| Fusion energy is an ultimate solution to the energy crisis of human,which is safe,clean and can provide nearly unlimited energy.To utilize the controlled fusion energy,tokamak is a promising way.In past several decades,people have achieved many important results on Tokamak.However.there are still many problems for tokamak development,like heat load on plasma-facing components,plasma instabilities,plasma confinement performance and so on.Heat load on plasma-facing components is closely related with blobs in edge-SOL plasma as blobs play a significant role in plasma edge convective transport.On the other side,instabilities and plasma confinement performance have strong dependences on plasma scenario.Good scenario can improve plasma performance and bad scenario can even lead to terrible plasma disruption.This thesis can be divided into two parts.The first part is an investigation of blob behaviors on EAST and the second part is the research work about the advanced scenario for future reactorsWe spend three years to establish Lithium Beam Emission Spectroscopy system(Li-BES)on EAST and utlize many measures to improve the signal quality.The Li-BES system can provide high spatio-temporal electron density profiles and fluctuations of edge-SOL plasma,which is an artifact in researching edge plasma physicsWe investigate the blob behaviors on EAST by utilizing Li-BES system.The most stable theory blob size matches well with experiment measurements.Blob self-correlation time is positively correlated with blob size and anti-correlated with blob frequency.We also investigate the high density transition phenomenon.The density threshold is 0.5 times the Greenwald density.During line averaged plasma density ramping up phase.The blob size increase.Γblob significant increase and divertor detachment yield SOL density profiles flattening and λn dramatic increase.All these changes lead to the formation of SOL density shoulder.Furthermore,with the application of lower hybrid waves,it is discovered for the first time that blob fluctuation amplitude and associated blob radial transport flux are profoundly suppressed and high frequency turbulences are enhanced.The reductions of blob amplitude and transport flux are concomitant with the increase of SOL Er × B flow shear.Meanwhile,the blob eddy is strongly tilted and radial correlation length is reduced.All the measurements point towards an important influence of LHW induced Er× B flow shear on the suppression of blobsOn the other side,we also do a lot work on advanced scenarios.On EAST we investigate the relations between internal inductance li and LHW power proportion,plasma density,main plasma configuration parameters,like upper triangularity,lower triangularity,elongation,separatrix distance dRsep.It is found that li and dRsep are closely and inversely related through the LCFS.Two possible mechanisms are carried out.The first is that li and dRsep are closely connected via LCFS The second is that dRsep can influence the distribution of the LHW-induced fast electrons shifts towards the plasma edge.The results should be helpful to optimization of li in the future experiments on long-pulse operation of EAST.The EAST/DIII-D joint experiment is carried out to explore advanced scenarios for future reactors.In the joint experiment,based on the results of high βρ scenarios(achieving high q95.high qmin and hish βN simultaneously)in the previous experiment,we lower q95 and use high non-inductive current scenario with qmin>2 and reduced torque.Very high confinement.normalized fusion performance G=H89PβN/q952=0.16,H89p=3.5,H98y2=2.1 at βN～3,is achieved in this joint experiment.-The excellent confinement is associated with the formation of a large minor radius(p=0.6～0.7)internal transport barrier(ITB).The effects of ITB on improving plasma confinement are carefully analysed.However,the high confinement is terminated by an edge localized mode(ELM)trigged 4kHz m=4/n=1 MHD mode.Simulation results show it may be a resistive interchange mode or an infernal mode.Two possible methods are proposed to stabilize the MHD mode. |
