The nuclear structure of 66Se, nucleus beyond the N=Z line on the proton-rich side of the valley of stability, was investigated by the neutron knock-out reaction 67Se(12C,X)66Se using a 12C target. ...The analysis of the singles spectrum of the γ-rays emitted during the de-excitation of the populated low-lying excited states revealed two previously detected (927(4) keV, 1460(32) keV) and three new (744(6) keV, 1210(17) keV, 1661(23) keV) transitions. The 744-keV, the 1210-keV, and the 1460-keV transitions were found to be in coincidence with the one at 927 keV. The spectrum coincident with the 927-keV transition showed a further possible transition at 299(35) keV, which was obscured by significant atomic background in the singles spectrum. This transition might correspond to a peak previously reported at 273(5) keV that could not be assigned to 66Se unambiguously. Based on a comparison of the experimental data to theoretical calculations, four new excited states are proposed which suggest that 66Se exhibits shape coexistence.
We propose a new lattice Boltzmann numerical scheme for binary-fluid surface interactions. The new scheme combines the existing binary free energy lattice Boltzmann method Swift et al., Phys. Rev. E ...54 (1996) and a new wetting boundary condition for diffuse interface methods in order to eliminate spurious variations in the order parameter at solid surfaces. We use a cubic form for the surface free energy density and also take into account the contribution from free energy in the volume when discretizing the wetting boundary condition. This allows us to eliminate the spurious variation in the order parameter seen in previous implementations. With the new scheme a larger range of equilibrium contact angles are possible to reproduce and capillary intrusion can be simulated at higher accuracy at lower resolution.
► We propose a new lattice Boltzmann scheme for binary-fluid surface interactions. ► A cubic form for the surface free energy density is used. ► The scheme eliminates spurious variations in the order parameter at solid boundaries. ► A large range of equilibrium contact angles can be simulated. ► Capillary intrusion can be simulated with high accuracy at relatively low resolution.
The low-lying level structure of 59V and 61V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for 61V while the neutron knock-out ...reaction provided the data for 59V. Four and five new transitions were determined for 59V and 61V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed γ rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2− and 9/2− levels. The (p,p′) excitation cross sections for 61V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, 61V could not be unambiguously placed on the island of inversion.
MINOS is a new apparatus dedicated to in-beam nuclear structure experiments with low-intensity exotic beams in inverse kinematics at intermediate energies above 150MeV/nucleon. The device is composed ...of a thick liquid-hydrogen target coupled to a compact time projection chamber (TPC) serving as a vertex tracker. Either used for in-beam gamma spectroscopy of bound excited states or invariant-mass spectroscopy of unbound states, MINOS aims at improving the luminosity by a very significant factor compared to standard solid-target material experiments while improving experimental resolutions.
Abstract
The matter radius of the doubly magic
$$^{56}$$
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
$$E_{kin}=390.2$$
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
$$<r_{m}^{2}>^{1/2}=3.74^{+0.03}_{-0.06}$$
<
r
m
2
>
1
/
2
=
3
.
74
-
0.06
+
0.03
fm was extracted for the doubly-magic self-conjugate nucleus
$$^{56}$$
56
Ni.
Neutron-rich $^{88,90,92,94}$ Se isotopes were studied via in-beam $\gamma$-ray spectroscopy after nucleon removal reactions at intermediate energies at the Radioactive Isotope Beam Factory. Based on ...gamma-gamma coincidence analysis, low-lying excitation level schemes are proposed for these nuclei, including the 2$_1^+$, 4$_1^+$ states and 2$_2^+$ states at remarkably low energies. The low-lying 2$_2^+$ states, along with other features, indicate triaxiality in these nuclei. The experimental results are in good overall agreement with self-consistent beyond-mean-field calculations based on the Gogny D1S interaction, which suggests both triaxial degree of freedom and shape coexistence playing important roles in the description of intrinsic deformations in neutron-rich Se isotopes.
The low-lying level structure of 63V was studied for the first time by the inelastic proton scattering and the proton knock-out reaction in inverse kinematics. The comparison of the newly observed ...γ-ray transitions at 696(8) keV and 889(16) keV with our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja interaction established two excited states proposed to be the first 11/2− and 9/2− levels. The (p,p′) excitation cross sections were analyzed by the coupled channel formalism assuming pure quadrupole as well as quadrupole+hexadecapole deformations. This resulted in large deformation parameters placing 63V in the island of inversion located below 68Ni.
Nuclear physics experiments with ion storage rings Litvinov, Yu.A.; Bishop, S.; Blaum, K. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317, Številka:
PART B
Journal Article
Recenzirano
Odprti dostop
•Accurate mass measurements of stored exotic nuclei.•Beta decay of highly-charged ions.•In-ring reactions for nuclear structure and astrophysics.•Dielectronic recombination on radioactive ...ions.•Future storage ring projects.
In the last two decades a number of nuclear structure and astrophysics experiments were performed at heavy-ion storage rings employing unique experimental conditions offered by such machines. Furthermore, building on the experience gained at the two facilities presently in operation, several new storage ring projects were launched worldwide. This contribution is intended to provide a brief review of the fast growing field of nuclear structure and astrophysics research at storage rings.
BigRIPS is a powerful two-stage in-flight separator for the research with exotic nuclei studied in frontier experiments since more than a decade. The ion-optical system is very versatile due to the ...multi-stage structure of BigRIPS combined with the ZeroDegree spectrometer or the Superconducting Ring Cyclotron (SRC). Various optical modes can be flexibly realized according to the purpose of experiments. Two categories of developments are presented here. One is a new operating mode of BigRIPS aiming at higher ion-optical resolving power. BigRIPS itself has a two-stage structure. Spatial isotope separation is made at both the first and second stages. In the standard operating mode of BigRIPS, at the second stage the two spatial separations with energy degraders are subtractive in their resolving powers. Here, we present the additive mode. With the resulting increased spatial separation power, the isotopic background can be substantially reduced. Higher ion-optical resolving powers of the first and second BigRIPS degrader stages are also investigated with the goals to reduce further the background and to yield access to new isotopes of heavier elements. The other development is a dispersion-matched system with BigRIPS for high-resolution spectrometer experiments. The BigRIPS and ZeroDegree spectrometer are presently two independent, coupled achromatic systems. A new dispersion-matched mode of BigRIPS and ZeroDegree will enable novel experiments. For high-resolution spectroscopy experiments with high-intensity light projectiles, SRC and BigRIPS can be operated as a dispersion-matched system. The described different ion-optical developments are a base for a new category of experiments exploring exotic nuclei and mesic atoms. Characteristic future experiments with these new ion-optical developments are exemplified in this report.
A new “separated flow” operating mode has been developed for in-flight proton-decay experiments using the SHARAQ spectrometer. In this mode, the protons and heavy-ion products are separated and ...measured in coincidence at two different focal planes of the SHARAQ. The ion-optical properties of the new mode were studied using a proton beam at 246MeV, and the momentum vector was reconstructed from the parameters measured in the focal plane of the SHARAQ. In the experiment with the (16O, 16F) reaction at a beam energy of 247MeV/u, the outgoing 15O+p produced by the decay of 16F were measured in coincidence with the SHARAQ. High energy resolutions of 100keV (FWHM) and ∼2MeV were achieved for a relative energy of 535keV and a 16F kinetic energy of 3940MeV, respectively. The mode allows a new form of missing-mass spectroscopy using a reaction probe with a particle-decay channel.
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