Experimental Studies Of Asymmetry Of Parallel Flow And Toroidal Rotation Driven By ECRH

Plasma rotation and its shear have been recognized as being critical to the suppression of the magnetohydrodynamic activities and the improvement of plasma confinement.Accurate measurements of the flow velocity are required for better interpretation of plasma rotation which is the support for the achievement of plasma with high confinement.In the thesis,first,the effect of energy dependent cross section on rotation velocity measure with Charge eXchange Recombination Spectroscopy(CXRS)is analyzed.Then,the application in high electron temperature Te,wavelength calibration and inversion of X-ray Crystal Spectrometer(XCS)are described.Next,the asymmetric parallel flow on Large Helical Device(LHD)investigated.Last,the characterization of the effect of electron cyclotron wave(ECW)on toroidal rotation in Experimental Advanced Superconducting Tokamak(EAST)L-mode discharges is summarized.One symmetric layout of poloidal CXRS is applied on LHD.Correction velocity Vcor due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout.A linear relationship between Vcor and Ti is observed.The impact of beam energy on Vcor/Ti of the carbon system and the hydrogen system is discovered based upon the linear relationship.Effective emission coefficient(Q)from Atomic Data and Analysis Structure(ADAS)is utilized to study the dependence of Vcor on Q.It is observed that the calculated ?v/Ti increases linearly with the increasing normalized effective emission coefficient((1/Q)dQ/dv).Experimental(1/Q)dQ/dv is obtained according to this observation,and comparison with different fractions of n=2 excited state is also discussed.The influence of different receivers(carbon and hydrogen)is also presented.The experimental(1/Q)dQ/dv from the carbon system decreases with beam energy decreasing when beam energy is less than 30 keV/amu.This tendency of(1/Q)dQ/dv at low beam energy indicates the existence of the contribution of n=2 excited state donors to the cross section.Compared with the calculation,it is found that the fraction of n=2 excited state donors is about 0.2%.For the application of XCS in high Te,a double-crystal assembly with similar Bragg angles attached on the same substrate is applied.The helium-like and hydrogen-like argon spectra are recorded by one detector simultaneously at the first time,which broadens Te range of the application of XCS.For the wavelength calibration,on the basis of the difference in Doppler shift of various wavelengths,the relationship between the relative Doppler shift and toroidal rotation V? is acquired according to the layout of XCS.The calibrated V? from XCS with different wavelengths is in consistence with the measurement from CXRS.For the inversion,a cubic spline function is used to describe the local plasma parameters and the line integrated parameters are calculated according to the line of sights.At last,the optimal local profiles are obtained by using the least square fitting between the calculated and measure line integrated parameters.Full flow structure is measured by CXRS on LHD.Inboard/outboard asymmetry of parallel flow is observed according to the full flow profile measurement.A linear relationship between the integrated flow asymmetry and the electric potential difference is obtained in different magnetic fields and configurations.Asymmetric component of parallel flow measured is compared with the asymmetric component of parallel flow calculated in the incompressibility condition of flow on the magnetic flux surface.The measured asymmetric flow is consistent with the calculation in the plasma with small toroidal torque input in the inward shifted configuration.However,the measured asymmetric flow is significantly smaller than that calculated for the plasma with large toroidal torque or in the outward shifted configuration.One possible candidate could be the radial transport due to anomalous perpendicular viscosity plus strongly poloidally asymmetric radial flow.Change of toroidal rotation ?V? induced by ECW injection has been observed on EAST.It is found that the response of toroidal rotation is similar for all possible ECW toroidal injection angles in Ohmic discharges.The core V? increases in the co-current direction together with the rise in Te and Ti.The profile of Te,Ti and ?V? gradually become peaked after ECW injection.In addition,?V? in the core increases with the ECW injection power.Different behaviors are observed when ECW is injected to the lower hybrid current drive(LHCD)target plasmas,where Te and ?V? profile become peaked,while Ti profile turns to be flat after ECW injection.Besides,a perturbation analysis technique is applied to investigate the momentum transport in the discharges with different ECW power deposition positions.A much stronger response of ?V? to ECW modulation is observed with on axis ECW.It is found that the perturbation of Te starts in the power deposition position and then propagates to other regions.However,the perturbation of V? is from the edge to the core.Furthermore,the response time of Te in the core is much shorter than that of V?.These results suggest that V? is not simply determined by the local Te.For the discharges with on-axis and off-axis ECW,the diffusive coefficients ?? are similar.In addition,an inward convection velocity Vpinch are observed for both cases,but Vpinch is much larger with on-axis ECW.