Impurity-seeded ELMy H-modes in JET, with high density and reduced heat load

Monier‐Garbet, P.; Andrew, P.; Belo, P.; Bonheure, G.; Corre, Y.; Crombé, Kristel; Dumortier, P.; Eich, T.; Felton, R.; Harling, J.; Hogan, J.; Huber, A.; Jachmich, S.; Joffrin, E.; Koslowski, H. R.; Kreter, A.; Maddison, G.; Matthews, G. F.; Messiaen, A.; Nave, M. F. F.; Ongena, J.; Parail, V.; Puiatti, M. E.; Rapp, J.; Sartori, R.; Stöber, J.; Tokar, M. Z.; Unterberg, B.; Valisa, M.; Voitsekhovitch, I.; Hellermann, M. von; Contributors, Jet‐Efda

doi:10.1088/0029-5515/45/11/022

Cited by 43 publications

(43 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this case, some of the already rather small type-III ELM energy loss is dissipated by radiative process at the plasma edge before it reaches the PFCs. On the contrary, when the radiative H-modes are maintained in the type-I ELMy H-mode regimes no significant radiative dissipation of the ELM energy flux takes place [44,45]. The main issue regarding the application of this regime to ITER concerns the degraded pedestal pressure and core plasma confinement which is associated with the type-III ELMy H-mode.…”

Section: Radiative Scenariosmentioning

confidence: 99%

ELM control strategies and tools: status and potential for ITER

et al. 2013

View full text Add to dashboard Cite

Operating ITER in the reference inductive scenario at the design values of I P = 15 MA and Q DT = 10 requires the achievement of good H-mode confinement that relies on the presence of an edge transport barrier whose pedestal pressure height is key to plasma performance. Strong gradients occur at the edge in such conditions that can drive MHD instabilities resulting in Edge Localized Modes (ELMs), which produce a rapid energy loss from the pedestal region to the plasma facing components. Without appropriate control, the heat loads on plasma facing components during ELMs in ITER are expected to become significant for operation in H-mode at I P = 6 -9 MA; operation at higher plasma currents would result in a very reduced life time of the plasma facing components. Currently, several options are being considered for the achievement of the required level of ELM control in ITER; this includes operation in plasma regimes which naturally have no or very small ELMs, decreasing the ELM energy loss by increasing their frequency by a factor of up to 30 and avoidance of ELMs by actively controlling the edge with magnetic perturbations. Small/no ELM regimes obtained by influencing the edge stability (by plasma shaping, rotational shear control, etc.) have shown in present experiments a significant reduction of the ELM heat fluxes compared to type-I ELMs. However, so far they have only been observed under a limited range of pedestal conditions depending on each specific device and their extrapolation to ITER remains uncertain. ELM control by increasing their frequency relies on the controlled triggering of the edge instability leading to the ELM. This has been 2 presently demonstrated with the injection of pellets and with plasma vertical movements; pellets having provided the results more promising for application in ITER conditions. ELM avoidance/suppression takes advantage of the fact that relatively small changes in the pedestal plasma and magnetic field parameters seem to have a large stabilizing effect on large ELMs. Application of edge magnetic field perturbation with non-axisymmetric fields is found to affect transport at the plasma edge and thus prevent the uncontrolled rise of the plasma pressure gradients and the occurrence of type-I ELMs. This paper compiles a brief overview of various ELM control approaches, summarizes their present achievements and briefly discusses the open issues regarding their application in ITER. IntroductionThe main goal of current research in the field of magnetically confined plasmas aiming for power generation by nuclear fusion is to optimize high confinement plasma regimes (Hmode) in order to achieve the maximum plasma energy for a given input heating power P in . Thus, in future fusion devices such as the ITER tokamak, which is expected to produce considerable amounts of fusion power P fus , the gain or amplification factor Q = P fus /P in requires to be maximized as well. High confinement H-mode plasmas are characterized by the existence of an Edge Transport Barrier (ETB) in a ...

show abstract

Section: Radiative Scenariosmentioning

confidence: 99%

ELM control strategies and tools: status and potential for ITER

et al. 2013

View full text Add to dashboard Cite

show abstract

“…This is mainly because of the reduced ELM energy loss from plasma in type-III ELMy H-modes. Radiative dissipation of the ELM power fluxes from the pedestal to the divertor is only marginal for type-I ELMs [8,17] and is only observed for very small ELMs in type-III ELMy H-modes [7]. For instance, on JET the transient heat loads due to type-III ELMs onto the outer divertor target were reduced to 2 kJ m −2 [7].…”

Section: Power Load To the Plasma Facing Componentsmentioning

confidence: 99%

Integrated scenario with type-III ELMy H-mode edge: extrapolation to ITER

Rapp¹,

Corre²,

Andrew³

et al. 2009

Nucl. Fusion

View full text Add to dashboard Cite

One of the most severe problems for fusion reactors is the power load on the plasma facing components. The challenge is to develop operation scenarios, which combine sufficient energy confinement with benign heat loads to the plasma facing components. The radiative type-III ELMy H-mode seems a possible solution for such an integrated ITER scenario. Nitrogen seeded type-III ELMy H-modes for the standard inductive scenario and the high beta stationary hybrid scenario are investigated with respect to their transient and steady-state power fluxes to the divertor, confinement properties, edge operational space, core operational space, plasma purity and MHD behaviour. A large database of highly radiative type-III ELMy H-modes on JET is used for extrapolations to ITER. On this basis the transient heat load should be acceptable for ITER. It was found that the scaling of the confinement time with respect to the ion gyroradius is close to the gyro-Bohm scaling. Scalings with respect to the plasma collisionality suggest that the confinement will be good enough for an ITER scenario at 17 MA with a power amplification factor (Q) of 10 and might be marginally good enough for a Q = 10 scenario at 15 MA. Those extrapolations are supported by simulations with an integrated core/edge model COREDIV. In addition the hybrid scenario with type-III edge localized modes has been proven to have improved edge conditions without any modification of the central plasma current profile, indicating it is compatible with a high beta operation for a steady-state ITER Q = 5 scenario.

show abstract

“…In addition, the signals measured by the lines of sight passing through the core (channel nos [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are increased by almost a factor of 2 on average. This is consistent with the total bulk radiation that is estimated to be P bulk rad ∼ 2 MW without and P bulk rad ∼ 4 MW with type III ELM obtained with N seeding.…”

Section: Plasma Radiationmentioning

confidence: 99%

Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Corre

Joffrin

Monier‐Garbet

et al. 2008

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

The performance of the 'hybrid' H-mode regime (long pulse operation with high neutron fluency) has been extensively investigated in JET during the [2005][2006][2007] experimental campaign up to normalized pressure β N = 3, toroidal magnetic field B t = 1.7 T, with type I ELMs plasma edge conditions. The optimized external current drive sources, self-generated non-inductive bootstrap current and plasma core stability properties provide a good prospect of achieving a high fusion gain at reduced plasma current for long durations in ITER.One of the remaining issues is the erosion of the divertor target plates associated with the type I ELM regime. regime with a normalized pressure β N = 2.6 (P NBI ∼ 20-22 MW) and a thermal confinement factor of H * 98 (y, 2) ∼ 0.83 has been recently successfully developed on JET with nitrogen seeding. This scenario shows good plasma edge condition (compatible with the future ITER-like wall on JET) and moderate MHD activity. In this paper, we report on the experimental development of the scenario (with plasma current I p = 1.7 MA and magnetic field B t = 1.7 T) and the trade-off between heat load reduction at the target plates and global confinement due to nitrogen seeding and type III ELM working conditions.

show abstract

Impurity-seeded ELMy H-modes in JET, with high density and reduced heat load

Cited by 43 publications

References 16 publications

ELM control strategies and tools: status and potential for ITER

ELM control strategies and tools: status and potential for ITER

Integrated scenario with type-III ELMy H-mode edge: extrapolation to ITER

Hybrid H-mode scenario with nitrogen seeding and type III ELMs in JET

Contact Info

Product

Resources

About