| 1. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 2. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 3. |
- Beausang, C W, et al.
(författare)
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Lifetimes of yrast and excited superdeformed states in Gd-150 : effect of particle-hole excitations on the deformation
- 1998
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 417:1-2, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- The quadrupole moments and deformations have been measured for six superdeformed bands in Gd-150. The results indicate evidence for deformation driving properties of both the high-hi intruder and also low-N natural parity states at the superdeformed Fermi surface. Several new transitions have been identified and placed in the low spin non-yrast portion of one of the SD bands.
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| 4. |
- Grahn, T., et al.
(författare)
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Collectivity and configuration mixing in Pb186,188 and Po194
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:6
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of prolate intruder states in Pb186 and oblate intruder states in Po194 have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in Pb188 up to the 8+ state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters |β2|=0.29(5) and |β2|=0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes.
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| 5. |
- Werner, V., et al.
(författare)
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Lifetime and magnetic moment measurements
- 2012
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 366:1, s. Art. no. 012048-
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Konferensbidrag (refereegranskat)abstract
- The g-Plunger technique has been introduced, which allows for the simultaneous measurement of lifetimes and absolute values of g-factors using a plunger device in inverse kinematics. Experiments on the 104,106,108Pd isotopes using Coulomb excitation resulted in g-factors in agreement with literature data. Lifetimes of 2 1 + states have in part significantly changed in this work.
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| 6. |
- Jeppesen, H. B., et al.
(författare)
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Multi-quasiparticle states in (256)Rf
- 2009
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 79:3, s. 031303-
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in (256)Rf were populated via the Pb-208(Ti-50,2n) fusion-evaporation reaction. Delayed gamma-ray and electron decay spectroscopy was performed and three isomeric states in (256)Rf have been identified. A fourth low-energy nonyrast state was identified from the gamma-ray decay of one of the higher lying isomers. The states are interpreted as multi-quasiparticle excitations.
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