Different excited states of
13
C populated in the
10
B +
10
B reactions at a beam energy of 72.2 MeV were investigated. The study revealed both well-known and new, or infrequently populated states. ...In particular, the inclusive excitation energy spectra showed the presence of most of the states belonging to the K = 3/2
-
rotational band that was proposed by several authors. Furthermore, a possibly new state at E
x
= 19.0 MeV was strongly populated in the
α
+
9
Be coincidences. The measured state was found to have a well defined cluster structure. Additionally, so far unobserved
α
-decay of the two rarely seen high-energy
13
C states at 21.9 and 23.6 MeV is discussed.
We have studied spin observables in the three-body break-up reaction in deuteron–deuteron scattering in the phase-space regime that corresponds to the quasi-free deuteron–proton scattering process ...with the neutron as spectator. The data are compared to measurements of the elastic deuteron–proton scattering process and state-of-the-art Faddeev calculations. The results for iT11 and T22 for the quasi-free scattering data agree very well with previously published elastic-scattering data. A significant discrepancy is found for T20, which could point to a break-down of the quasi-free assumption.
A phoswich array consisting of 60 elements has been built and used in pionic-fusion experiments at the Kernfysisch Versneller Instituut (KVI). The array is used in conjunction with a magnetic ...spectrometer and a time-of-flight system to measure the fragments produced in
3He+
4He and
4He+
6Li reactions at beam energies of 85.3 and 59.1
A
MeV, respectively. The particle identification for
Z
≤
5
has been performed by means of time-of-flight and pulse-shape analysis techniques. A momentum resolution of
∼
1
%
was achieved. The dependence of the integrated light output on ion energy, momentum, and mass has been studied. The detector performance, light response, ion identification, momentum and time calibration, and acceptance of the Heavy-Ion detector array are presented and discussed.
The role of pions in the nuclear interaction has been studied in pionic fusion experiments using the AGOR accelerator facility at KVI. Pionic fusion is a highly coherent process in which two nuclei ...fuse to a united nucleus and the available centre-of-mass (C.M.) energy is emitted through the pion channel. The examined reactions were 4He(3He, π0)7Be and 6Li(4He, π0)10B⁎ and both reactions were performed at C.M. energies about 10 MeV above the coherent pion production threshold. Here, the experimental results for the 6Li(4He, π0)10B⁎ reaction will be presented and discussed. In order to provide sensitivity to the full dynamics and relevant processes involved in the pionic fusion reaction, almost the full angular distribution of neutral pions has been determined. In a phenomenological analysis, the contributions of Legendre polynomials to reproduce the behaviour of the angular distribution have been studied. The results of this analysis confirm the importance of the clustering correlations for the 6Li(4He, π0)10B⁎ reaction. The mass dependence of the pionic fusion reaction is in agreement with the results of the existing models extrapolated to this reaction.
A 2π hemispherical detector consisting of 64 CsI(Tl) scintillator modules covering the angular range of 80°–160° has been constructed. This detector is employed as the Inner Shell of the Plastic Ball ...detector and was used in two experimental programs concerning the study of pionic fusion in light-ion systems. The geometry and construction are presented. The improved response of the combined detectors for photons are discussed. An energy calibration method using high energy cosmic muons for the Inner Shell and the Plastic Ball has been developed and the calibration results are compared to the results of the same method in the Monte-Carlo simulation. The improved acceptance of the combined detectors for the π0 detection in the 6Li(4He, π0)10B* experiment are presented and discussed.
The neutron-rich unbound fluorine isotope ^{30}F_{21} has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasifree proton knockout ...reaction of ^{31}Ne nuclei at 235 MeV/nucleon. The mass and thus one-neutron-separation energy of ^{30}F has been determined to be S_{n}=-472±58(stat)±33(sys) keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in S_{n}(^{30}F) shows that the "magic" N=20 shell gap is not restored close to ^{28}O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron d and fp orbitals, with the 1p_{3/2} and 1p_{1/2} orbitals becoming more bound than the 0f_{7/2} one. This degeneracy and reordering of orbitals has two potential consequences: ^{28}O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both ^{29,31}F appear to be good two-neutron halo-nucleus candidates.The neutron-rich unbound fluorine isotope ^{30}F_{21} has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasifree proton knockout reaction of ^{31}Ne nuclei at 235 MeV/nucleon. The mass and thus one-neutron-separation energy of ^{30}F has been determined to be S_{n}=-472±58(stat)±33(sys) keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in S_{n}(^{30}F) shows that the "magic" N=20 shell gap is not restored close to ^{28}O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron d and fp orbitals, with the 1p_{3/2} and 1p_{1/2} orbitals becoming more bound than the 0f_{7/2} one. This degeneracy and reordering of orbitals has two potential consequences: ^{28}O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both ^{29,31}F appear to be good two-neutron halo-nucleus candidates.
NeuLAND is the neutron detector used by the R3B collaboration, which is part of the NUSTAR collaboration at the FAIR facility. NeuLAND is used for the detection of fast neutrons in the range of 200 ... MeV- 1000 MeV and is composed of plastic scintillators. Neutrons can undergo hadronic scattering with the scintillator material to produce charged particles, which in turn can be detected by their scintillation light. The high granularity of the detector allows for an accurate reconstruction of the primary interaction points of the neutrons. With these interaction points and with the information from the other detectors in the R3B setup, the reaction at the target can be kinematically reconstructed. This reconstruction is the tool that enables the R3B collaboration to study complex reactions. However, particles produced through reactions of the incoming radioactive beam with other R3B detectors may also enter NeuLAND’s active volume and generate a significant background. In this paper, Monte Carlo simulations are utilized to explore possible reduction techniques of this background. In particular, the reduction of the charged-particle component of this background through the use of a VETO wall is explored for the initial setup of the R3B experiment. The list of physics processes considered and their implementation in the simulations are tested against experimental data to ensure that conclusions about the background reduction are meaningful. Extensive simulations show that the use of a VETO wall is, in many situations, not necessary.
Direct proton-knockout reactions of Sc-55 at similar to 220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of Ca-54 were investigated through -ray and ...invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological intemucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the Sc-55 ground state with states in Ca-54. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of Sc-55, valence proton removals populated predominantly the ground state of Ca-54. This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
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