The physics program at the super-conducting fragment separator (Super-FRS) at FAIR, being operated in a multiple-stage, high-resolution spectrometer mode, is discussed. The Super-FRS will produce, ...separate and transport radioactive beams at high energies up to 1.5 AGeV, and it can be also used as a stand-alone experimental device together with ancillary detectors. Various combinations of the magnetic sections of the Super-FRS can be operated in dispersive, achromatic or dispersion-matched spectrometer ion-optical modes, which allow measurements of momentum distributions of secondary-reaction products with high resolution and precision. A number of unique experiments in atomic, nuclear and hadron physics are suggested with the Super-FRS as a stand-alone device, in particular searches for new isotopes, studies of hypernuclei, delta-resonances in exotic nuclei and spectroscopy of atoms characterized by bound mesons. Rare decay modes like multiple-proton or neutron emission and the nuclear tensor force observed in high-momentum regime can be also addressed. The in-flight radioactivity measurements as well as fusion, transfer and deep-inelastic reaction mechanisms with the slowed-down and energy-bunched fragment beams are proposed for the high-resolution and energy buncher modes at the Super-FRS.
The Gamow–Teller strength distributions of
116
Sb
and
122
Sb
were measured with the
116
,
122
Sn
(
3
He
,
t
)
116
,
122
Sb
charge-exchange reactions at
140
MeV/u
. The measurements were carried out ...at the Research Center for Nuclear Physics (RCNP) at Osaka University in Osaka, Japan using the Grand Raiden spectrometer. The data were analysed by Multipole-Decomposition Analysis (MDA). The Gamow–Teller strengths summed up to
28
MeV
are
(
38
±
7
)
%
and
(
48
±
6
)
%
of the Ikeda sum rule for
116
Sb
and
122
Sb
, respectively, if the quasi-free scattering (QFS) contribution is not subtracted. These percentages are
(
29
±
7
)
%
and
(
35
±
5
)
%
, respectively, if the QFS contribution is maximally subtracted. These results were compared to those from previous measurements of the same isotopes, to recent measurements of
150
Pm
, and to a Quasi-particle Random-Phase Approximation (QRPA) calculation with Quasi-Particle Vibration Coupling (QPVC). The data suggest that the true QFS contribution is small for
116
Sb
, but are inconclusive about whether the QFS contribution is small or significant for
122
Sb
. Therefore, these data may provide an interesting test for the general quenching phenomenon of the Gamow–Teller Resonance (GTR). However, more research to reveal the nature of the QFS contribution is still needed on both the experimental and the theoretical side.
We present first preliminary results of a novel method for measuring independent isotopic fission yields (IIFYs) of spontaneous fission (SF) via direct mass measurements, at the FRS Ion Catcher ...(FRS-IC) at GSI. Fission products were generated from a 252Cf source installed in a cryogenic stopping cell, and were identified and counted with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS-IC, utilizing well-established measurement and data analysis methods. The MR-TOF-MS resolves isobars unambiguously, even with limited statistics, and its non-scanning nature ensures minimal relative systematic uncertainties amongst fission products. The analysis for extracting IIFYs includes isotope-dependent efficiency corrections for all components of the FRS-IC. In particular, we applied a self-consistent technique that takes into account the element-dependent survival efficiencies in the CSC, due to chemical reactions with the buffer gas. Our IIFY results, which cover several tens of fission products in the less-accessible high-mass peak (Z = 56 to 63) down to fission yields at the level of 10−5, are generally similar to those of the nuclear database ENDF/B-VII.0. Nevertheless, they reveal some structures that are not observed in the database smooth trends. These are the first results of a planned campaign to investigate IIFY distributions of spontaneous fission at the FRS-IC. Upcoming experiments will extend our results to wider Z and N ranges, lower fission yields, and other spontaneously-fissioning actinides.
An inelastic
α
-scattering experiment on the unstable
N
=
Z
, doubly-magic
56
Ni nucleus was performed in inverse kinematics at an incident energy of 50 A.MeV at GANIL. High multiplicity for
α
...-particle emission was observed within the limited phase-space of the experimental setup. This observation cannot be explained by means of the statistical-decay model. The ideal classical gas model at
kT
= 0.4 MeV reproduces fairly well the experimental momentum distribution and the observed multiplicity of
α
particles corresponds to an excitation energy around 96 MeV. The method of distributed
m
α
-decay ensembles is in agreement with the experimental results if we assume that the
α
-gas state in
56
Ni exists at around
113
-
17
+
15
MeV. These results suggest that there may exist an exotic state consisting of many
α
particles at the excitation energy of
113
-
17
+
15
MeV.
We report on the first (p,p′γ) experiments at Ep=80 MeV to investigate the Pygmy Dipole Resonance (PDR) in the semi-magic nucleus 140Ce. This experiment is the latest in a series of experiments to ...investigate the PDR with different complementary probes to provide a multi-messenger data set on the properties of the PDR in 140Ce. In addition, calculations within the Quasi-particle Phonon Model (QPM) have been performed. Cross sections have been calculated for proton- as well as α-scattering reactions based on the transition densities obtained from the QPM, not only at the RPA level, but including the full model space of up to 3p–3h configurations. This allows for the first time to compare the calculations to the experimental results on an absolute scale for single excitations. Agreement between QPM and experiment is observed, which proves the high accuracy of the calculated transition densities for individual PDR states.
A new technique developed for measuring nuclear reactions at low momentum transfer with stored beams in inverse kinematics was successfully used to study isoscalar giant resonances. The experiment ...was carried out at the experimental heavy-ion storage ring (ESR) at the GSI facility using a stored 58Ni beam at 100 MeV/u and an internal helium gas-jet target. In these measurements, inelastically scattered α-recoils at very forward center-of-mass angles (θcm≤1.5°) were detected with a dedicated setup, including ultra-high vacuum compatible detectors. Experimental results indicate a dominant contribution of the isoscalar giant monopole resonance at this very forward angular range. It was found that the monopole contribution exhausts 79−11+12% of the energy-weighted sum rule (EWSR), which agrees with measurements performed in normal kinematics. This opens up the opportunity to investigate the giant resonances in a large domain of unstable and exotic nuclei in the near future. It is a fundamental milestone towards new nuclear reaction studies with stored ion beams.
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
3
Λ
H, 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 2
A
GeV 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.
A rich set of differential cross section of the three-body
2
H(
d
,
dp
)
n
breakup reaction at 160 MeV deuteron beam energy has been measured over a large range of the available phase space. The ...experiment was performed at KVI in Groningen, the Netherlands, using the BINA detector. The cross-section data for the breakup reaction have been normalized to the simultaneously measured
2
H(
d
,
d
)
2
H elastic scattering cross section. The breakup cross sections obtained for 147 kinematically complete configurations near the quasi-free scattering kinematics are compared to the recent approximate calculations for the three-cluster breakup in deuteron–deuteron collisions. The cross sections for 294 kinematic configurations of the quasi-free scattering regime, for which no theoretical calculations exist, are also presented. Besides the three-body breakup, semi-inclusive energy distributions for the four-body
2
H(
d
,
pp
)
nn
breakup are reported.
The experimental data collected during the S515 experiment performed by the R
3
B 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.
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