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The experimental data collected during the S515 experiment performed by the R3B collaboration at GSI/FAIR represent a great opportunity to investigate nucleon knockout reactions of exotic nuclei in the region of Sn using complete kinematics measurements. These cross sections can be used in the future to investigate the quenching in the knockout of the minority species (neutrons or protons) in nuclei far from stability. Some of the arguments put forward are the underestimation of the knockout of deeply bound nucleons, final state interactions or the role of short-range correlations (SRC). Recently, several works based on inclusive measurements have shown that these SRCs could reduce the single nucleon knockout cross sections by around 50%, depending on the neutron excess (N/Z) of the initial projectile. The S515 data can help us to go further in this investigation because it allows to correlate the knockout cross sections of one, two or more nucleons with the number of protons and neutrons emitted from the target and which can be detected by the CALIFA and NeuLAND detectors, respectively, and perform complete kinematical studies on the nature of the event (SRC, evaporation, emission of clusters, final-state interactions...). Here the results obtained for the charge distribution of reaction residues are presented, which is one of the first steps of the still on-going analysis.

The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state 3ΛH, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2AGeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.

An experiment was performed at GSI with the objective of measuring theβ-intensity distribution in the decay of Hg, Au and Pt isotopes around N=126 using the total absorption gamma-ray spectroscopy technique. The aim is to benchmark theoretical models used to make predictions of half-life and neutron emission probabilities of exotic nuclei involved in the rapid neutron capture process, leading to the synthesis of very heavy elements. This paper presents some experimental details and the current status of the analysis.

Experimental determination of the cross sections of proton capture on radioactive nuclei is extremely difficult. Therefore, it is of substantial interest for the understanding of the production of the p-nuclei. For the first time, a direct measurement of proton-capture cross sections on stored, radioactive ions became possible in an energy range of interest for nuclear astrophysics. The experiment was performed at the Experimental Storage Ring (ESR) at GSI by making use of a sensitive method to measure (p,γ) and (p,n) reactions in inverse kinematics. These reaction channels are of high relevance for the nucleosyn-thesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood. The cross section of the 118Te(p,γ) reaction has been measured at energies of 6 MeV/u and 7 MeV/u. The heavy ions interacted with a hydrogen gas jet target. The radiative recombination process of the fully stripped 118Te ions and electrons from the hydrogen target was used as a luminosity monitor. An overview of the experimental method and preliminary results from the ongoing analysis will be presented.

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]

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 mass of an atom incorporates all its constituents and their interactions (1). The difference between the mass of an atom and the sum of its building blocks (the binding energy) is a manifestation of Einstein's famous relation E = [mc.sup.2]. The binding energy determines the energy available for nuclear reactions and decays (and thus the creation of elements by stellar nucleosynthesis), and holds the key to the fundamental question of how heavy the elements can be. Superheavy elements have been observed in challenging production experiments (2-4), but our present knowledge of the binding energy of these nuclides is based only on the detection of their decay products. The reconstruction from extended decay chains introduces uncertainties that render the interpretation difficult. Here we report direct mass measurements of transuranium nuclides. Located at the farthest tip of the actinide species on the proton number-neutron number diagram, these nuclides represent the gateway to the predicted island of stability. In particular, we have determined the mass values of (252-254) No (atomic number 102) with the Penning trap mass spectrometer SHIPTRAP (5). The uncertainties are of the order of 10 keV/ [c.sup.2] (representing a relative precision of 0.05 p.p.m.), despite minute production rates of less than one atom per second. Our experiments advance direct mass measurements by ten atomic numbers with no loss in accuracy, and provide reliable anchor points en route to the island of stability., Exotic nuclei at the limits of stability exhibit new features not present in stable nuclei and therefore provide deeper insight into the nature of the nuclear interaction. At the limit [...]

The boron-10 based multi-grid detector is being developed as an alternative to helium-3 based neutron detectors. At the European Spallation Source, the detector will be used for time-of-flight neutron spectroscopy at cold to thermal neutron energies. The objective of this work is to investigate fine time- and energy-resolved effects of the Multi-Grid detector, down to a few µeV, while comparing it to the performance of a typical helium-3 tube. Furthermore, it is to characterize differences between the detector technologies in terms of internal scattering, as well as the time reconstruction of ∼ µs short neutron pulses. The data were taken at the Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube were installed at the ESS test beamline, V20. Using a Fermi-chopper, the neutron beam of the reactor was chopped into a few tens of µs wide pulses before reaching the detector, located a few tens of cm downstream. The data of the measurements show an agreement between the derived and calculated neutron detection efficiency curve. The data also provide fine details on the effect of internal scattering, and how it can be reduced. For the first time, the chopper resolution was comparable to the timing resolution of the Multi-Grid detector. This allowed a detailed study of time- and energy resolved effects, as well as a comparison with a typical helium-3 tube. [ABSTRACT FROM AUTHOR]

We plan to conduct an experimental search for η'-mesic nuclei in order to investigate in-medium properties of the η' meson. A 2.5 GeV proton beam is employed to produce η'-mesic 11C nuclei with the 12C(p,d)η' 11C reaction. Simultaneous measurements of the forward ejected deuterons and decay protons from η'-mesic nuclei will allow us to achieve high experimental sensitivity. The experiment will be performed at GSI by making full use of the fragment separator FRS and the WASA detector system. The plan of this proposed experiment is described. [ABSTRACT FROM AUTHOR]

We performed a missing-mass spectroscopy experiment of the 12C(p,d) reaction in order to search for η′-mesic nuclei. Excitation spectrum of 11C around the η′-meson production threshold was successfully obtained with a high-statistical sensitivity and sufficiently good energy resolution. Since no peak structure associated with the formation of η′-mesic nuclei was observed, we set constraints on the formation cross sections of η′-mesic states and on the η′-nucleus interaction. [ABSTRACT FROM AUTHOR]

Isomeric states of the neutron-rich isotope 18973Ta116 were populated via fragmentation of a primary beam of 208Pb ions at 1 GeV/u impinging on a 9Be target at GSI, Darmstadt, Germany. The isotopes of interest were separated, identified and delivered to the DESPEC setup. Two isomers were deduced in 189Ta116 and their lifetimes were measured based on the γ-ray time distributions.

The mass of the η' meson is theoretically expected to be reduced at finite density, which indicates the existence of η'-nucleus bound states. To investigate these states, we perform missing-mass spectroscopy for the (p; d) reaction near the η' production threshold. The overview of the experimental situation is given and the current status is discussed. [ABSTRACT FROM AUTHOR]

Carbon ion beams in the energy range of about 100–450 MeV/u offer excellent conditions for tumour therapy, in particular for the treatment of deep-seated radio-resistant tumours. Their depth-dose distribution is characterized by a low dose in the entrance channel, small lateral beam spread and an elevated biological effectiveness in the Bragg peak region. In comparison to protons the radiation field of heavier ions stopping in tissue is however more complex due to nuclear fragmentation reactions occurring along their stopping path. This results in an attenuation of the primary beam flux and a build-up of lower-Z fragments with longer ranges causing the characteristic dose tail beyond the Bragg peak. In the present work the characteristics of secondary charged particles at various depths of water were investigated experimentally using 12C ion beams of 200 and 400 MeV/u delivered by the heavy-ion synchrotron SIS-18 at GSI Darmstadt. The nuclear charge Zf of secondary fragments was identified by combining energy loss and time-of-flight (TOF) measurements. Energy spectra and yields were recorded at lab angles of 0° – 10° and at seven different water depths corresponding to the entrance channel, the Bragg peak region and the tail of the Bragg curve. [ABSTRACT FROM AUTHOR]

A cryogenic stopping cell (CSC) has been commissioned with 238U projectile fragments produced at 1000 MeV/u. The spatial isotopic separation in flight was performed with the FRS applying a monoenergetic degrader. For the first time, a stopping cell was operated with exotic nuclei at cryogenic temperatures (70 to 100 K). A helium stopping gas density of up to was used, about two times higher than reached before for a stopping cell with RF ion repelling structures. An overall efficiency of up to 15%, a combined ion survival and extraction efficiency of about 50%, and extraction times of 24 ms were achieved for heavy α-decaying uranium fragments. Mass spectrometry with a multiple-reflection time-of-flight mass spectrometer has demonstrated the excellent cleanliness of the CSC. This setup has opened a new field for the spectroscopy of short-lived nuclei. [ABSTRACT FROM AUTHOR]

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]

High-energy 12C ions offer favourable conditions for the treatment of deep-seated local tumours. Several facilities for the heavy ion therapy are planned or under construction, for example the new clinical ion-therapy unit HIT at the Radiological University Clinics in Heidelberg. In order to improve existing treatment planning models, it is essential to evaluate the secondary fragment production and to include these contributions to the therapy dose with higher accuracy. Secondary neutrons are most abundantly produced in the reactions between 12C beams and tissues. The dose contribution to tissues by a neutron is fairly small compared with the projectile and the other charged fragments due to no ionisation and the small reaction cross-sections; however, it distributes in a considerably wider region beyond the bragg-peak because of the strong penetrability. Systematic data on energy spectra and doses of secondary neutrons produced by 12C beams using water targets of different thicknesses for various detection angles have therefore been measured in this study at GSI Darmstadt. [ABSTRACT FROM PUBLISHER]

High-energy beams of 12C ions in the range of 80-430 MeV u−1 delivered by the heavy-ion synchrotron SIS-18 are used for radiotherapy of deep-seated localized tumors at the treatment unit at GSI Darmstadt. In order to improve the physical database, the fragmentation characteristics along the penetration path in tissue were investigated experimentally by using a water phantom as tissue-equivalent absorber. Measurements were performed at specific energies of 200 and 400 MeV u−1 of the incident 12C ions and at six different depths before and behind the Bragg peak. Secondary fragments with nuclear charges Zf = 1–5 were identified by scintillation detectors using ΔE–E and time-of-flight techniques. The preliminary results include energy- and angular distributions, fragment yields, build-up curves and attenuation of the primary carbon projectiles. [ABSTRACT FROM PUBLISHER]

We performed a missing-mass spectroscopy experiment of the 12C(p, d) reaction at 2.5 GeV proton energy in order to search for η′ mesic nuclei. An excitation-energy spectrum of 11C was obtained around the η′ production threshold. As no significant peak structure was observed in the spectrum, upper limits of the formation cross section of η′ mesic nuclei have been determined. Preliminary results of the experiment as well as future prospects are given.

We conduct an experimental project to make spectroscopy of deeply bound pionic atoms systematically over wide range of nuclei. We aim at studying the strong interaction in the low energy region, which has close connection to spontaneous chiral symmetry breaking and its partial restoration in nuclear matter. First experimental results show improved spectral resolution and much better statistical sensitivity than previous experiments. Present status of the experiment is reported.

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]

211 Po ions in the ground and isomeric states were produced via 238 U projectile fragmentation at 1000 MeV/u. The 211 Po ions were spatially separated in flight from the primary beam and other reaction products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions. [ABSTRACT FROM AUTHOR]

An excited metastable nuclear state of 192Os in a hydrogen-like charge state has been studied for the first time. It was populated in projectile fragmentation of a 197Au beam on a 9Be target with the UNILAC-SIS accelerators at GSI. Fragmentation products in the region of interest were passed through the fragment separator and injected into the experimental storage ring (ESR). Cooling of the injected beam particles enabled Schottky mass spectrometry to be performed. Analysis shows the lifetime of the state to be considerably longer than that of the neutral ion [τneut = 8.5(14) s]; this change is attributed to hindrance of internal conversion in hydrogen-like 1920s. Calculations have been performed to estimate the lifetime, and the result has been compared with that measured experimentally. There is good agreement between the expected [τH-like = 13.0(24) s] and measured lifetimes (τrest = 15.1-1.3+1.5 s) from the internal decay of 192mOs. This provides a test for the reliability of the values obtained from internal conversion coefficient calculations in highly ionized systems and is the first measurement of its kind to be performed using the ESR setup. [ABSTRACT FROM AUTHOR]

Storage-ring mass spectrometry was applied to neutron-rich 197Au projectile fragments. Masses of 18l,183Lu, 185,186Hf, 187,188Ta, 191W, and 192,193Re nuclei were measured for the first time. The uncertainty of previously known masses of 189,190W and 195Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei. [ABSTRACT FROM AUTHOR]