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A combination of the in-flight projectile fragment separator and the heavy-ion storage-cooler ring has been used to produce, store and investigate cooled highly charged ions. The results of recently performed experiments at GSI Darmstadt studying two-body β-decays of H-like and He-like ions are presented. The technique of Schottky lifetime spectroscopy has been applied to explore the electron capture and bound-state β- decay processes of ions circulating in the heavy-ion storage ring. [ABSTRACT FROM AUTHOR]

For the first time the electron capture and β+ decay rates of H-like 140Pr ions have been measured at the FRS-ESR facility by using the Schottky noise technique. The H-like 140Pr58+ decay rate was found to be larger by a factor of 1.5 than in the case of neutral atom. This non-intuitive result can be explained by taking into account hyperfine splitting of nuclear levels in the decaying nuclei and the conservation law of the total angular momentum of the system. [ABSTRACT FROM AUTHOR]

Abstract: The stopping of heavy ions at intermediate velocities is influenced by projectile screening, shell corrections, Barkas–Andersen effect and charge exchange. These effects are accounted for in the binary theory of stopping and implemented in the PASS code. Previous applications of this scheme have focused on ions up to argon. The present work is a first attempt to apply the PASS code to very heavy projectiles. It is known that as the ion/target atomic-number ratio increases, the stopping force becomes increasingly sensitive to the ionic charge state. Therefore, care has been taken to incorporate realistic mean charges based on experimental data. Calculated stopping cross sections are found to agree well with experiment at energies above ∼2MeV/u, while a systematic overestimate of up to 20% is found at lower projectile speeds. Possible causes are studied. Charge-state averaging is shown to have a significant effect at low speed. [Copyright &y& Elsevier]

Relativistic projectile fragmentation of208Pb has been used to produce isomers in neutron-rich,A˜ 190 nuclides. A forward-focusing spectrometer provided ion-by-ion mass and charge identification. The detection of ?-rays emitted by stopped ions has led to the assignment of isomers in188Ta,190W,192Re,193Re,195Os,197Ir,198Ir,200Pt,201Pt,202Pt and203Au, with half-lives ranging from approximately 10 ns to 1 ms. Tentative isomer information has been found also for174Er,175Er,185Hf,191Re,194Re and199Ir. In most cases, time-correlated, singles ?-ray events provided the first spectroscopic data on excited states for each nuclide. In200Pt and201Pt, the assignments are supported by ?-? coincidences. Isomeric ratios provide additional information, such as half-life and transition energy constraints in particular cases. The level structures of the platinum isotopes are discussed, and comparisons are made with isomer systematics. [ABSTRACT FROM AUTHOR]

The relative momentum spread of in-flight separated exotic nuclear beams produced in fragmentation and/or fission reactions is of the order of a few percent. A new technique is presented, which reduces the momentum spread significantly, and first experimental results obtained with relativistic projectile fragments are shown. This technique is the key to experiments with slowed-down and stopped beams, in particular for the efficient stopping of relativistic exotic nuclei in gas-filled stopping cells. It will be employed at the energy-buncher stage of the low-energy branch of the Super-FRS facility. The ion-optical design of the energy buncher is presented and a brief outlook to the experimental program is given. [Copyright &y& Elsevier]

A new long-lived isomeric state in the near proton dripline nucleus 125Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E * = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized 125 m Ce58+ ion. The data implies an E3 transition and a 1/2+ assignment for the spin of the isomer. [ABSTRACT FROM AUTHOR]

A novel system has been developed to detect simultaneous double-alpha emission from purified and weightless sources. The system includes the collection of 224Ra low-energy recoils in purified helium buffer gas from the decay of 228Th. The recoil products are thermalized and collected in a cryogenic buffer gas cell and extracted into an RF-ion guide for mass selection. The mass-separated ions are implanted at low kinetic energy into a thin carbon foil placed between two large-area double-sided silicon strip detectors to observe correlated alpha-particle emission. The apparatus is described in detail, including insights into its experimental performance. [ABSTRACT FROM AUTHOR]

Graphical abstract: Display Omitted Highlights: [•] We present the prospects for rare-isotope storage-ring measurements at FAIR. [•] A summary of present storage-ring capabilities is presented. [•] Access to the most exotic nuclides is provided using projectile fragmentation. [•] Masses and decay modes can be determined for highly-charged single ions. [•] Novel interactions at the atomic–nuclear interface are discussed. [ABSTRACT FROM AUTHOR]

At the FRS Ion Catcher (FRS-IC), projectile and fission fragments are produced at relativistic energies, separated in-flight, energy-bunched, slowed down, and thermalized in the ultra-pure helium gas-filled cryogenic stopping cell (CSC). Thermalized nuclei are extracted from the CSC using a combination of DC and RF electric fields and gas flow. This CSC also serves as the prototype for the CSC of the Super-FRS, where exotic nuclei will be produced at unprecedented rates making it possible to go towards the extremes of the nuclear chart. Therefore, it is essential to efficiently extract thermalized exotic nuclei from the CSC under high beam rate conditions, in order to use the rare exotic nuclei, which come as cocktail beams. The dependence of the extraction efficiency on the intensity of the impinging beam into the CSC was studied with a primary beam of 238U and its fragments. Tests were done with two different versions of the DC electrode structure inside the cryogenic chamber, the standard 1 m long and a short 0.5 m long DC electrode systems. In contrast to the rate capability of 10 4 ions/s with the long DC electrode system, results show no extraction efficiency loss up to the rate of 2 × 10 5 ions/s with the new short DC electrode. This order of magnitude increase of the rate capability paves the way for new experiments at the FRS-IC, including studies of exotic nuclei with in-cell multi-nucleon transfer reactions. The results further validate the design concept of the CSC of the Super-FRS, which was developed to effectively manage beams of even higher intensities. [ABSTRACT FROM AUTHOR]

Abstract: MOCADI, the Monte-Carlo code for tracking of ions in ion-optical systems with non-Liouvillian elements, has been extended. Accurate atomic and nuclear interactions are taken into account when ions penetrate gaseous and solid matter placed within the ion-optical system. The new features of MOCADI are described in this article with practical examples which demonstrate the new possibilities, such as new event-generators for targets and spontaneous nuclear decay, the option of atomic-charge state fluctuation in matter, loops for multi-turn ion-optical systems and a graphical user interface for easier operating and control of the program. Experiments for investigation of nuclear structure and reactions with ions circulating in a storage ring can now be ideally studied with MOCADI. [Copyright &y& Elsevier]

In this paper, the major upgrades and technical improvements of the buffer gas handling system for the cryogenic stopping cell of the FRS Ion Catcher at GSI/FAIR (in Darmstadt, Germany) are described. The upgrades include implementation of new gas lines and gas purifiers to achieve a higher buffer gas cleanliness for a more efficient extraction of reactive ions as well as suppression of the molecular background ionized in the stopping cell. Furthermore, additional techniques have been implemented for improved monitoring and quantification of the purity of the helium buffer gas. [ABSTRACT FROM AUTHOR]

Abstract: Charge-state distributions and energy-loss measurements of uranium ions in gases and solids at incident energies of 60.2 and 200MeV/u were performed with the magnetic spectrometer FRS at GSI Darmstadt. The charge distribution was investigated in various gases and solids. We observed a gas–solid effect in ionization and mean charge. This effect arises from the shorter collision time in solids comparable with the lifetimes of the excited states of the projectile. Simultaneously, the stopping force was measured for the same targets. [Copyright &y& Elsevier]

Abstract: An ion-catcher device consisting of a buffer-gas stopping cell and a radio-frequency quadrupole (RFQ) has been built for the SHIPTRAP facility at GSI. Results of characterisation measurements with the buffer-gas cell and the extraction RFQ performed at GSI in Darmstadt and at the MLL (Maier-Leibnitz-Laboratory) in Garching are presented. The set-up was tested off-line using laser-produced ions and on-line using stable beams and fusion–evaporation products. During the on-line measurements the ions with total energies of around 200keV/u were thermalised in helium buffer gas at 40–60mbar. In the following they were guided by a combination of electric RF- and DC-fields until they were transported by the gas flow through the extraction nozzle. After being extracted by a supersonic gas jet the ions were separated from the buffer gas and guided by the extraction RFQ towards subsequent detection systems. Depending on the electric-field strength average extraction times of around 10ms and an overall efficiency (including stopping and extraction) between 4% and 8% have been achieved. [Copyright &y& Elsevier]

We present direct mass measurements of the short-lived 44V, 48Mn, 41Ti and 45Cr nuclei. A novel experimental method has been used that is based on projectile fragmentation, in-flight separation of relativistic heavy ions with the fragment separator (FRS), and on isochronous operation of the experimental storage ring (ESR). A mass resolving power of 110 000 (FWHM) and an accuracy of about (100–500) keV has been achieved. The impact of the present results on the rp-process in X-ray burst models is discussed. [Copyright &y& Elsevier]

An experiment addressing electron capture (EC) decay of hydrogen-like Pm 60 + 142 ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126 (7) s − 1 for automatic analysis and 0.0141 (7) s − 1 for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4). [ABSTRACT FROM AUTHOR]