Pedestal Characteristics of H-Mode Plasmas in JT-60U and ASDEX Upgrade

Urano, H.; Kamada, Y.; Takizuka, T.; Suttrop, W.; Horton, L. D.; Lang, P. T.; Kubo, H.; Oyama, N.; Takenaga, H.; Asakura, N.

doi:10.1585/jspf.81.280

Cited by 5 publications

(13 citation statements)

References 29 publications

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“…4. This half reduction of ELM energy loss agrees with experimental observations [4,5]. We also do simulations with a low-field-side (LFS) pellet and obtain similar results.…”

Section: Fig 2 Time Evolution Of Background Total Pressure P Profilsupporting

confidence: 89%

“…The resultant energy loss is less than half of the 'natural' ELMs as shown in figure 5. This reduction of ELM energy loss agrees with experimental observations in ASDEX Upgrade [4,5] and DIII-D [27]. We also performed simulations with a LFS pellet and obtained similar results.…”

Section: Elm Triggered By Pellet Energy Absorptionsupporting

confidence: 87%

“…Multi-machine experiments showed a wide range of phenomena, which follow pellet ablation [1,[3][4][5][6][7]. This includes very prompt ELM onset at the time when the pellet passes the pedestal region [5], ability to trigger the ELM with a high repetition rate by the pellet injected from any location [1], a slight decrease (∼10%) in the electron temperature along the pellet penetration path before the density increase [6] and a magnetic perturbation induced by the pellet observed even in non-ELMing H-mode and L-mode plasmas [3,7].…”

Section: Introductionmentioning

confidence: 99%

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Integrated simulation of ELM triggered by a pellet through energy absorption and transport enhancement

Hayashi¹,

Parail²,

Koechl³

et al. 2011

Nucl. Fusion

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Abstract. Two integrated core / scrape-off-layer (SOL) / divertor transport codes TOPICS-IB and JINTRAC with links to MHD stability codes have been coupled with models of pellet injection to clarify effects of pellet on the behavior of edge localized modes (ELMs). The energy absorption by pellet and its further displacement due to ExB drift as well as transport enhancement by the pellet were found to be able to trigger the ELM. The ablated cloud of pellet absorbs the background plasma energy and causes the radial redistribution of pressure due to the subsequent ExB drift. On the other hand, the sharp increase in local density and temperature gradients in the vicinity of ablated cloud could cause transient enhancement of heat and particle transport. Both mechanisms produce a region of an increased pressure gradient in the background plasma profile within the pedestal, which triggers the ELM. The mechanisms have the potential to explain a wide range of experimental observations.

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“…4. This half reduction of ELM energy loss agrees with experimental observations [4,5]. We also do simulations with a low-field-side (LFS) pellet and obtain similar results.…”

Section: Fig 2 Time Evolution Of Background Total Pressure P Profilsupporting

confidence: 89%

Section: Elm Triggered By Pellet Energy Absorptionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Integrated simulation of ELM triggered by a pellet through energy absorption and transport enhancement

Hayashi¹,

Parail²,

Koechl³

et al. 2011

Nucl. Fusion

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“…The values of τ ELM and ped are typical values in experiments [1,5,8]. On the other hand, the value of χ max ELM is chosen to obtain ELM energy and particle losses comparable to JT-60U experiments [3,8]. The other parameters are chosen as puf = 0.3×10 22 s −1 , f dpump = 0.01, f wpump = 0, f dr = 0.02, L r = 0.4 m and T n = 3 eV.…”

Section: Integrated Simulation Resultsmentioning

confidence: 99%

“…The ELM cycle consists of two phases: an ELM crash by the MHD instability inducing energy and particle losses from the pedestal plasma and a quiescent phase recovering the pedestal pressure between ELMs (inter-ELM phase). A multi-machine analysis shows that the ELM energy loss increases with decreasing collisionality [1][2][3] and the inter-ELM transport increases with collisionality [3,4]. Additionally, recent experiments showed that the toroidal rotation and the toroidal field ripple also affects the ELM energy loss [5].…”

Section: Introductionmentioning

confidence: 99%

Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas

Hayashi¹,

Takizuka²,

Aiba³

et al. 2009

Nucl. Fusion

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The energy loss due to an edge localized mode (ELM) crash and its cycle have been studied by using an integrated core transport code with a stability code for peeling–ballooning modes and a transport model of scrape-off-layer (SOL) and divertor plasmas. The integrated code reproduces a series of ELMs with the following characteristics. The ELM energy loss increases with decreasing collisionality and the ELM frequency increases linearly with the input power, as seen in experiments of type-I ELMs. A transport model with the neoclassical transport in the pedestal connected to the SOL parallel transport reproduces a lowered inter-ELM transport in the case of low collisionality so that the ELM loss power is enhanced as observed in experiments. The inter-ELM energy confinement time evaluated from simulation results agrees with the scaling based on the JT-60U data. The steep pressure gradient in the core just beyond the pedestal top, desirable for improved H-mode plasmas with the H H98y2 factor above unity, is found to enhance the ELM energy loss and reduce the ELM frequency so that the ELM loss power remains constant. The steep pressure gradient in the core beyond the pedestal top broadens eigenfunction profiles of unstable modes and possibly induces subsequent instabilities. In the subsequent instabilities, when a large energy is transported to the vicinity of the separatrix by the instabilities, a subsequent instability arises near the separatrix and makes an additional loss.

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Advanced tokamak research with integrated modeling in JT-60 Upgrade

Hayashi

Team²

2010

Physics of Plasmas

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Researches on advanced tokamak (AT) have progressed with integrated modeling in JT-60 Upgrade [N. Oyama et al., Nucl. Fusion 49, 104007 (2009)]. Based on JT-60U experimental analyses and first principle simulations, new models were developed and integrated into core, rotation, edge/pedestal, and scrape-off-layer (SOL)/divertor codes. The integrated models clarified complex and autonomous features in AT. An integrated core model was implemented to take account of an anomalous radial transport of alpha particles caused by Alfven eigenmodes. It showed the reduction in the fusion gain by the anomalous radial transport and further escape of alpha particles. Integrated rotation model showed mechanisms of rotation driven by the magnetic-field-ripple loss of fast ions and the charge separation due to fast-ion drift. An inward pinch model of high-Z impurity due to the atomic process was developed and indicated that the pinch velocity increases with the toroidal rotation. Integrated edge/pedestal model clarified causes of collisionality dependence of energy loss due to the edge localized mode and the enhancement of energy loss by steepening a core pressure gradient just inside the pedestal top. An ideal magnetohydrodynamics stability code was developed to take account of toroidal rotation and clarified a destabilizing effect of rotation on the pedestal. Integrated SOL/divertor model clarified a mechanism of X-point multifaceted asymmetric radiation from edge. A model of the SOL flow driven by core particle orbits which partially enter the SOL was developed by introducing the ion-orbit-induced flow to fluid equations.

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Pedestal Characteristics of H-Mode Plasmas in JT-60U and ASDEX Upgrade

Cited by 5 publications

References 29 publications

Integrated simulation of ELM triggered by a pellet through energy absorption and transport enhancement

Integrated simulation of ELM triggered by a pellet through energy absorption and transport enhancement

Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas

Advanced tokamak research with integrated modeling in JT-60 Upgrade

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