Search

High-resolution experiments with stored and cooled exotic nuclei have been pioneered and applied with the FRS-ESR facilities at GSI since 1991. Exotic nuclei have been produced, spatially separated in flight with the FRS and injected in the longitudinal dispersive storage ring ESR for high-resolution mass and lifetime measurements. For very short-lived nuclei, i.e., with lifetimes shorter than the cooling time, the ion-optical system of the ring has to be operated in the so-called isochronous mode. Under this condition, the inherent momentum spread of the fragments does not limit the accuracy of experiments if both the revolution time and the magnetic rigidity are simultaneously measured for the circulating ions. In this contribution, we demonstrate a novel feature for the ESR operated in the isochronous mode and the phase-space matching of FRS and ESR. [ABSTRACT FROM AUTHOR]

The FRagment Separator FRS at GSI is a versatile spectrometer and separator for experiments with relativistic in-flight separated short-lived exotic beams. One branch of the FRS is connected to the target hall where the bio-medical cave (Cave M) is located. Recently a joint activity between the experimental groups of the FRS and the biophysics at the GSI and Department of physics at LMU was started to perform biomedical experiments relevant for hadron therapy with positron emitting carbon and oxygen beams. This paper presents the new ion-optical mode and commissioning results of the FRS-Cave M branch where positron emitting 15O-ions were provided to the medical cave for the first time. An overall conversion efficiency of 2. 9 ± 0. 2 × 1 0 − 4 15O fragments per primary 16O ion accelerated in the synchrotron SIS18 was reached. [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]

We have measured for the first time simultaneously both the mean charge states and stopping powers of (35–280) MeV/u 208Pb ions in gases and solids with an accuracy of 1%. The existence at lower energies and disappearance at higher of density effects in the charge-state distribution and the corresponding stopping power are directly confirmed and comparisons with widely used theories and simulations for heavy ions demonstrate strong deviations of up to 27%. However, an unprecedented prediction power of better than 3% has been achieved for the energy loss when the measured mean charge-states are implemented in the Lindhard-Sørensen theory. Our present benchmark data contribute to an improved understanding of the basic atomic collision processes and to numerous applications in nuclear physics. Extending the GANIL data [1] to higher accuracy and energies, we can now answer at which velocities the Bohr-Lindhard density effect in stopping will vanish. [ABSTRACT FROM AUTHOR]

Abstract: The Super-FRS in-flight fragment separator at FAIR will be used to produce exotic nuclei at relativistic energies. High resolution experiments in ion traps with the separated fragments will be performed after they are slowed-down in matter and quickly extracted from a gas-filled stopping cell. Such experiments require an effective range bunching with a high-resolution magnetic spectrometer in combination with a wedge-shaped degrader at the dispersive focal plane. The ion-optical system of the spectrometer proposed here is rather versatile because it consists of several dipole and quadrupole magnets arranged such to serve as an energy-buncher and also as a large-acceptance spectrometer for the analysis of secondary reaction products. The performance and the experimental potential of such a multi-purpose spectrometer are described. [Copyright &y& Elsevier]

Mass measurements of exotic nuclei is a fast developing field which is essential for basic nuclear physics and a wide range of applications. The method of storage ring mass spectrometry has many advantages: (1) a large amount of nuclides can be simultaneously measured; (2) very short-lived (T1/2 ≳ 50 µs) and very rare species (yields down to single ions) can be accessed; (3) nuclides in several atomic charge states can be investigated; (4) half-life measurements can be performed with time-resolved mass spectrometry. In this contribution we concentrate on some recent achievements and future perspectives of the storage ring mass spectrometry. [ABSTRACT FROM AUTHOR]

Abstract: The and orbital electron-capture decays of stored hydrogen- and helium-like 142Pm ions have been measured. So far, such measurements have been performed with only one nucleus, namely 140Pr. The electron-capture decay constant of hydrogen-like 142Pm60+ ions is about 50% larger than that of helium-like 142Pm59+ ions, which is in excellent agreement with the previous measurements in 140Pr ions and with new theoretical predictions. [Copyright &y& Elsevier]

Abstract: In the Facility for Antiproton and Ion Research (FAIR), which is presently designed at GSI (Darmstadt, Germany) a variety of new short-lived nuclides will be generated with the Super-FRS by using projectile fragmentation or uranium fission. The storage rings for the CR-RESR complex have been designed for efficient cooling and accumulation of antiprotons and cooling and deceleration of rare isotopes beams. A new Collector Ring (CR) is planned to be constructed, where one of the functions is devoted also to mass measurements of very short-lived nuclei when it is tuned to an isochronous mode. The structure of the ring lattice and its ion-optical properties in the isochronous mode are described. Nonlinear ion-optical characteristics and their influence on an achievable mass resolving power in an isochronous mode operation of the CR are discussed. [Copyright &y& Elsevier]

Abstract: Two ion-optical layouts of the focusing system in front of the Super-FRS production target are described. The first option uses dedicated single magnet units adapted for the large range of primary beam parameters. The second one employs magnets designed for other components of FAIR (Super-FRS, SIS100). The latter option is favored for the construction phase. [Copyright &y& Elsevier]

Abstract: The future international facility FAIR (Facility for Antiprotons and Ion Research) will deliver beams of all ions up to uranium with intensities of up to 1012 ions/s. At FAIR it will be possible to perform experiments in different fields of physics. A wide range of ions with energies up to 1.5AGeV will be used for the production of fragments by projectile fragmentation/fission at the in-flight fragment separator, Super-FRS. Rare isotopes of all elements up to uranium will be produced and spatially separated within a few hundred nanoseconds, enabling the study of very short-lived nuclei. The Super-FRS is a large-acceptance device utilizing large-aperture superconducting magnets and employing multiple degrader stages to provide monoisotopic nuclear beams. It serves different experimental branches including a new storage-cooler ring system. Because of high primary beam intensity a challenging design of the target area and the components used in the first dipole stage of the Super-FRS is necessary. These efforts include high-power production targets, beam dumps to catch the remaining primary beam and radiation resistant magnets. In this contribution we present the status of the project. [Copyright &y& Elsevier]

Schottky Mass Spectrometry (SMS) and Isochronous Mass Spectrometry (IMS) have been successfully applied for direct mass measurements of exotic nuclides at FRS-ESR facility at GSI. Both experimental methods are sensitive to single stored ions and can cover very efficiently a large number of nuclides in one run. Presently, more than 1100 masses of different nuclides have been covered by SMS and IMS in several FRS-ESR experiments whereby about 350 of them have been determined for the first time. In this paper, we present the status of our experimental program and use the experimental mass values to test the predictive power of modern mass models. [Copyright &y& Elsevier]

Abstract: A short overview of the status of nuclear resonant coherent excitation (RCE) of relativistic nuclei in aligned crystals is presented. The planned GSI accelerator facility FAIR, which will provide intense relativistic heavy-ion beams, will offer new experimental perspectives to study nuclear RCE. Unique opportunities will arise from the availability of bare ions up to uranium with relativistic energies up to 30GeV/u. Synchrotron accelerators, which allow for fine-tuning of the extraction energy, provide ideal conditions for nuclear RCE experiments. Calculations of electromagnetic excitation cross-sections of projectile nuclei in relativistic collisions with individual target atoms are presented, estimates of the nuclear RCE probability in a crystal, a list of candidate nuclei for nuclear RCE experiments, as well as possible experimental schemes at FAIR. [Copyright &y& Elsevier]

Projectile fragments separated in flight with the FRS have been injected into the storage ring ESR. Operating the ESR in the isochronous mode has enabled high-resolution mass measurements of short-lived isotopes. Already in our pilot experiments the Isochronous Mass Spectrometry (IMS) has provided accurate results for a restricted isotope range in the neighborhood of a selected isotope characterized by the best isochronous condition. In the present experiment this restriction has been overcome by precise external magnetic rigidity determination (1.5·10–4) at the dispersive midplane of the FRS. In this way the mass resolving power for neutron-rich fission fragments covering a large mass-over-charge ratio in one spectrum has been improved by up to one order of magnitude and the accuracy by more than a factor of two. [ABSTRACT FROM AUTHOR]

The FRS-ESR facility at GSI provides one of the most efficient methods for direct mass measurements. In the present experiment, exotic nuclei were produced via fragmentation of 152Sm projectiles in a thick beryllium target at 500-600 MeV/u, separated in-flight with the fragment separator FRS, and injected into the storage-cooler ring ESR. Time-resolved Schottky Mass Spectrometry was applied for mass measurements of stored and electron-cooled bare and few-electron ions. 373 different nuclides were identified by means of the spectra of their revolution frequencies. Masses for 18 nuclides (84Zr, 92Ru, 94Rh, 107,108,110Sb, 111,112,114I, 118Ba, 122,123La, 124Ce, 127Pr, 129Nd, 132Pm, 134Sm, 137Eu) have been determined for the first time. Masses for 111,112I and 113Xe have been obtained via known α-decay energies. The experiment and first results will be presented. [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]

Abstract: A review and recent progress are presented from experiments on masses and lifetimes of bare and few-electron exotic nuclei at GSI. Relativistic rare isotopes produced via projectile fragmentation and fission were separated in flight by the fragment separator FRS and injected into the storage ring ESR. This worldwide unique experimental method gives access to all fragments with half-lives down to the microsecond range. The great research potential is demonstrated by the discovery of new isotopes along with simultaneous mass and lifetime measurements. Single particle decay measurements and the continuous recording of both stored mother and daughter nuclei open up a new era for nuclear spectroscopy. The study of bare and few-electron nuclei has also important astrophysical relevance with respect to the hot stellar conditions where reactions and decay are influenced by the degree of atomic ionization. The future international NUSTAR facility at FAIR consisting of a new large-acceptance in-flight separator (Super-FRS) and a dedicated storage ring system (CR–RESR–NESR) will be an ideal tool to study nuclei with new probes and to investigate the majority of relevant r- and rp-process nuclei which are not in reach with the present-day facilities. [Copyright &y& Elsevier]

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]

Abstract: Masses of 582 neutron-deficient nuclides were measured with time-resolved Schottky mass spectrometry at the FRS-ESR facility at GSI, 117 were used for calibration. The masses of 71 nuclides were obtained for the first time. A typical mass accuracy of 30 μu was achieved. These data have entered the latest atomic mass evaluation. The mass determination of about 140 additional nuclides was possible via known energies (Q-values) of α-, β-, or proton decays. The obtained results are compared with the results of other measurements. [Copyright &y& Elsevier]

Recently, much progress has been made with stored exotic nuclei at relativistic velocities . Fragments of 208Pb and 209Bi projectiles and fission products from 238U ions were produced, separated in flight with the fragment separator FRS, and injected into the storage-cooler ring ESR for precision measurements. 114 new masses of neutron-deficient isotopes in the lead region have been measured with time-resolved Schottky Mass Spectrometry (SMS). A new isospin dependence of the pairing energy was observed due to the improved mass accuracy of typically 1.5×10-7 (30 keV). New masses of short-lived neutron-rich fission fragments have been obtained with Isochronous Mass Spectrometry (IMS). An innovative field of spectroscopy has been opened up with lifetime measurements of stored bare and few-electron fragments after applying both stochastic and electron cooling. [Copyright &y& Elsevier]

A large area on the mass surface of neutron-deficient nuclides (36≤Z≤85) was measured with time-resolved Schottky mass spectrometry at the FRS-ESR facilities. The masses of 114 nuclides were obtained for the first time from which 43 were determined via known decay energies. The improved mass accuracy of 30 keV allowed to study the isospin dependence of nuclear pairing, to precisely locate the one-proton dripline for odd-Z isotopes from Tb to Pa and to make crucial tests of the predictive powers of modern mass models. [Copyright &y& Elsevier]

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]

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 isovector potential parameter (b1) of the s-wave pion–nucleus interaction was deduced to be b1=−0.116+0.015−0.017mπ−1 by using the binding energy and width of the recently observed deeply bound 1s π− state in 205Pb combined with the known 1s states of light pionic atoms. An enhancement of b1 over the free-πN value (&z.sfnc;−0.090&z.sfnc;) is indicated, which may infer that the chiral order parameter (squared pion decay constant, fπ2) is reduced by a factor of 0.78+0.13−0.09 in the nuclear medium of 205Pb where the bound π− is located. The isoscalar part is accounted for as arising mainly from a double-scattering effect, without invoking a large density-quadratic term. [Copyright &y& Elsevier]

A fast and reliable range monitoring method is required to take full advantage of the high linear energy transfer provided by therapeutic ion beams like carbon and oxygen while minimizing damage to healthy tissue due to range uncertainties. Quasi-real-time range monitoring using in-beam positron emission tomography (PET) with therapeutic beams of positron-emitters of carbon and oxygen is a promising approach. The number of implanted ions and the time required for an unambiguous range verification are decisive factors for choosing a candidate isotope. An experimental study was performed at the FRS fragment-separator of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany, to investigate the evolution of positron annihilation activity profiles during the implantation of 14 O and 15 O ion beams in a PMMA phantom. The positron activity profile was imaged by a dual-panel version of a Siemens Biograph mCT PET scanner. Results from a similar experiment using ion beams of carbon positron-emitters 11 C and 10 C performed at the same experimental setup were used for comparison. Owing to their shorter half-lives, the number of implanted ions required for a precise positron annihilation activity peak determination is lower for 10 C compared to 11 C and likewise for 14 O compared to 15 O, but their lower production cross-sections make it difficult to produce them at therapeutically relevant intensities. With a similar production cross-section and a 10 times shorter half-life than 11 C, 15 O provides a faster conclusive positron annihilation activity peak position determination for a lower number of implanted ions compared to 11 C. A figure of merit formulation was developed for the quantitative comparison of therapy-relevant positron-emitting beams in the context of quasi-real-time beam monitoring. In conclusion, this study demonstrates that among the positron emitters of carbon and oxygen, 15 O is the most feasible candidate for quasi-real-time range monitoring by in-beam PET that can be produced at therapeutically relevant intensities. Additionally, this study demonstrated that the in-flight production and separation method can produce beams of therapeutic quality, in terms of purity, energy, and energy spread. [ABSTRACT FROM AUTHOR]

The FRagment Separator FRS at GSI is primarily a powerful in-flight separator for short-lived exotic nuclei based on multiple magnetic rigidity analysis and atomic energy-loss in shaped matter. The versatile ion-optical system of the FRS can also be operated as a high-resolution spectrometer and can be used for precise momentum measurements. Other experiments require high rates of exotic nuclei which is accomplished through thick targets and high optical transmission. Here, two developments are presented: A new mode for high-resolution momentum measurements and a high-transmission mode for exotic isotopes spatially separated and energy bunched with achromatic and monoenergetic degraders. [ABSTRACT FROM AUTHOR]

A novel technique to study bound states of exotic hadrons in subatomic nuclei, such as hypernuclei and mesic nuclei, has been developed by employing the Fragment Separator FRS and the WASA central detector at GSI. Two experiments, S447 for studying light hypernuclei, especially hypertriton and a Λ nn bound state, and S490 for searching for η ' mesic-nuclei, were recently performed. Data analyses are currently in progress, and light charged particles such as protons and π ± are clearly observed and identified in the both experiments. For S447, light nuclear fragments that can also be residual nuclei from decays of hypernuclei of interests have been analysed by the FRS, and a momentum resolution, Δ p / p , of 5 × 1 0 − 4 has been achieved. Further data analyses are to be completed. The WASA-FRS project will be continued and extended with the FRS at FAIR Phase 0, and upgrading of the WASA magnet and detectors is currently in progress. Furthermore, construction of a larger detector system with the Super-FRS at FAIR Phase 1 is also under consideration. [ABSTRACT FROM AUTHOR]

Low-energy investigations on rare ion beams are often limited by the available intensity and purity of the ion species in focus. Here, we present the first application of a technique that combines in-flight production at relativistic energies with subsequent secondary beam storage, accumulation and finally deceleration to the energy of interest. Using the FRS and ESR facilities at GSI, this scheme was pioneered to provide a secondary beam of 118Te 52 + for the measurement of nuclear proton-capture at energies of 6 and 7 MeV/u. The technique provided stored beam intensities of about 1 0 6 ions at high purity and brilliance, representing a major step towards low-energy nuclear physics studies using rare ion beams. [ABSTRACT FROM AUTHOR]

The matter radius of the doubly magic 56 Ni was extracted from a measurement of the differential cross section by employing, for the first time, elastic proton scattering in inverse kinematics with a radioactive beam at E kin = 390.2 MeV/nucleon circulating in a storage ring and passing an internal hydrogen gas-jet target with a revolution frequency of around 2 MHz. The novel experimental scheme is based on UHV-compatible Si detectors operated as active vacuum windows, which were implemented in the ESR storage ring at GSI. A matter radius < r m 2 > 1 / 2 = 3. 74 - 0.06 + 0.03 fm was extracted for the doubly-magic self-conjugate nucleus 56 Ni. [ABSTRACT FROM AUTHOR]

Objective. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable 12C ions, the positron emitters 10,11C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam. Approach. An experiment studying the precision of the measurement of ranges of positron-emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner. Main results. High-quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes 11C and 10C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6 × 107 ions in 4 spills for a total duration of 19.2 s, the PET activity range uncertainty for 10C, 11C and 12C is 0.04 mm, 0.7 mm and 1.3 mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from 11C to 10C than when going from 12C to 11C. The much better precision for 10C is due to its much shorter half-life, which, contrary to the case of 11C, also enables to include the in-spill data in the image formation. Significance. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics. [ABSTRACT FROM AUTHOR]

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]

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]

For the first time, the FRagment Separator (FRS) and the Multiple-Reflection Time-Of-Flight Mass-Spectrometer (MR-TOF-MS) particle identification (PID) systems at GSI have been coupled. This new approach adds to the standard FRS PID an additional unambiguous identification of the fragments and the possibility to identify and count long-lived isomeric states (>ms). For this purpose, single-event timestamp information given by a common clock was used to correlate both systems. Two methods were implemented to improve the signal-to-background ratio by more than a factor 2 in the high resolution mass spectrum obtained with the MR-TOF-MS for the 109In isotope. Moreover, the coupling of the systems allows an improvement in the on-line monitoring of the FRS-Ion Catcher (IC) efficiency and extraction time. In addition, range calculations were implemented in the on-line monitoring; a powerful tool for real-time optimization of stopped beam experiments. [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]

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]

Long-lived isomers in 212Bi have been studied following 238U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of 212Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies. [ABSTRACT FROM AUTHOR]

Abstract: Using the high-resolution performance of the fragment separator FRS at GSI we have discovered 60 new neutron-rich isotopes in the atomic number range of . The new isotopes were unambiguously identified in reactions with a beam impinging on a Be target at 1 GeV/nucleon. The production cross-section for the new isotopes have been measured down to the pico-barn level and compared with predictions of different model calculations. For elements above hafnium fragmentation is the dominant reaction mechanism which creates the new isotopes, whereas fission plays a dominant role for the production of the new isotopes up to thulium. [Copyright &y& Elsevier]

Abstract: Masses of 238U projectile fragments have been measured with time-resolved Schottky Mass Spectrometry (SMS) at the FRS-ESR facility at GSI. The exotic nuclei were created in the production target at the entrance of the fragment separator FRS, spatially separated in flight and injected into the storage-cooler ring ESR at about 70% light velocity. This means the ions were mainly bare or carried only a few electrons, e.g., the population of Li-like ions was below 1% for Pt fragments. Accurate new mass values of 33 neutron-rich, stored exotic nuclei in the element range from platinum to uranium have been obtained for the first time. In total more than 150 nuclides including references with well-known masses have been covered in this large-area SMS measurement. A novel data analysis has been applied which reduces the systematic errors by taking into account the velocity profile of the cooler electrons and the residual ion-optical dispersion in this part of the storage ring. The experiment, the data analysis, and the mass values are presented. The experimental data are compared with theoretical predictions demonstrating systematic deviations of up to 1500 keV from modern mass models. [Copyright &y& Elsevier]

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]

Abstract: 238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models. [ABSTRACT FROM AUTHOR]

Abstract: The core-excited isomer in fully-ionized 133Sb has been directly studied for the first time by applying the novel technique of isochronous mass spectrometry at GSI. The neutron-rich nuclides in high charge states were produced by projectile fission of 411 MeV A 238U ions, separated in flight by the fragment separator (FRS) and stored in the isochronous storage ring (ESR). The measured excitation energy is 4.56(10) MeV. The neutral-atom half-life is known to be 17 μs. This is the shortest-lived isomer measured directly with mass spectrometry techniques. The extended in-flight half-life of the bare ions in the ESR, which is due to the exclusion of the strong internal conversion, demonstrates that there should be another nuclear level above that identified from isomer-decay spectroscopy, in support of shell-model calculations. This measurement opens up a new half-life domain for storage-ring measurements. [Copyright &y& Elsevier]