The observation of small ELM post-cursor mode in EAST

A ‘post-cursor' quasi-coherent mode with frequency ～50 k Hz has been observed following the crash of small edge localized modes(ELMs) in the Experimental Advanced Superconducting Tokamak by using a reciprocating Langmuir probe system inserted at the outboard midplane.This mode with strong potential and magnetic perturbations propagates in the electrondiamagnetic drift direction in the laboratory frame.In addition,these quasi-coherent fluctuations appear to be modulated by a MHD mode with lower frequency(～5 k Hz).The bi-coherence analysis shows that the post-cursor mode and the MHD mode have nonlinear interaction through three-wave coupling.The understanding on post-cursor mode can enhance our knowledge of ELMs and pedestal physics,and give new insight into the ELM process itself.     

Design and platform testing of the compact torus central fueling device for the EAST tokamak

Compact torus(CT) injection is a highly promising technique for the central fueling of future reactor-grade fusion devices since it features extremely high injection velocity and relatively high plasma mass. Recently, a CT injector for the EAST tokamak, EAST-CTI, was developed and platform-tested. In the first round of experiments conducted with low parameter settings, the maximum velocity and mass of the CT plasma were 150 km·s^-1 and 90 μg, respectively.However, the parameters obtain...     

实战VQF

ＴｗｉｎＶＱ 即 ＶＱＦ是由 Ｎｉｐｐｏｎ Ｔｅｌｅ－ｇｒａｐｈ ａｎｄ Ｔｅｌｅｐｈｏｎｅ（ＮＴＴ）开发的一种音频压缩技术。经过权威评测,认为这是一种优于 ＭＰＥＧ ＬａｙｅｒⅢ（ＭＰ３）的技术。在音频压缩率和音质上,ＶＱＦ比起ＭＰ３有很大的优势。ＶＱＦ采用了与ＭＰ３截然不同的音频压缩技术,它的音频压缩率比ＩＳＯ标准的ＭＰＥＧ音频压缩率高出近一倍,可以达到１：１８至１：２０左右甚至更高。而ＭＰ３压缩率一般只有１：１２左右,可见ＶＱＦ在音频压缩比率上的优势已经明显超越了 ＭＰ３。当 ＶＱＦ以４４ＫｈＺ－８…     

Blob properties in I-mode and ELM-free H-mode compared to L-mode on EAST

The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak, including the blob detection rate N_b,size δ_b,lifetime τ_b and radial velocity v_r,b.The blob properties in L-mode and I-mode are similar, and those in ELM-free H-mode are different to them. The blob Nbis smaller while τbis larger in H-mode. The experimental blob sizeδband velocity scalings v_r,b-δ_b show a good agre...     

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

Lithium Beam Emission Spectroscopy systems in the outer midplane and divertor Langmuir probe arrays embedded in the divertor target plates, are utilized to investigate the scrape-off layer (SOL) blob transition and its relation with divertor detachment on EAST. The blob transition in the near SOL is observed during the density ramp-up phase. When the plasma density, normalized to the Greenwald density limit, exceeds a threshold of fGW ∼ 0.5, the blob size and lifetime increases by 2 – 3 times, while the blob detection rate decreases by about 2 times. In addition, a weak density shoulder is observed in the near SOL region at the same density threshold. Further analysis indicates that the divertor detachment is highly correlated with the blob transition, and the density threshold of blob transition is consistent with that of the access to the outer divertor detachment. The potential physical mechanisms are discussed. These results could be useful for the understanding of plasma-wall interaction issues in future devices that will operate under a detached divertor and high density conditions (over the blob transition threshold).     

Plasma edge density fluctuation measurements via lithium beam emission spectroscopy on EAST

Accurate and stable measurements of edge density fluctuation with high spatio-temporal resolution have been achieved by the lithium beam emission spectroscopy (Li-BES) diagnostic on experimental and advanced superconducting tokamak (EAST). The new narrower band interference filter exhibits good ability to suppress background emission signal even under strong lithium coating of the tokamak. The raw data measured by channels at different spatial locations in avalanche photo diode camera with high chopping frequency show good consistency. Based on the detected experimental data, detailed information of density profile and fluctuation structures is obtained. A clear edge coherent mode in the auto-power spectrum is observed in pedestal region, which is regarded as the dominant factor for the strong pedestal density fluctuation amplitude. The cross-power spectrum analysis further excludes the additional effects of common-mode noises and non-local perturbation, demonstrating that the detected fluctuation is only caused by local density fluctuation. The normalized radial and poloidal wave-number spectra can specify the quantitative changes of radial wavenumber (kr) and poloidal wavenumber (kθ) during the pedestal density fluctuation phase. This new Li-BES system, which can provide more accurate experimental data, allows further studies of edge density fluctuation and complex transport process on EAST.