Construction And Experiments Of High Field Side Probe On EAST

Process of particle and energy transport in scrape-off layer (SOL) in tokamak hugely affects the practicability of fusion devices. The heat flux scaling on ITER divertor shows that additional method must be adopt to handle the peak of the high heat load in regimes it planned to operated on to extend the life-span of its divertor. The particles, including impurities, transport process and energy transport process, the plasma-wall interaction and the atomic molecular process in the edge of main plasma of tokamak all coupled together, which is to exert influence on the development of future devices of fusion.High field side (HFS) above inner plate of divertor is in upstream of the flow act on. The measurement made in this region together with the parameters given by divertor probe array on the plate will give a complete picture of transport in HFS. And together with the low field side (LFS) probe measurements, whole field of poloidal sector of the tokamak parameters is provided. But most of the fusion experimental devices are lacking of techniques in measuring this region.Parallel flow dominates the transport process in SOL region. Because the flow is strongly connected the rotation in plasma core, turbulent transport, flow shear etc, the observation and analysis of the flow is of great importance. Mach probe array can facilitate the measurement of the parallel flow and a large fraction of local sound speed of SOL parallel flow is already observed on lots of tokamaks. The drift induced transport process depict by electric field drift induced flow and the magnetic gradient and magnetic curvature induced non-divergence-free part of the flow in the pressure gradient in SOL region has long been verified and described by neo-classical theory of transport. But the TF coil magnetic field reversal experiments implies that a transport driven follow component which is originated from low field side is the main reason of flow formation in SOL far from outer poloidal position. The drift perpendicular to local field line, which should not be neglected, can be roughly given by measurement of Langmuir-probe too as it is constituted by E cross B perpendicular drift and pressure gradient cross B perpendicular drift.HFS probe on EAST have been mounted on and experiments conducted in 2014 campaign and the data on EAST HFS SOL obtained. Addressed by analysis, there is the existence of 0.7 of the sonic parallel flow in near SOL primarily driven by outer mid-plane enhanced radial directed transport induced by pressure asymmetry in poloidal direction. Turbulence in HFS appears to be Gaussian which is a sign of non-existence of turbulent structure here in quiescent state. Type-Ⅰ ELM signal caught by HFS probe and the analysis of data shows that the structure is formed in LFS and periodically transmitted to HFS. Energetic electron caught in HFS SOL and it is transmitted from LFS too, which can be drawn from ELM onset ion saturation signal caught by HFS-probe.Since EAST is a super conducting tokamak which its design is for long pulse operation with a low level of recycling, the expedition for long pulse high quality plasma operation will be used as a reference for future fusion devices as ITER. In support of this, the HFS probe, which is adapted to the characteristic of EAST and the EAST parameter, will provide data on its daily operation.