Search

JT-60SA tokamak is equipped with an ECRF system since the beginning of its operational phase. Starting from two gyrotrons units during the Integrated Commissioning, applicable for core heating, assisted breakdown and assisted Wall Conditioning, the system capabilities will be progressively extended from the Initial Research phase for wider applications. The development of the full current plasma H mode scenario 2 (inductive, type I ELM, Ip=5.5 MA, BT=2.25 T, q95=3) is among the first scientific objectives of the research program. In preparation of this, predictive modelling of the current ramp-up in scaled versions of scenario 2 is being done, based on parameters previously published. In this scenario the ECRF power is injected from an early phase of the discharge. Such modelling provides the kinetic profiles giving the opportunity to estimate the expected amount of EC stray radiation during the ramp-up phase when the EC power absorption might be less than 100% and consequently the potential risk of damage of the in-vessel components is higher.

For the first time, over five confinement times, the self-consistent flux driven time evolution of heat, momentum transport and particle fluxes of electrons and multiple ions including Tungsten (W) is modeled within the integrated modeling platform JETTO (Romanelli et al 2014 Plasma Fusion Res. 9 1–4), using first principle-based codes: namely, QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036) for turbulent transport and NEO (Belli and Candy 2008 Plasma Phys. Control. Fusion 50 95010) for neoclassical transport. For a JET-ILW pulse, the evolution of measured temperatures, rotation and density profiles are successfully predicted and the observed W central core accumulation is obtained. The poloidal asymmetries of the W density modifying its neoclassical and turbulent transport are accounted for. Actuators of the W core accumulation are studied: removing the central particle source annihilates the central W accumulation whereas the suppression of the torque reduces significantly the W central accumulation. Finally, the presence of W slightly reduces main ion heat turbulent transport through complex nonlinear interplays involving radiation, effective charge impact on ITG and collisionality. EURATOM 633053

We report on simulations aimed at optimizing external heating using neutral beam injection (NBI) and radiofrequency waves in the ion cyclotron range of frequencies (ICRF) for high fusion yield in the JET tokamak. In this paper, D and DT plasmas are analyzed taking into account the NBI+RF synergy focusing on two different minority ICRF schemes, He and H, respectively. Our results show that by increasing external heating power to the maximum power available, the fusion neutron rate can be enhanced in D plasma by a factor of 2-3 with respect to our reference record D discharge. Regarding the DT plasma we present the external heating performance under the variation of key plasma parameters. We also study the impact of the effects of ICRH to the fusion yield and show that the ICRH power results in an enhanced fusion yield in the whole parameter space studied. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Dani Gallart would like to express his gratitude to “La Caixa” for support of his PhD studies.

Control of instabilities such as ELMs and sawteeth is considered an important ingredient in the development of reactor-relevant scenarios. Various forms of ELM pacing have been tried in the past to influence their behavior using external perturbations. One of the main problems with these synchronization experiments resides in the fact that ELMs are periodic or quasi-periodic in nature. Therefore, after any pulsed perturbation, if one waits long enough, an ELM is always bound to occur. To evaluate the effectiveness of ELM pacing techniques, it is crucial to determine an appropriate interval over which they can have a real influence and an effective triggering capability. In this paper, three independent statistical methods are described to address this issue: Granger causality, transfer entropy and recurrence plots. The obtained results for JET with the ITER-like wall (ILW) indicate that the proposed techniques agree very well and provide much better estimates than the traditional heuristic criteria reported in the literature. Moreover, their combined use allows for the improvement of the time resolution of the assessment and determination of the efficiency of the pellet triggering in different phases of the same discharge. Therefore, the developed methods can be used to provide a quantitative and statistically robust estimate of the triggering efficiency of ELM pacing under realistic experimental conditions.

The compatibility of two operational constraints—operation above the L–H power threshold and at low power to divertor—is examined for ITER long pulse H-mode and hybrid scenarios in integrated core–scrape off layer (SOL)–divertor modelling including impurities (intrinsic Be, He, W and seeded Ne). The core thermal, particle and momentum transport is simulated with the GLF23 transport model tested in the self-consistent simulations of temperatures, density and toroidal rotation velocity in JET hybrid discharges and extrapolated to ITER. The beneficial effect of toroidal rotation velocity on fusion gain is shown. The sensitivity studies with respect to operational (separatrix and pedestal density, Ne gas puff) and unknown physics (W convective velocity and perpendicular diffusion in SOL as well as W prompt re-deposition) parameters are performed to determine their influence on the operational window and fusion gain.