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Nuclear mass is a key property of atomic nuclei. The accurate determination of nuclear masses provides information for the nuclear shell structure and nuclear deformations. The FRS Ion Catcher experimental setup at GSI, Darmstadt was used to perform mass measurements of 252Cf fragments using a multiple-reflection time-of-flight mass spectrometer. The reported results are compared to previous measurements and their implication in the estimation of two-neutron separation energy is discussed. [ABSTRACT FROM AUTHOR]

The future Super-FRS separator-spectrometer at FAIR will provide rare-isotope beams for key experiments in nuclear structure, astrophysics and nuclear reactions. The Super-FRS will use large-aperture magnets, which is important for the acceptance of nuclear reaction products with a large transverse and longitudinal emittance. In the standard ion-optical separator mode, magnetic rigidity analysis in combination with atomic energy-loss will be performed for clean isotopic spatial separation, once in the Pre-Separator and second in the Main-Separator. New ion-optical developments, prepared for different categories of experiments, are presented in this article. The operating modes described in the early publications of the project are updated in the first part of the paper. In the second part, special ion-optical modes mainly for the experiments of the Super-FRS Experiment Collaboration are discussed. This collaboration is the succession of the FRS Collaboration which has concentrated on separator-spectrometer experiments with the present facility at GSI since 1990. [ABSTRACT FROM AUTHOR]

One-neutron knockout reactions have been studied in a systematic way for a set of neutron-rich projectiles. The goal of the experiment, performed at GSI, was to explore the evolution of the nuclear structure close to the neutron drip line, in the region between C and Al. The momentum distributions of the surviving fragments and the cross-sections of the knockout process have been measured and used as physical observables. This report focuses on oxygen and nitrogen isotopes around N = 14. In particular, we discuss the case of 22N, for which the mentioned observables have been determined for the first time. We will consider 23O, already studied in earlier experiments, as a reference. [ABSTRACT FROM AUTHOR]

Precise mass measurements of short-lived exotic nuclei are very important for the understanding of basic nuclear structure physics and astrophysical nucleosynthesis in nature, as well as for the test and the development of theoretical nuclear mass models. At GSI, the Isochronous Mass Spectrometry (IMS) dedicated to mass measurements of short-lived nuclides was developed. In this contribution, the IMS technique is briefly reviewed. Recently, the first large-scale measurement on the 238U fission fragment was done successfully. The measured mass values are in excellent agreement with the recent Penning trap data, however, they show a systematical deviation from the values in the latest atomic mass evaluation. Some representative results from this experiment will be presented, including their impact on nuclear structure physics and astrophysical r-process nucleosynthesis. [ABSTRACT FROM AUTHOR]

Abstract: Rare isotope beams can be efficiently produced at relativistic energies via projectile fragmentation and projectile fission. Magnetic rigidity analysis in combination with atomic energy loss (Bρ–ΔE–Bρ method) in profiled matter placed at dispersive focal planes represents the tool for spatial separation in flight. The next-generation in-flight separators at high energies will consist of multiple degrader stages to provide intense monoisotopic fragment beams of all elements up to uranium. The pre-separator layout with the first degrader system holds many technical challenges, e.g. to handle the high-power primary beams characterized by a large range in time structure, from a DC beam to very short bunches. The latter requirement is particularly necessary for high-intensity primary beams bunched in short pulses (50ns) for experiments with storage-rings. Large acceptance and high-separation power for uranium fission fragments and for exotic nuclei far from stability are the keys to serve the nuclear structure and astrophysical research at the frontiers. Consequently, large aperture magnets have to be applied to handle the inevitable large phase-space volume. The correction of higher-order image aberrations is a challenge and essential to achieve a high-separation power for the Bρ–ΔE–Bρ method. [Copyright &y& Elsevier]

The planned new international accelerator facility FAIR (Facility for Antiproton and Ion Research, [1]) at GSI will provide primary beams of all projectiles up to uranium with energies up to 1.5 GeV/n for nuclear structure physics. The maximum intensities of these projectile beams will be (1–3) 1012/s, leading to a maximum beam power of 58 kW. 10–20% of the primary beam will react in a high-power production target at the entrance of the Super-FRS (Super-conducting Fragment Separator, [2]). The Super-FRS is a large-acceptance two-stage fragment separator which will provide spatially separated isotopic beams of exotic nuclei. The non-reacting primary beam will be dumped at dedicated beam catchers, located at well defined places in the first part of the Super-FRS. The target area as well as the beam dump area is in high fluxes of high-energy particles, mainly neutrons and protons. Since magnetic elements located in these areas have to be reliably operated for the lifetime of the facility (∼20 years) their design has to be radiation resistant. Presently we consider building the magnet coils using MIC (Mineral Insulation Cable) technology. In this paper we present radiation issues, magnet specification, and possible magnetic designs of the first quadrupole magnet placed 1 m downstream of the production target. [ABSTRACT FROM AUTHOR]

The FRS-RISING set-up at GSI uses secondary radioactive beams at relativistic energies for nuclear structure studies. At GSI the fragmentation or fission of stable primary beams up to 238U provide secondary beams with sufficient intensity to perform γ-ray spectroscopy. The RISING set-up is described and results of the first RISING campaign are presented. New experimental methods at relativistic energies are being investigated. Future experiments focus on state-of-the art nuclear structure physics covering exotic nuclei all over the nuclear chart. [ABSTRACT FROM AUTHOR]

The GSI projectile fragment separator FRS has demonstrated with many pioneering experiments the research potential of in-flight separators at relativistic energies. Although the present facility has contributed much to the progress in the field of nuclear structure physics, major improvements are desirable in the future. The characteristics of the proposed next-generation facility at GSI, the Super-FRS, will be presented and compared to other projects. The Super-FRS is a large-acceptance superconducting fragment separator followed by different experimental branches including a combination with a new storage-cooler ring system. This system consists of a collector ring (CR) and a new experimental storage ring (NESR) which allow precision mass and lifetime measurements as well as in-ring reaction studies. The NESR can be operated in combination with an electron ring to measure electron scattering with exotic nuclei. This electron heavy-ion collider will open up new fields for nuclear structure research. [Copyright &y& Elsevier]

The conceptual design of a next-generation cryogenic stopping cell (CSC) for the Low-Energy Branch (LEB) of the Super-FRS has been developed. It builds on advanced techniques implemented in the prototype version of the CSC, which has recently been commissioned as part of the FRS Ion Catcher with 238 U projectile and fission fragments produced at 1000 MeV/u. These techniques include cryogenic operation to ensure a high purity of the stopping gas and high-density operation enabled using an RF carpet with a small electrode structure size. The next generation CSC implements several novel concepts (e.g. perpendicular extraction) which lead to enhanced performance compared to the prototype CSC: (i) extremely short extraction times, (ii) higher rate capability, (iii) increased areal density without deteriorating extraction times, efficiencies or rate capability, (iv) minimized RF power, (v) precise range measurement of the ions and (vii) improved cleanliness of the CSC. [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]

Heavy neutron-rich nuclei were populated via the fragmentation of a E/A = 1 GeV Due to image rights restrictions, multiple equation(s) cannot be graphically displayed. beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed γ rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. The newly discovered isomers are in Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as welt as BCS calculations were performed. [ABSTRACT FROM AUTHOR]

Abstract: The unbound nuclei 9He and 10He have been produced in proton-knockout reactions from a 280 MeV/u 11Li beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, and , employing reaction models incorporating the structure of 11Li. The relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of . This spectrum also shows evidence for resonance states at and at 2.4 MeV above the threshold. It is argued that the s-state might not be the 9He ground state. For , the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at () superimposed on a correlated background, or two overlapping resonances, a ground state at 1.54(11) MeV () together with an excited state at 3.99(26) MeV (). The two possible interpretations are discussed. [Copyright &y& Elsevier]

Abstract: One-neutron knockout reactions of 24–28Ne in a beryllium target have been studied in the Fragment Separator (FRS), at GSI. The results include inclusive one-neutron knockout cross-sections as well as longitudinal-momentum distributions of the knockout fragments. The ground-state structure of the neutron-rich neon isotopes was obtained from an analysis of the measured momentum distributions. The results indicate that the two heaviest isotopes, 27Ne and 28Ne, are dominated by a configuration in which a neutron is coupled to an excited state of the 26Ne and 27Ne core, respectively. [Copyright &y& Elsevier]

Abstract: The first reaction spectroscopy on the ground state structure of 33Mg through the measurement of the longitudinal momentum distribution from the one-neutron removal reaction using a C target at is reported. The experiment was performed at the FRS, GSI. The distribution has a relatively narrow width ( (FWHM)) and the one-neutron removal cross-section is . An increased contribution from the orbital is required to explain the observation showing its lowering compared to existing model predictions. This provides new information regarding the configuration of 33Mg and the island of inversion. [Copyright &y& Elsevier]

Abstract: The previously pioneered Isochronous Mass Spectrometry (IMS) has been extended by an additional precise magnetic-rigidity determination to enable accurate large-scale measurements of stored short-lived relativistic nuclei with the FRS-ESR facility at 382 MeV/u. With this novel experimental tool the mass resolving power and accuracy have been improved by a factor of about 3. The recorded broad-band revolution time spectrum corresponds to the mass-over-charge range of about 6%. A mass resolving power of 200 000 (FWHM) and a typical accuracy of 120 keV have been achieved almost over the entire spectrum. The masses of 35 neutron-rich nuclides have been directly measured in the element range from aluminum to barium. The Masses of 8 nuclides (85,86As, 89Se, 123Ag, 138Te, 140,141I, 143Xe) have been measured for the first time. The results are compared with previous experimental data and theoretical predictions. The evolution of the shell closure towards doubly-magic 78Ni is discussed. [Copyright &y& Elsevier]

Abstract: The first results from the stopped beam RISING experimental campaign performed at the GSI laboratory in Darmstadt, Germany, are presented. RISING (Rare ISotope Investigations at GSI) constitutes a major new experimental program in European nuclear structure physics research aimed at using relativistic energy (typically around 1GeV per nucleon) projectile fragmentation reactions to populate nuclei with highly exotic proton-to-neutron ratios compared to the line of beta stability. In its high-efficiency ‘stopped beam’ configuration, the RISING γ-ray spectrometer consists of 105 individual, large volume germanium crystals which view a focal plane in which the exotic nuclei are brought to rest (i.e. ‘stopped’). Here, decays from metastable or ‘isomeric’ states with half-lives in the nano to milliseconds range can be observed, often providing the first spectroscopic information on these exotic nuclear species. This paper introduces the physics aims of the stopped RISING collaboration and presents some technical details on the RISING detector array. Results of initial commissioning experiments are also shown and details of the planned future experimental program are given. [Copyright &y& Elsevier]

This paper presents the results of experimental investigations of (p,pn), (p,pα) and (p,p 6He) reactions with relativistic 6He and 8He beams impinging on a hydrogen target. Information on the structure of extremely neutron-rich nuclei was obtained by using the unique characteristic of quasi-free scattering processes and inverse kinematics. For the first time, momentum distributions of complex clusters inside 6He and 8He were measured. Spectroscopic factors for valence neutrons, α- and 6He clusters were deduced from the experimental data. They demonstrate that the filling of the p½ shell is the essential feature of the 8He structure. It is shown that the 8He cluster structure can be considered as a 6He core plus two valence neutrons. [Copyright &y& Elsevier]

One-nucleon removal reactions at relativistic energies have been used as a spectroscopic tool to characterise the ground state properties of several neutron-rich isotopes in the sd-shell. Using the FRS at GSI, the longitudinal momentum distributions of the emerging fragments after one-nucleon removal were measured. The relative contributions of the remaining fragments in their ground and excited states have been determined from measurements of γ rays in coincidence with the longitudinal momentum distributions. In particular the breakup of 23O has been investigated. The interpretation of our measurements, in the framework of a simple theoretical model, favours a spin and parity assignment of 1/2+ for the 23O ground state in agreement with shell model predictions. [Copyright &y& Elsevier]