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The root mean square radii of the proton density distribution in ^{16-24}O derived from measurements of charge changing cross sections with a carbon target at ∼900A  MeV together with the matter radii portray thick neutron skin for ^{22-24}O despite ^{22,24}O being doubly magic. Imprints of the shell closures at N=14 and 16 are reflected in local minima of their proton radii that provide evidence for the tensor interaction causing them. The radii agree with ab initio calculations employing the chiral NNLO_{sat} interaction, though skin thickness predictions are challenged. Shell model predictions agree well with the data.

It is well known that the enhancement of halo neutron removal cross sections in neutron halo nuclei. This is one of the evidence for the neutron halo structure. Because the valence neutron of the isomeric state in 16 N is considered to be mainly occupying in the s-orbital, we studied the nuclear structure of 16 N as a candidate for neutron halo nucleus. In this study, we measured one-neutron removal cross sections σ - 1 n using secondary beams of 16 N with a mixture of ground and isomeric states. We used two types of primary beams, 15 N and 18 O, to produce 16 N beams with different isomeric ratios (8.7, 24.2a 16 N beam with a large isomeric ratio is large compared to that obtained with another beam with a small isomeric state. This result suggests that the 16 N isomeric state is considered to have a neutron-halo-like structure. [ABSTRACT FROM AUTHOR]

Abstract: Interaction cross sections () for Ne isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN. The for 27–32Ne in every case exceed the systematic mass-number dependence of for stable nuclei, which can be explained by considering the nuclear deformation. In particular the for 29Ne and 31Ne are significantly greater than those of their neighboring nuclides. These enhancements of for 29Ne and 31Ne cannot be explained by a single-particle model calculation under the assumption that the valence neutron of 29Ne (31Ne) occupies the () orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of 29Ne and s- or p-orbital halo in 31Ne. [Copyright &y& Elsevier]

The interaction cross-sections (σI) of neutron-rich Na isotopes, 23-35Na, on C target have been measured at 250A MeV using the RI beam factory (RIBF) at RIKEN. Mass dependence of σI for 27-35Na suggests monotonic growth of the skin thickness. The root-mean-square nuclear matter radii (r̃m) of 23-35Na were deduced from observed σI via a Glauber-type calculation. These r̃m are in a good agreement with the theoretical prediction by relativistic mean field model (RMF). r̃m of 33-35Na were determined for the first time. [ABSTRACT FROM AUTHOR]

This article describes a diagnostic for measuring neutron emission profile in JT-60U. The Stilbene neutron detector, developed by TRINITI laboratory in Russia, has been installed on the JT-60U Tokamak to measure the neutron emission profile for the first time. The Stilbene neutron detector is a detector which combines a Stilbene crystal scintillator with a neutron-gamma pulse shape discrimination circuit, with a very compact size. Performance tests were carried out using neutron and gamma-ray source prior to installation on JT-60U. Good gamma suppression of the Stilbene neutron detector was verified. Though the neutron emission profile obtained by Stilbene neutron detectors has error of 30% in innermost channel with a calculation using measured plasma parameters, there is an agreement within 10% error in the other channels. [ABSTRACT FROM AUTHOR]

A natural diamond detector (NDD) has been installed on the JT-60U tokamak to measure the flux and the energy distribution of charge exchange (CX) fast neutral particles. A NDD has many important advantages to be used as a CX neutral particle analyzer, for example very compact size, high energy resolution, and high radiation hardness etc., while the neutrons and γ rays are a large noise source in the deuterium plasma. The shield was set up around the NDD to reduce those noises. Time-resolved energy distribution of CX neutral particles corresponding to injected beam energy have been successfully obtained under high intensity neutron yield Yn>1015 n/s. Further enhanced neutral particle fluxes during sawtooth oscillation and Alfvén eigenmodes were observed with the NDD. The performance of the NDD as CX neutral particle spectrometer under high intensity neutron yield was demonstrated for the first time on JT-60U in this work. [ABSTRACT FROM AUTHOR]

17Ne is one of the candidates for proton halo nuclei. To study the halo structure of 17Ne, we measured the reaction cross-sections ( σ{}R) and deduced the density distribution of 17Ne through the energy dependence of σ{}R. From the deduced density, it is found that 17Ne has a long density tail which is consistent with the picture of two valence protons of 17Ne occupying the 2 s1/2 orbital. [ABSTRACT FROM AUTHOR]

Abstract: Interaction cross sections () for neutron-rich Ne isotopes, 28–32Ne on C target have been measured at 240A MeV using the RIBF at RIKEN. A large enhancement of beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes, particularly for 31Ne. The possible halo structure for 29,31Ne which would be caused by the lowering of the pf-shell and nuclear deformation of Ne isotopes are discussed by the preliminary analysis. [Copyright &y& Elsevier]

We report on the first detailed study of intruder configurations in the ground state of 30 Ne by means of the 12 C( 30 Ne,  29 Ne+ γ )X one-neutron knockout reaction at 228 MeV/nucleon. Using a combined analysis of individual parallel momentum distributions and partial cross sections we find: (a) comparable p - and d -wave removal strength to 29 Ne final states with excitation energies below 200 keV, and (b) significant p -wave removal strength to the 620 keV state of 29 Ne, and (c) no evidence for f -wave intruder strength leading to bound 29 Ne final states. The SDPF-U-MIX shell model calculation in the s d – p f model space provides a better overall agreement with the measured energy levels of 29 Ne and the fp -intruder amplitudes in 30 Ne than the SDPF-M prediction, suggesting that the refinement of the s d – p f cross shell interaction and extension of the model space to include the 2 p 1 / 2 and 1 f 5 / 2 levels are important for understanding the island of inversion. [ABSTRACT FROM AUTHOR]

We analyze recently measured total reaction cross sections for 24-38 Mg isotopes incident on 12C targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics (AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of 24-38Mg are then deduced from the measured reaction cross sections by fine tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for 24-36Mg, but still considerably underestimate them for 37,38Mg. The large matter radii suggest that 37,38Mg are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of deformation parameter is predicted by AMD. Large deformation is seen from 31Mg with N = 19 to a drip-line nucleus 40Mg with N = 28, indicating that both the N = 20 and 28 magicities disappear. N dependence of neutron skin thickness is also predicted by AMD. [ABSTRACT FROM AUTHOR]

Neutron-rich N=22, 24, 26 magnesium isotopes were studied via in-beam γ-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory following secondary fragmentation reactions on a carbon target at ≈200 MeV/nucleon. In the one- and two-proton removal channels from 39Al and 40Si beams, two distinct γ-ray transitions were observed in 38Mg, while in the one-proton removal reaction from 37Al a new transition was observed in addition to the known 21+→0g.s.+ decay. From the experimental systematics and comparison to theoretical predictions it is concluded that the transitions belong to the 21+→0g.s.+ and 41+→21+ decays in 36Mg and 38Mg, respectively. For 34Mg, previously reported 21+ and 41+ level energies were remeasured. The deduced E(41+)/E(21+) ratios for 34,36,38Mg of 3.14(5), 3.07(5), and 3.07(5) are almost identical and suggest the emergence of a large area of deformation extending from the N=20 to the N=28 shell quenching. [ABSTRACT FROM AUTHOR]

The two odd-even fluorine isotopes 27,29F were studied via in-beam γ-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. A secondary beam of 30Ne was used to induce one-proton and one-proton-two-neutron removal reactions on carbon and polyethylene targets at midtarget energies of 228 MeV/u. Excited states were observed at 915(12) keV for 27F and at 1080(18) keV for 29F. Both were assigned a 1/21+ spin and parity. The low transition energy for 29F largely disagrees with shell model predictions restricted to the sd model space. Calculations using effective interactions that include the neutron pƒ shell indicate that the N = 20 gap is quenched for 29F, thus extending the "island of inversion" to isotopes with proton number Z = 9. Variations of the N = 20 gap further reveal a strong correlation to the 1/21+ level energy in 29F and suggest a persistent reduced neutron gap for 28O. [ABSTRACT FROM AUTHOR]