| Edge turbulence is believed to be the key of tokamak confinement.The nonlinear interaction between turbulence and edge shear flows is one of the main mechanisms of turbulence suppression.This nonlinear process could transfer the energy from turbulence to shear flows.In early experimental research,by applying the zero-dimensional model,this process is nothing more than energy transfer.However this hypothesis is not applicable for localized measurement in experiments.By theoretical and experimental study of the interaction between turbulence and shear flows,besides the energy transfer,the nonlinear interaction includes the spacial redistribution of shear flows driven by Reynolds stress and turbulence spreading induced by nonlinear coupling between different modes for localized measurement as well.When considering the kinetic energy redistribution process of turbulence and shear flows,both energy budgets can be balanced.The ECRH power scanning experiments on the HL-2A tokamak shows that the energy transfer between one branch of the zonal flows,geodesic acoustic modes(GAMs)and turbulence,as well as the nonlinear growth rate of GAMs increases monotonically with ECRH power increasing.The Langmuir probe array is not suitable for experimental studies of turbulence energy balance in high-performance discharge with high auxiliary heating power.An advanced beam emission spectroscopy system is developed on HL-2A tokamak for turbulence measurement.By optimizing the optics design,using high-sensitive detectors and low-noise design of pre-amplifier,the BES system could achieve a high time resolution of 0.5 ?s,high spatial resolution of 1 cm radially and 1.5 cm poloidally,providing an advanced performance in the world.At present,16-channel(2×8)BES system has been installed on HL-2A tokamak,covering a range of r = 26 ~ 42 cm near outer middle plane.Thus it is able to provide data for turbulence energy balance and other studies like MHD instability and energetic particles. |
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