Optimizing the Current Ramp-Up Phase for Hybrid ITER Scenario

Hogeweij, D.; Artaud, Jean-François; Casper, T.; Citrin, J.; Imbeaux, F.; Köchl, F.; Litaudon, X.; Voitsekhovitch, I.

doi:10.1585/pfr.7.2403063

Cited by 3 publications

(5 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Starting with the current ramp-up phase an impact of external heating and current drive waveforms, timing of the L-H transition and plasma current waveform on the target q-profile and resistive flux consumption at the end of the current ramp-up have been investigated [43,44]. It has been shown that the q-profile with q 0 > 1 can be reached at the end of the current ramp-up phase with the heating systems available at ITER.…”

Section: Discussionmentioning

confidence: 99%

“…Access condition to the class of hybrid-like q-profiles (i.e. flat in the core and slightly above unity with a high magnetic shear in the gradient zone) during the prelude phase of the scenario is investigated with particular attention in this section [42][43][44]. The plasma current ramp-up phase is a critical phase of the scenario preparation where the optimized q-profile should be reached while deleterious MHD instabilities for confinement and stability have to be avoided, flux consumption has to be minimized, and this has to be achieved within ITER operational constrain.…”

Section: Current Profile Optimization During Current Ramp-up Phasementioning

confidence: 99%

See 1 more Smart Citation

Modelling of hybrid scenario: from present-day experiments towards ITER

et al. 2013

View full text Add to dashboard Cite

The ‘hybrid’ scenario is an attractive operating scenario for ITER since it combines long plasma duration with the reliability of the reference H-mode regime. We review the recent European modelling effort carried out within the Integrated Scenario Modelling group which aims at (i) understanding the underlying physics of the hybrid regime in ASDEX-Upgrade and JET and (ii) extrapolating them towards ITER. JET and ASDEX-Upgrade hybrid scenarios performed under different experimental conditions have been simulated in an interpretative and predictive way in order to address the current profile dynamics and its link with core confinement, the relative importance of magnetic shear, s, and E × B flow shear on the core turbulence, pedestal stability and H–L transition. The correlation of the improved confinement with an increased s/q at outer radii observed in JET and ASDEX-Upgrade discharges is consistent with the predictions based on the GLF23 model applied in the simulations of the ion and electron kinetic profiles. Projections to ITER hybrid scenarios have been carried out focusing on optimization of the heating/current drive schemes to reach and ultimately control the desired plasma equilibrium using ITER actuators. Firstly, access condition to the hybrid-like q-profiles during the current ramp–up phase has been investigated. Secondly, from the interpreted role of the s/q ratio, ITER hybrid scenario flat-top performance has been optimized through tailoring the q-profile shape and pedestal conditions. EPED predictions of pedestal pressure and width have been used as constraints in the interpretative modelling while the core heat transport is predicted by GLF23. Finally, model-based approach for real-time control of advanced tokamak scenarios has been applied to ITER hybrid regime for simultaneous magnetic and kinetic profile control.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Current Profile Optimization During Current Ramp-up Phasementioning

confidence: 99%

Modelling of hybrid scenario: from present-day experiments towards ITER

et al. 2013

View full text Add to dashboard Cite

show abstract

“…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, internal transport barrier (ITB) shear function off, [10]) yield a good reproduction of this phase for considered discharges, in terms of the T e profile and l i . Therefore these two models have been used in the reported work.…”

Section: Introductionmentioning

confidence: 99%

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

Hogeweij¹,

Artaud²,

Casper³

et al. 2012

Nucl. Fusion

View full text Add to dashboard Cite

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.

show abstract

“…The current ramp-up phase in tokamaks has recently attracted the attention of experimentalists [1][2][3] and modellers [1,[4][5][6] in connection with future experiments on ITER. The important objectives of the current ramp-up phase on ITER are maintenance of a current density profile compatible with vertical stability of the plasma column [7] and the formation of the target q-profile favourable for subsequent burn phase (with q 0 above one for an extended sawtoothfree H-mode and hybrid scenario or reversed q-profile for the advanced operation with an internal transport barrier (ITB)) [8].…”

Section: Introductionmentioning

confidence: 99%

“…Later on the validation of the Bohm-gyroBohm model [10] has been performed also for OH and LHCD assisted current ramp-up phase of the H-mode discharges of JET [6]. Finally, the empirical formula for the thermal electron diffusivity which has a parabolic profile multiplied by a free coefficient adjusted at each time step to provide a prescribed H 98y factor has been validated against the OH current ramp-up discharges of JET, performed at two different current ramp rates, and applied to the modelling of the ITER ramp-up phase [5].…”

Section: Introductionmentioning

confidence: 99%

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

Voitsekhovitch¹,

Sips²,

Alper³

et al. 2010

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

The current ramp up phase of ITER demonstration discharges, performed at JET, is analysed and the capability of the empirical L-mode Bohm-gyroBohm and CoppiTang transport models as well as the theory-based GLF23 model to predict the temperature evolution in these discharges is examined. The analysed database includes ohmic (OH) plasmas with various current ramp rates and plasma densities and the L-mode plasmas with the ion cyclotron radio frequency (ICRF) and neutral beam injection (NBI) heating performed at various ICRF resonance positions and NBI heating powers. The emphasis of this analysis is a data consistency test, which is particularly important here because some parameters, useful for the transport model validation, are not measured in OH and ICRF heated plasmas (e.g. ion temperature, effective charge). The sensitivity of the predictive accuracy of the transport models to the unmeasured data is estimated. It is found that the Bohm-gyroBohm model satisfactorily predicts the temperature evolution in discharges with central heating (the rms deviation between the simulated and measured temperature is within 15%), but underestimates the thermal electron transport in the OH and off-axis ICRF heated discharges. The Coppi-Tang model strongly underestimates the thermal transport in all discharges considered. A re-normalisation of these empirical models for improving their predictive capability is proposed. The GLF23 model, strongly dependent on the ion temperature gradient and tested only for NBI heated discharges with measured ion temperatures, predicts accurately the temperature in the low power NBI heated discharge (rms < 10%) while the discrepancy with the data increases at high power.Based on the analysis of the JET discharges, the modelling of the current ramp up phase for the H-mode ITER scenario is performed with particular emphasis on the 3 sensitivity of the duration of the sawtooth-free current ramp up phase to transport model. 4

show abstract

Optimizing the Current Ramp-Up Phase for Hybrid ITER Scenario

Abstract: This paper reports on a systematic effort to optimize the current ramp-up phase for the ITER hybrid scenario, and to assess the sensitivity of the results to the assumptions made.

Cited by 3 publications

References 9 publications

Modelling of hybrid scenario: from present-day experiments towards ITER

Modelling of hybrid scenario: from present-day experiments towards ITER

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

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

Contact Info

Product

Resources

About