| 1. |
- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
- Tanaka, Y. K., et al.
(författare)
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Search for eta '-mesic nuclei using (p,d) reaction with FRS/Super-FRS at GSI/FAIR
- 2020
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1643
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Tidskriftsartikel (refereegranskat)abstract
- We plan a semi-exclusive measurement of the C-12(p,dp) reaction to search for eta'-mesic nuclei, aiming at investigating in-medium properties of the eta'-meson. We employ a 2.5 GeV proton beam impinging on a carbon target to produce eta'-mesic C-11 nuclei via the C-12(p,d)eta'circle times C-11 reaction. Using coincidence measurements of the forward going deuterons, important for missing-mass spectroscopy, and decay protons emitted from the eta'-mesic nuclei for event selection will provide a high experimental sensitivity to observe eta'-mesic nuclei. We will perform the measurements by combining the WASA detector system with the fragment separator FRS at GSI and also with the Super-FRS at FAIR in the future. The plan of the experiments and the present status are reported.
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| 3. |
- Doornenbal, P., et al.
(författare)
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Spectroscopy of 32Ne and the "œIsland of Inversion"
- 2009
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Ingår i: Physical Review Letters. - American Physical Society. - 0031-9007 .- 1079-7114. ; 103:3, s. 032501-1-032501-4
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first spectroscopic study of the N = 22 nucleus 32Ne at the newly completed RIKEN Radioactive Ion Beam Factory. A single γ-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a 226 MeV=u 32Ne beam on a carbon target and proton removal from 33Na at 245 MeV=u. This transition is assigned to the deexcitation of the first Jπ = 2+ state in 32Ne to the 0+ ground state. Interpreted through comparison with state-of-the-art shell-model calculations, the low excitation energy demonstrates that the ‘‘island of inversion’’ extends to at least N = 22 for the Ne isotopes.
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| 4. |
- Kuboki, T.a, et al.
(författare)
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Measurement of interaction cross-sections for neutron-rich Na isotopes
- 2011
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Ingår i: Acta Physica Polonica B. - : Jagellonian University. - 0587-4254 .- 1509-5770. ; 42:3-4, s. 765-768
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Tidskriftsartikel (refereegranskat)abstract
- 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 (rm) of 23-35Na were deduced from observed σI via a Glauber-type calculation. These rm are in a good agreement with the theoretical prediction by relativistic mean field model (RMF). rm of 33-35Na were determined for the first time.
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| 5. |
- Reifarth, R., et al.
(författare)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Konferensbidrag (refereegranskat)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 6. |
- Takechi, M., et al.
(författare)
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Interaction cross sections for Ne isotopes towards the island of inversion and halo structures of 29Ne and 31Ne
- 2012
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Ingår i: Physics Letters B. - Elsevier : Elsevier BV. - 0370-2693 .- 1873-2445. ; 707:3-€“4, s. 357-361
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Tidskriftsartikel (refereegranskat)abstract
- Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of the neutron dripline have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN. The σI for 27–32Ne in every case exceed the systematic mass-number dependence of σI for stable nuclei, which can be explained by considering the nuclear deformation. In particular the σI for 29Ne and 31Ne are significantly greater than those of their neighboring nuclides. These enhancements of σI 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 0d3/2 (0f7/2 ) 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.
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| 7. |
- Ozawa, A., et al.
(författare)
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Charge-changing cross sections of 30Ne, 32,33Na with a proton target
- 2014
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 89, s. 044602-1-044602-5
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Tidskriftsartikel (refereegranskat)abstract
- The total charge-changing, charge pick-up, and partial charge-changing cross sections of very neutron-rich nuclei (30Ne, 32,33Na) with a proton target have been measured at ~240A MeV for the first time. We introduced the phenomenological correction factor in Glauber-model calculations for the total charge-changing cross sections with the proton target, and applied it to deduce the proton radii of these nuclei. For 30Ne and 32Na, the neutron skin thicknesses of the nuclei were deduced by comparing the proton radii with the matter radii deduced from the interaction cross-section measurements. A significant thick neutron-skin has been observed for the nuclei. We also found that the charge pick-up cross sections are much larger than those in the systematics of stable nuclei.
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| 8. |
- Rodriguez-Sanchez, J. L., et al.
(författare)
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Systematic study of Δ (1232) resonance excitations using single isobaric charge-exchange reactions induced by medium-mass projectiles of Sn
- 2022
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Ingår i: Physical Review C. - 2469-9993 .- 2469-9985. ; 106:1
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Tidskriftsartikel (refereegranskat)abstract
- The fragment separator FRS has been used for the first time to measure the (n,p)- and (p,n)-type isobaric charge-exchange cross sections of stable Sn112,124 isotopes accelerated at 1A GeV with an uncertainty of 3% and to separate quasielastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic contribution can be associated to the excitation of isobar Δ(1232) resonances and to the pion emission in s wave, in both the target and projectile nuclei, while the quasielastic contribution is associated with the nuclear spin-isospin response of nucleon-hole excitations. The data lead to interesting results, where we observe a clear quenching of the quasielastic component, and their comparisons to theoretical calculations demonstrate that the baryonic resonances can be excited in the target and projectile nuclei. To go further in this investigation, we propose to study the excitation of baryonic resonances, taking advantage of the combination of high-resolving power magnetic spectrometers with the Wide Angle Shower Apparatus (WASA) calorimeter. These new measurements will allow us to determine the momenta of the ejectiles and pions emitted in coincidence after the single isobaric charge-exchange collisions, providing us unique opportunities to study the evolution of the baryonic resonance dynamics with the neutron-proton asymmetry through the use of exotic radioactive ion beams.
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| 9. |
- Fukuda, M., et al.
(författare)
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Reaction cross section studies at NIRS and RIBF
- 2010
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Ingår i: American Institute of Physics Conference Series. - American Institute of Physics : AIP. ; , s. 270-273
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Konferensbidrag (refereegranskat)abstract
- Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.
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| 10. |
- Grigorenko,, et al.
(författare)
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Deep excursion beyond the proton dripline. II. Toward the limits of existence of nuclear structure
- 2018
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Ingår i: Physical Review C. - 2469-9985 .- 2469-9993. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in Cl-28,Cl-29 and Ar-29,Ar-30 have been theoretically substantiated, and analogous deviations have been predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with Ar-26 and Cl-25 found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and gamma rays following decays of such systems as well as their beta-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of Cl-30 and Ar-31 ground-state studies. Such a synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking) being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.
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