| 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. |
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| 3. |
- Anderson, Johan, 1973, et al.
(författare)
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Effects of cross-sectional elongation on the resistive edge modes
- 2001
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 8, s. 180-
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Tidskriftsartikel (refereegranskat)abstract
- Resistive edge modes in a shifted noncircular tokamak geometry are investigated in the electrostatic limit. The reduced Braghinskii equations are used as a model for the electrons and an advanced fluid model for the ions. An eigenvalue problem is derived from these equations which is solved numerically. It is found that the resistive ballooning modes are stabilized by plasma elongation forpeaked density profiles. In addition, it is found that the resistive ITG mode may be either stabilized or destabilized by elongation depending on the collision frequency.
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| 4. |
- Anderson, Johan, 1973, et al.
(författare)
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Effects of non-circular tokamak geometry on ion-temperature-gradient driven modes
- 2000
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Ingår i: Plasma Phys. Contr. Fusion. - : IOP Publishing. ; 42, s. 545-
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Tidskriftsartikel (refereegranskat)abstract
- The influence of plasma elongation and Shafranov shift on the stability of electrostatic ion-temperature-gradient driven modes (ηi-modes) is investigated. An advanced fluid model is used for the ions together with Boltzmann distributed electrons. The derived eigenvalue equation is solved both analytically, in the strong ballooning limit, and numerically. It is found that the effects of elongation change from stabilizing, for peaked density profiles, to destabilizing in the flat density regime. In addition, it is shown that the maximum growth rate is shifted towardsshorter wavelengths as the elongation increases. The effects of shaping on tokamak stability are exemplified with data from a Joint European Torus (JET) high-performance mode discharge.
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| 5. |
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| 6. |
- Anderson, Johan, 1973, et al.
(författare)
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Zonal flow generation in ITG turbulence
- 2002
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 9, s. 4500-
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Tidskriftsartikel (refereegranskat)abstract
- In the present work the zonal flow (ZF) growth rate in toroidal ion-temperature-gradient (ITG) mode turbulence including the effects of elongation is studied analytically. The scaling of the ZF growth with plasma parameters is examined for typical tokamak parameter values. The physical model used for the toroidal ITG driven mode is based on the ion continuity and ion temperature equations whereas the ZF evolution is described by the vorticity equation. The results indicate that a large ZFgrowth is found close to marginal stability and for peaked density profiles and these effects may be enhanced by elongation.
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