Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation

Alarge superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMOhave been clarified through those studies.Peer ReviewedArticle escrit per 127 autors/autores: M Yoshida, G Giruzzi, N Aiba, J F Artaud, J Ayllon-Guerola, L Balbinot, OBeeke, E Belonohy, P Bettini, W Bin, A Bierwage, T Bolzonella, M Bonotto, CBoulbe, J Buermans, M Chernyshova, S Coda, R Coelho, S Davis, C Day, GDeTommasi, M Dibon, A Ejiri, G Falchetto, A Fassina, B Faugeras, L Figini, M Fukumoto, S Futatani, K Galazka, J Garcia, M Garcia-Muñoz, L Garzotti, L Giacomelli, L Giudicotti, S Hall, N Hayashi, C Hoa, M Honda, K Hoshino, M Iafrati, A Iantchenko, S Ide, S Iio, R Imazawa, S Inoue, A Isayama, E Joffrin, K Kamiya, Y Ko, M Kobayashi, T Kobayashi, G Kocsis, A Kovacsik, T Kurki-Suonio, B Lacroix, P Lang, Ph Lauber, A Louzguiti, E de la Luna, G Marchiori, M Mattei, A Matsuyama, S Mazzi, A Mele, F Michel, Y Miyata, J Morales, P Moreau, A Moro, T Nakano, M Nakata, E Narita, R Neu, S Nicollet, M Nocente, S Nowak, F P Orsitto, V Ostuni, Y Ohtani, N Oyama, R Pasqualotto, B Pégourié, E Perelli, L Pigatto, C Piccinni, A Pironti, P Platania, B Ploeckl, D Ricci, P Roussel, G Rubino, R Sano, K Särkimäki, K Shinohara, S Soare, C Sozzi, S Sumida, T Suzuki, Y Suzuki, T Szabolics, T Szepesi, Y Takase, M Takech, N Tamura, K Tanaka, H Tanaka, M Tardocchi, A Terakado, H Tojo, T Tokuzawa, A Torre, N Tsujii, H Tsutsui, Y Ueda, H Urano, M Valisa, M Vallar, J Vega, F Villone, T Wakatsuki, T Wauters, M Wischmeier, S Yamoto, L ZaniPostprint (published version

Simulations of combined ICRF and NBI heating for high fusion performance in JET

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.Postprint (author's final draft

Sviluppo di un sistema di iniezione di proiettili di idrogeno solido per il controllo della densita' di plasma nell'esperimento RFX

Dottorato di ricerca in energetica. 8. ciclo. A.a. 1994-95Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

On the Use of Transfer Entropy to Investigate the Time Horizon of Causal Influences between Signals

Understanding the details of the correlation between time series is an essential step on the route to assessing the causal relation between systems. Traditional statistical indicators, such as the Pearson correlation coefficient and the mutual information, have some significant limitations. More recently, transfer entropy has been proposed as a powerful tool to understand the flow of information between signals. In this paper, the comparative advantages of transfer entropy, for determining the time horizon of causal influence, are illustrated with the help of synthetic data. The technique has been specifically revised for the analysis of synchronization experiments. The investigation of experimental data from thermonuclear plasma diagnostics proves the potential and limitations of the developed approach

ECRF stray radiation studies in preparation of the operations of JT-60SA

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

Characterisation of the L-mode scrape off layer in MAST: decay lengths

This work presents a detailed characterisation of the MAST Scrape Off Layer in L-mode. Scans in line averaged density, plasma current and toroidal magnetic field were performed. A comprehensive and integrated study of the SOL was allowed by the use of a wide range of diagnostics. In agreement with previous results, an increase of the line averaged density induced a broadening of the midplane density profile. This increase was not correlated with divertor detachment, as confirmed by the systematic increase of the target ion flux and decrease of the ${{D}_{\gamma}}/{{D}_{\alpha}}$ emission. Also, no clear correlation is found with the density of the neutral particles at the wall. At comparable density levels, discharges with higher current did not show broadening. Outer target ion saturation current and heat flux decay lengths were measured and compared with midplane data. For the saturation current, the upstream projections of the target values, based on diffusive models, did not match the midplane measurements, neither in amplitude nor in trend, while agreement was found for the heat fluxes, suggesting a different perpendicular transport mechanism for the two channels. Furthermore, the value of the target heat flux decay length was quite insensitive to changes in the thermodynamic conditions, in agreement with recent scaling laws. In all the cases studied, sawtooth oscillations were present but they simply rescaled self-similarly the target profiles. The separatrix conditions changed significantly during a sawtooth cycle, but the target heat flux decay length and divertor spreading factor remained nearly constant, indicating that these quantities are rather insensitive to the upstream thermodynamic state of the SOL

Gyrokinetic simulations of particle transport in pellet fuelled JET discharges

Pellet injection is a likely fuelling method of reactor grade plasmas. When the pellet ablates, it will transiently perturb the density and temperature profiles of the plasma. This will in turn change dimensionless parameters such as a/Ln,a/LT and plasma β. The microstability properties of the plasma then changes which influences the transport of heat and particles. In this paper, gyrokinetic simulations of a JET L-mode pellet fuelled discharge are performed. The ion temperature gradient/trapped electron mode turbulence is compared at the time point when the effect from the pellet is the most pronounced with a hollow density profile and when the profiles have relaxed again. Linear and nonlinear simulations are performed using the gyrokinetic code GENE including electromagnetic effects and collisions in a realistic geometry in local mode. Furthermore, global nonlinear simulations are performed in order to assess any nonlocal effects. It is found that the positive density gradient has a stabilizing effect that is partly counteracted by the increased temperature gradient in the this region. The effective diffusion coefficients are reduced in the positive density region region compared to the intra pellet time point. No major effect on the turbulent transport due to nonlocal effects are observed

An analysis of the physics requirements for scenario control for the ECRF system of JT-60SA

那珂核融合研究所では現在、2020年からの実験開始に向けて、超伝導トカマクJT-60SAが建設中である。JT-60SAでは、電子サイクロトロン周波数帯(ECRF)の加熱/電流駆動装置が装備される予定であり、Initial Research Phaseには3MW、Integrated Research Phaseには7MWのミリ波がプラズマに入射される。ミリ波の周波数は110GHzまたは138GHzとすることが可能であり、ミリ波の入射時間は100秒間である。那珂核融合研究所では、JT-60SA用のジャイロトロン、伝送路、ランチャーなどのECRF装置が現在開発中である。本発表では、ECRFランチャーの最新の設計データを光学コードGRASPや光線追跡コードGRAYに適用してJT-60SAの加熱/電流駆動特性を評価した結果を報告する。解析対象としたプラズマはJT-60SAリサーチプランで典型シナリオとして掲げられているシナリオ2（プラズマ電流5.5MA、トロイダル磁場強度2.25Tのシナリオ）、シナリオ4（2.25TのITER形状プラズマ）、シナリオ5（定常運転）である。138GHzのミリ波により、2.25Tにおいても規格化小半径で0.2から0.8の範囲で加熱/電流駆動が可能であり、電流駆動密度は自発電流密度の半分〜同程度となる。1.7Tのシナリオ5においては、110GHzのミリ波を用いることにより、完全非誘導電流駆動において重要となる領域(規格化小半径で0.4〜0.7)において電流駆動が可能である