| 1. |
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Overview of the JET results
- 2015
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 55:10
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Journal article (peer-reviewed)
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| 2. |
- Abel, I, et al.
(author)
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Overview of the JET results with the ITER-like wall
- 2013
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Journal article (peer-reviewed)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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| 3. |
- Romanelli, F, et al.
(author)
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Overview of the JET results
- 2011
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Journal article (peer-reviewed)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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| 4. |
- Ongena, J., et al.
(author)
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Recent progress on JET towards the ITER reference mode of operation at high density
- 2001
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In: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 43, s. A11-A30
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Journal article (peer-reviewed)abstract
- Recent progress towards obtaining high density and high confinement in JET as required for the ITER reference scenario at Q = 10 is summarized. Plasmas with simultaneous confinement H-98(y.2) = 1 and densities up to n/n(Gw) similar to 1 are now routinely obtained. This has been possible (i) by using plasmas at high (delta similar to 0.5) and medium (delta similar to 0.3-0.4) triangularity with sufficient heating power to maintain Type I ELMs, (ii) with impurity seeded plasmas at high (delta similar to 0.5) and low (delta less than or equal to 0.2) triangularity, (iii) with an optimized pellet injection sequence, maintaining the energy confinement and raising the density, and (iv) by carefully tuning the gas puff rate leading to plasmas with peaked density profiles and good confinement at long time scales. These high performance discharges exhibit Type I ELMs, with a new and more favourable behaviour observed at high densities, requiring further studies. Techniques for a possible mitigation of these ELMs are discussed, and first promising results are obtained with impurity seeding in discharges at high triangularity. Scaling studies using the new data of this year show a strong dependence of confinement on upper triangularity, density and proximity to the Greenwald limit. Observed MHD instabilities and methods to avoid these in high density and high confinement plasmas are discussed.
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| 5. |
- Cogordan, JA, et al.
(author)
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Relativistic calculation of 2p53s, 3p and 3d energy levels and transition wavelengths in Ti XIII, Fe XVII and some other neon-like ions
- 1985
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In: Physica Scripta. - 0031-8949. ; 31:6, s. 545-550
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Journal article (peer-reviewed)abstract
- Average energies for the configurations 2p5 3s, 3p and 3d in a number of neon-like ions from Al IV to Xe XLV have been calculated by means of the MCDF computer code of Grant et al. The results have been compared with observations and previous non-relativistic calculations. Fine- structure levels and 3s-3p and ip-3d transition wavelengths have also been calculated with the MCDF code for Ti XIII and Fe XVII, both in the single-configuration approximation and in a multiconfiguration treatment including 2s 2p6 nl. The configuration interaction was found to affect 2p5 3p3S1 most seriously. A separate optimization for the 3p1S0 state was needed, due to the particular radial dependence of this state. The calculated wavelengths show excellent agreement with the observations, and the MCDF calculations are well suited for wavelength predictions in neon-like n = 3 systems
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| 6. |
- Ekberg, JO, et al.
(author)
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Accurate experimental lifetimes of excited levels in sodiumlike sulfur, S VI
- 1983
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 27:6, s. 425-425
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Journal article (peer-reviewed)abstract
- The lifetimes of the terms 3p2P, 3d2D, 4s2S, 4p2P, 4d2D, 4f2F, 5g2G, 6g2G, 6h2H, 7h2H, 7i2I and 8k2K in sodiumlike sulfur, S VI, have been determined using the beam-foil excitation technique. Most of the decay curves were analyzed by means of the ANDC method which corrects for cascading in a very detailed way. Accurate results were thereby obtained which show that an excellent agreement exists between experimental and theoretical values. Some previously noted disagreements between the results of beam-foil experiments and theoretical investigations are explained as being due to less accurate analyses of the experimental data.
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| 7. |
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| 8. |
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| 9. |
- Engström, Lars, et al.
(author)
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Observation of an intensity anomaly in the 3s23p 2P1/2, 3/2-3s3p22S1/2 and 2P1/2 resonance transitions in the Al I isoelectronic sequence
- 1989
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 39:1, s. 66-69
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Journal article (peer-reviewed)abstract
- The intensity ratio of the two fine structure components in the 3s23p 2PJ–3s3p 2S1/2 and 2P1/2 resonance transitions has been measured in Al-like S IV, Cl V, Ar VI and Ti X, using the beam-foil technique. Unexpectedly large deviations from the LS ratios are found, particularly in the 2P–2S case. Although these deviations can be understood qualitatively from theoretical calculations (also reported), large quantitative discrepancies are observed in the beginning of the sequence.
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| 10. |
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