in bunched beam operation lead to fast hyperfine level pumping of all velocity classes within a few revolutions. This surprising behaviour shall be further studied using laser intensity...
We propose to measure x-ray fluorescence following charge exchange between bare Xe$^{54+}$ ions and different gas targets at ultra-low collision energies at HITRAP. By detecting fluorescence in coinicidence with projectile ions, and recording ion time-of-flight, reaction channels can be separated. This will provide charge-exchange data for an energy regime inaccesible in storage ring setups,...
Upon impact on a surface, slow highly charged ions (HCIs) deposit large amounts of their potential energy within the first few monolayers of the material. Depending on material properties relaxation processes can lead to nanosized material modifications, e.g. hillocks and craters in bulk samples or pores in 2D materials - often in a similar manner as after swift heavy ion (SHI) impact. For...
With use of collisional spectroscopy at the electron cooler and with a ions from
local ion source we would like to investigate DR and intrashell TR processes.
Mainly:
Be-like S$^{12+}$ + e$^-$ → S$^{11+}$
Here, resonances:
DR 2s$^2$→2s$^1$2p$^2$ and TR 2s$^2$→2p$^3$ (collisional energy <1.2eV)
DR 1s$^2$2s$^2$→1s$^1$2p$^2$ and TR 1s$^2$2s$^2$→1s$^1$2p$^3$ (collisional energy ~2000eV)
