No abstract available

[en] To achieve better plasma density control, experimental advanced superconducting tokamak (EAST) has already equipped with gas puffing (GP), supersonic molecular beam injection (SMBI) and pellet injection (PI). During the past few years, lots of experiments and ameliorations have been done. The performance of the SMBI and gas puffing (GP) feedback systems were used and compared. And the preliminary result of pellet injection was also presented here. The results shows the PI and SMBI were more compatible to the long pulse high density discharge on EAST. (author)

[en] The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactions at EAST and some preliminary results for the optimizing RF performance will be presented. (author)

[en] Heat and particle loads on the plasma-facing components are among the most challenging points to be solved for ITER and a reactor design. Alternative magnetic configuration, such as the X-divertor, Super X-divertor and Snowflake divertor may enable tokamak operation at lower peak heat load than a standard Single Null divertor. This paper reports on the modelling of the variations of the second null point present in the advanced magnetic divertor, here so-called quasi-Snowflake configuration, and first experiments performed on the EAST tokamak in 2014. (author)

[en] In this paper a stochastic approach to solve the probability of backward runaway. A stochastic differential equation for electrons in fully ionized plasma is derived using Cadjan-lvanov method. An energy-preserving algorithm is presented. Using this method, the backward runaway probability is calculated statically. (author)

[en] Zonal flows, initially driven by ion-temperature-gradient turbulence, may evolve due to the neoclassic polarization in a collisionless tokamak plasma. In this presentation, the form of the residual zonal flow is presented for tokamak plasmas rotating toroidally at arbitrary velocity. The gyro-kinetic equation is analytically solved to give the expression of residual zonal flows with arbitrary rotating velocity. The zonal flow level decreases as the rotating velocity increases. The numerical evaluation is in good agreement with the previous simulation result for high aspect ratio tokamaks. (author)

[en] The secular dynamics of runaway electrons in Tokamak electromagnetic field is studied. The radiation effect is added into a relativistic volume-preserving algorithm to gain long-term stability of calculation. The results shows that the method we used is able to reveal the behavior of a runaway electron in configuration space. (author)

[en] The optimum scheme for geometric phase measurement in plasma is proposed. The theoretical values of geometric phase for the probe beams of EAST Polarimeter/Interferometer (POINT) system are calculated by path integration in parameter space and the influences of some controllable parameters on geometric phase are evaluated. The feasibility and problems of distinguishing geometric effect in the POINT signal are assessed. (author)

[en] The large helical device (LHD) Thomson scattering system measures electron temperature and density profiles of LHD plasmas along the LHD major radius. In the original design, an oblique backward scattering configuration with a typical scattering angle of 167-degree was adopted, and the laser pulses are simply absorbed by a beam dump after traveling through LHD plasma. Recently we removed the beam dump and installed a beam-returning mirror, a relay lens and an optical delay path of 30 m to observe forward Thomson scatting signals. In the forward scattering configuration, typical scattering angle is 13-degree. By combining the backward and forward scattering measurements, some applications will be possible. In this paper, extension of measurable temperature range and search of temperature anisotropy are discussed. (J.P.N.)

[en] The ion orbit loss and the formation of radial electric field Er in tokamak edge region are calculated. The ion orbit loss generates a negative Er, which in turn affects the ion loss. As a result, Er can saturates at either a low or a high value, depending on the plasma parameters. When the ion temperature in the plasma edge is higher than a threshold a self-sustaining growth in both the ion loss and Er is found, leading to a high saturation value of Er in the milliseconds time. This mechanism provides a possible explanation for the formation of the edge radial electric field during the L to H-mode transition observed in tokamak experiments. (author)