Advances in the physics studies for the JT-60SA tokamak exploitation and research plan

JT-60SA, the largest tokamak that will operate before ITER, has been designed and built jointly by Japan and Europe, and is due to start operation in 2020. Its main missions are to support ITER exploitation and to contribute to the demonstration fusion reactor machine and scenario design. Peculiar properties of JT-60SA are its capability to produce long-pulse, high-β, and highly shaped plasmas. The preparation of the JT-60SA Research Plan, plasma scenarios, and exploitation are producing physics results that are not only relevant to future JT-60SA experiments, but often constitute original contributions to plasma physics and fusion research. Results of this kind are presented in this paper, in particular in the areas of fast ion physics, highbeta plasma properties and control, and non-linear edge localised mode stability studies.EURATOM 63305

Plasma diagnostics in TFTR using emission of cyclotron radiation at arbitrary frequencies

Emission of cyclotron radiation at arbitrary wave frequency for diagnostic purposes is discussed. It is shown that the radiation spectrum at arbitrary frequencies is more informative than the first few harmonics and it is suited for diagnosis of superthermal electrons without any {open_quotes}ad hoc{close_quotes} value of the wall reflection coefficient. Thermal radiation from TFTR is investigated and it is shown that the bulk and the tail of the electron momentum distribution during strong neutral beam injection is a Maxwellian with a single temperature in all ranges of electron energies

Experimental investigation of fast electron diffusion during ECRH

The spatial diffusion of fast electrons created by electron cyclotron resonant heating (ECRH) is examined using electron cyclotron emissions viewed along a nearly vertical chord in the TEXT-U tokamak. Enhanced emission at frequencies downshifted from the cold cyclotron frequency is attributed to non-thermal electrons. The emission spectra during ECRH are consistent with the presence of low density suprathermal electrons. Comparison of the spectra measured during ECRH with a bounce averaged Fokker-Planck code which incorporates the effects of magnetic and/or electrostatic turbulence on the distribution function, shows that the level of magnetic fluctuations in the center of TEXT-U is between 3 and 5 {times} 10{sup {minus}5}. This level of magnetic fluctuation is a factor of 2 to 5 too small to explain the transport of thermal electrons (E {approximately} 1 keV) in TEXT. Thus, magnetic fluctuations are an unlikely major cause of the transport of thermal electrons in TEXT

A control-oriented model of the current profile in Tokamak plasma

International audienceThis paper proposes a control-oriented approach to the tokamak plasma current profile dynamics. It is established based on a consistent set of simplified relationships, in particular for the microwave current drive sources, rather than exact physical modelling. Assuming that a proper model for advanced control schemes can be established using the socalled cylindrical approximation and neglecting the diamagnetic effects, we propose a model that focuses on the flux diffusion (from which the current profile is inferred). Its inputs are some real-time measurements available on modern tokamaks and the effects of some major actuators, such as the magnetic coils, Lower Hybrid (LHCD), Electron and Ion Cyclotron Frequency (ECCD and ICRH) systems, are particularly taken into account. More precisely, the non-inductive current profile sources are modelled as 3-parameters functions of the control inputs derived either from approximate theoretical formulae for the ECCD and bootstrap terms or from experimental scaling laws specifically developed from Hard X-ray Tore Supra data for the LHCD influence. The use of scaling laws in this model reflects the fact that the operation of future reactors will certainly depend upon a great number of scaling laws and specific engineering parameters. The discretisation issues are also specifically addressed, to ensure the robustness with respect to discretisation errors and the efficiency (in terms of computation time) of the associated algorithm. This model is compared with experimental results and the CRONOS solver for Tore Supra Tokamak

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

Lista completa de autores: Yoshida, M. ; Giruzzi, G.; Aiba, N.; Artaud, J. F.; Ayllon-Guerola, J.; Balbinot, L.; Beeke, O.; Belonohy, E.; Bettini, P.; Bin, W.; Bierwage, A.; Bolzonella, T.; Bonotto, M.; Boulbe, C.; Buermans, J.; Chernyshova, M.; Coda, S.; Coelho, R.; Davis, S.; Day, C.; De Tommasi, G.; Dibon, M.; Ejiri, A.; Falchetto, G.; Fassina, A.; Faugeras, B.; Figini, L.; Fukumoto, M.; Futatani, S.; Galazka, K.; García, J.; García-Muñoz, M.; Garzotti, L.; Giacomelli, L.; Giudicotti, L.; Hall, S.; Hayashi, N.; Hoa, C.; Honda, M.; Hoshino, K.; Iafrati, M.; Iantchenko, A.; Ide, S.; Iio, S.; Imazawa, R.; Inoue, S.; Isayama, A.; Joffrin, E.; Kamiya, K.; Ko, Y.; Kobayashi, M.; Kobayashi, T.; Kocsis, G.; Kovacsik, A.; Kurki-Suonio, T.; Lacroix, B.; Lang, P.; Lauber, P.; Louzguiti, A.; Luna, E. de la; Marchiori, G.; Mattei, M.; Matsuyama, A.; Mazzi, S.; Mele, A.; Michel, F.; Miyata, Y.; Morales, J.; Moreau, P.; Moro, A.; Nakano, T.; Nakata, M.; Narita, E.; Neu, R.; Nicollet, S.; Nocente, M.; Nowak, S.; Orsitto, F. P.; Ostuni, V.; Ohtani, Y.; Oyama, N.; Pasqualotto, R.; Pegourie, B.; Perelli, E.; Pigatto, L.; Piccinni, C.; Pironti, A.; Platania, P.; Ploeckl, B.; Ricci, D.; Roussel, P.; Rubino, G.; Sano, R.; Sarkimaki, K.; Shinohara, K.; Soare, S.; Sozzi, C.; Sumida, S.; Suzuki, T.; Suzuki, Y.; Szabolics, T.; Szepesi, T.; Takase, Y.; Takech, M.; Tamura, N.; Tanaka, K.; Tanaka, H.; Tardocchi, M.; Terakado, A.; Tojo, H.; Tokuzawa, T.; Torre, A.; Tsujii, N.; Tsutsui, H.; Ueda, Y.; Urano, H.; Valisa, M.; Vallar, M.; Vega, J.; Villone, F.; Wakatsuki, T.; Wauters, T.; Wischmeier, M.; Yamoto, S.; Zani, L.A large 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 DEMO have been clarified through those studies.Comisión Europea - EURATOM 63305

Measurement of the hot electrical conductivity in the PBX-M tokamak

A new method for the analysis of tokamak discharges in which the plasma current is driven by the combination of high-power rf waves and a dc electric field is presented. In such regimes, which are the most usual in rf current drive experiments, it is generally difficult to separate the different components of the plasma current, i.e., purely Ohmic, purely noninductive and cross terms. If the bilinear (in wave power and electric field) cross term is the dominant one, an explicit relation between the loop voltage drop and the injected power can be found. This relation involves two parameters, the purely rf current drive efficiency and the hot (power dependent) electrical conductivity. These can be simultaneously determined from a simple two-parameter fit, if the loop voltage drop is measured at several rf power levels. An application to lower hybrid current drive experiments in the PBX-M tokamak is presented. It is shown that the method also allows the independent evaluation of the average power absorption fraction and n{sup {parallel}} upshift

A study of MHD feedback stabilization in tokamaks with lower hybrid waves

Lower Hybrid Current Drive (LHCD) has been successfully employed in current profile control experiments and can be utilized to prevent MHD instabilities by tailoring the profile. Similarly, theory has shown that LHCD can be very effective in stabilizing MHD instabilities by feedback techniques: this experiment has not been tried yet. This paper addresses some of the practical aspects of such an experiment