[en] Full text: Turbulent transport and flow dynamics in Ohmic FT-2 tokamak plasmas are investigated. Measurements utilize highly localized state-of-the art backscattering while the turbulence simulations are performed with the global full-f nonlinear code ELMFIRE. The role of the geodesic acoustic mode in regulating turbulent transport is studied. Special emphasis is given to the isotope effect observed in tokamak anomalous transport scaling. (author)

[en] Full text: The hydrogen campaign completed at JET in 2016 has demonstrated isotope ratio control in JET-ILW using gas puffing and pellets for fuelling, neutral beam injection alone or in combination, with D_α/H_α spectroscopy as a diagnostic. The plasma properties such as confinement, L-H threshold, density limit depend on the isotope composition. The L-H transition power increases with the hydrogen concentration with a wide plateau in the range 0.2. (author)

[en] Full text: Toroidal Alfven eigenmodes (TAEs) during minor disruptions have been identified in the ohmic plasmas of the SUNIST spherical tokamak. The TAE modes are observed in the frequency range of 150-400 kHz. The mode structure analysis indicates the existence of both m/n = -3/-1 and -4/-1 harmonics, propagating in the electron diamagnetic direction in the laboratory frame of reference. These TAEs appear simultaneously with the generation of REs in the current quench phase, followed by a RE current plateau. (author)

[en] Full text: The suppression and mitigation of runaway electron (RE) is an urgent issue of large scale tokamak operation. The contribution of hot-tail effect, which arises from the fast thermal quench, is studied using Fokker-Planck simulation. It is found that if the thermal quench is fast enough to invoke the hot-tail effect, it may produce seed REs and enhance total RE current even in a high electron density plasma. (author)

[en] Full text: The SST-1 start-up studies and development of appropriate model has been initiated using electromagnetic field computation for active current carrying conductor and SST-1 vacuum vessel eddy characteristics. This electromagnetic model has been employed to predict individual electromagnetic field for active electromagnet such as vertical field coil (VF), poloidal field coil (PF), radial control coil (RCC), central solenoid (CS) and other active current carrying coil. This model can be also useful to determine the some other break-down parameter such as connection length, ionization length and electric field etc. (author)

[en] Full text: This paper presents the recent progress of a conceptual DEMO design in Japan. First, the divertor concept is built under feasible engineering technology. Second, the circulating power in DEMO is precisely investigated as for the cooling power and the water detritiation system to ensure substantial net electric power. Then, 3D eddy current analysis shows the prospect for plasma elongation ∼1.7 and increase the electric power output. Finally, safety analysis on an ex-vessel LOCA is carried out, and it is found that a vault of the tokamak cooling water system (TCWS) with a pressure suppression system (PSS) can mitigate it. (author)

[en] Full text: We investigate the effect of resistivity, mainly on pitch resonant responses induced by plasma rotation. As a confirmation of the newly developed code, we report that the detailed physics may not be important since the pitch resonant response is relatively weak at high resistivity and the penetration is strongly dependent on plasma rotation at low resistivity. At low resistivity, ion collisionality can affect the penetration of RMPs through poloidal flow. The preliminary quasilinear results with n = 0 parallel flow and radial electric field show that the torque induced by RMP may modify parallel flow significantly t > 10⁴t_A∼1 ms after RMP application. The detailed quasilinear responses will be presented with the possible implication on ELM suppression. (author)

[en] Full text: Since the first commissioning in February 2006, EAST cryogenic system has been in operation for eleven plasma experiment campaigns with high reliability. However, ten years have passed from the beginning of system operations. With requirements of EAST physical experiment, new users of cryogenic system have been added such as cryopump, pellet inject and NBI. Some upgrades have been implemented to improve the reliability and availability of cryogenic system. New warm compressors, turbines and cryogenic distribution system haven been constructed. EAST cryogenic control system has been upgraded in 2015 and put into operation the 11th campaign. This paper presents the upgrade solutions of cryogenic system in detail. At same time, the operational performance has been analyzed with further purpose to improve the cryogenic system reliability so as to guarantee the success of high performance plasma experiments in future. (author)

[en] Full text: The recent key physics of the laser fusion is how to make hot sparks for the alpha burning in the dense core. The fast ignition is expected to form a hot spark even with a nonuniform illumination configuration, such as with a counter-illumination one. By using both a high-repetition rate 10 J laser and a single-shot kJ laser, we have proposed and demonstrated a new concept for the fast-ignition scheme fusion, where main beams implode a shell target with counterbeam configuration and ultraintense lasers with the same configuration drive either hot electrons or ions or both, which has directly heated the core. Shock waves driven by ultraintense lasers are also powerful candidates for the core heating and are investigated. Combining these three fast-ignition schemes, we are demonstrating both the implosion and ignition to work well with counterbeam configuration. (author)

[en] Full text: Neoclassical accumulation of impurities in the core of hot stellarator plasmas is a known problem. The complexity of neoclassical transport in stellarators means that few analytic studies are available to support numerical modelling efforts, and a robust understanding of the parameter dependence of the impurity flux is still lacking. Therefore we present an extension of the existing analytic treatment for highly collisional plasmas, into the experimentally relevant mixed collisionality regime—where a dominant heavy, collisional, impurity is present in a collisionless bulk plasma, taken here to be in the 1/v regime. We find that temperature screening of the impurity flux by the bulk ion temperature gradient will arise. We also determine the bulk ion flow in the flux surface, and thus the effect of the impurity on the bulk ion contribution to the bootstrap current. (author)