Modelling of the JET current ramp-up experiments and projection to ITER

Voitsekhovitch, I.; Sips, A. C. C.; Alper, B.; Beurskens, M.; Coffey, I.; Conboy, J. E.; Gerbaud, T.; Giroud, C.; Johnson, T.; Köchl, F.; Luna, E. de la; McDonald, D. C.; Pavlenko, I. V.; Pereverzev, G.; Popovichev, S.; Saveliev, A. N.; Sergienko, G.; Sharapov, S. E.; Stamp, M.; Contributors, Jet‐Efda

doi:10.1088/0741-3335/52/10/105011

Cited by 19 publications

(27 citation statements)

References 28 publications

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“…Also in AUG the neoclassical calculation yielded a too fast current penetration during the ohmic ramp-up phase [5]. On the other hand, the calculated current diffusion in the later part of the ramp-up in JET can be matched with the observations, by adjusting the profiles of Z eff and T e within the experimental uncertainties [6]. Moreover, the observed relaxation of the q profile after the L-H transition in JET is reported to be in agreement with neoclassical calculations [7].…”

Section: Introductionmentioning

confidence: 73%

“…Validation on the ramp-up phase of JET, AUG and Tore Supra [6,8,9] has shown that both empirical scaling based models and the semi-empirical Bohm/gyro-Bohm model (L-mode version, ITB shear function off, [10]) yield a good reproduction of this phase for considered discharges, in terms of T e profile and l i . Therefore these two models have been used in the reported work.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore these two models have been used in the reported work. The Coppi-Tang model [11] did a good job in reproducing the current ramp-up phase in DIII-D [12], but strongly underestimated thermal transport in JET [6]; hence this model will not be used in this work.…”

Section: Introductionmentioning

confidence: 99%

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Optimizing the current ramp-up phase for the hybrid ITER scenario

Hogeweij¹,

Artaud²,

Casper³

et al. 2012

Nucl. Fusion

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The current ramp-up phase for the ITER hybrid scenario is analyzed with the CRONOS integrated modelling suite. The simulations presented in this paper show that the heating systems available at ITER allow, within the operational limits, the attainment of a hybrid q profile at the end of the current ramp-up. A reference ramp-up scenario is reached by a combination of NBI, ECCD (UPL) and LHCD. A heating scheme with only NBI and ECCD can also reach the target q profile; however, LHCD can play a crucial role in reducing the flux consumption during the ramp-up phase. The optimum heating scheme depends on the chosen transport model, and on assumptions on parameters like n e peaking, edge T e,i and Z eff. The sensitivity of the current diffusion on parameters that are not easily controlled, shows that development of real time control is important to reach the target q profile. A first step in that direction has been indicated in this paper. Minimizing resistive flux consumption and optimizing the q profile turn out to be conflicting requirements. A trade-off between these two requirements has to be made. In this paper it is shown that fast current ramp with L-mode current overshoot is at the one extreme, i.e. optimum q profile at the cost of increased resistive flux consumption, whereas early H-mode transition is at the other extreme.

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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

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Optimizing the current ramp-up phase for the hybrid ITER scenario

Hogeweij¹,

Artaud²,

Casper³

et al. 2012

Nucl. Fusion

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show abstract

“…It has recently become clear that stringent constraints are put on the operational scenario of the ITER current rampup (CRU) and current ramp-down (CRD) phases, for several reasons discussed in the literature ( [1] and references therein). In this respect, most of the focus now in the ITER modelling activity, see for example [2][3][4][5][6][7][8][9], is on predicting how the relevant plasma parameters will evolve during the current ramp-up and ramp-down phases, allowing optimization studies before the machine is built and operated.…”

Section: Introductionmentioning

confidence: 99%

Confinement and transport properties during current ramps in the ASDEX Upgrade tokamak

et al. 2011

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A detailed analysis of experimental data from the ASDEX Upgrade tokamak is carried out to shed light on the properties of confinement and transport in the current ramp-up and ramp-down phases of the plasma discharge. The experimental database is used to identify the relevant ranges of parameters explored during the ramp-up and the ramp-down. The energy confinement time observed in the two ramps displays interesting evolution, in many cases attaining different values at the same current level between ramp-up and ramp-down. The possible reasons for this behaviour are investigated. Interpretative transport simulations are used as a tool to clarify the interplay between different parameters, which are coupled in a non-linear way. In addition, a theory-based transport model is used to understand the behaviour of confinement as observed in the experiment, evidencing the role of both turbulent and neoclassical transport. Linear gyrokinetic calculations are performed to identify the relevant turbulence regime, showing that a broad range of frequencies, in the trapped electron modes (TEMs) and in the ion temperature gradient modes (ITGs) regimes, is explored during both the ramp-up and ramp-down. In the same framework, a quasi-linear model is applied to calculate the value of the local logarithmic density gradient and compare it with the experimental value. Finally, first non-linear simulations of heat transport during the current ramps are presented.

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“…These parameters exhibit strong nonlinear dependencies. Recent experiments on DIII-D [2,3] and other tokamaks [4,5] have sought to simulate an ITER-like ramp-up in order to test these models, as well as to optimize the ramp-up scenario [6].…”

Section: Introductionmentioning

confidence: 99%

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

McKee¹,

Austin²,

Boedo³

et al. 2017

Nucl. Fusion

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Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75 < ρ < 0.9 are transiently reduced to exceptionally low levels during early times and from 0.8 < ρ < 0.9 at late times in the ramp-up in a manner that is different from behavior observed during steady-state plasma conditions with similar values of q 95 . Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don't exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. This indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.

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Modelling of the JET current ramp-up experiments and projection to ITER

Cited by 19 publications

References 28 publications

Optimizing the current ramp-up phase for the hybrid ITER scenario

Optimizing the current ramp-up phase for the hybrid ITER scenario

Confinement and transport properties during current ramps in the ASDEX Upgrade tokamak

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

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