Experimental Study Of Toroidal Rotation Induced By LHCD On EAST

In this dissertation,the development of the Charge eXchange Recombination Spectroscopy(CXRS)diagnostic system on EAST tokamak and experimental study of the effect of the lower hybrid current on ion toroidal rotation in EAST are investigated.The detailed description of the thesis work are as follows:A new CXRS diagnostic system,which is used for measuring profiles of impurity ion temperature and rotation,has been developed on EAST.The CXRS system is located at the D port of the EAST,and covers whole profile of the plasma(R=1 500-2370 mm)with a spatial time resolution of 10-20 mm(high field side to low field side)and time resolution of 30-50 ms.Several techniques have been developed to improve the calibration of the CXRS diagnostic.Except measurement with articulated flexible coordinate measuring arm when the vessel was accessible,the Doppler shift of neutral beam emission spectra without magnetic field was applied for spatial calibration.Besides,neon lamp and laser,wavelength of which is close to the measured charge exchanged spectra,were combined in wavelength calibration for spectrometer.To simulate the effect of the width of the injected beam on the CXRS measurement,the Simulation of Spectra(SOS)has been upgraded.The simulation shows that the width of the injected beam shows an effect on the measurement only when there is an inner temperature gradient(ITB).Co-exist of the the two-beam result in lower results in temperature and rotation measurement,and the effect can be ignored in the core region of the plasma,while up to 17%and 25%error are obtained in the edge temperature and rotation measurement.Besides,the effect of the Zeeman effect on the measurement is also simulated.It is shows that there is no obvious effect on rotation measurement and the effect on the temperature measurement depends on the strength of the magnetic.Using the experimental data observed by CXRS diagnostic system and a tangentially viewing X-ray imaging crystal spectrometer(XCS),rotation driven by lower hybrid current drive(LHCD)was studied on EAST.This study presented plasma rotation behaviors with LHCD injection.Typically,10-20 km/s co-current rotation change was observed regardless of the direction of the rotation before LHCD injection.The relationship between plasma parameters and rotation was also investigated,which indicated that rotation decreases with internal inductance(li)and increase with safety factor(q0).Hysteresis between rotation and Te plasma stored energy was observed,suggesting different response time between the electron heating and rotation acceleration by LHCD.Besides,rotation changes after LHCD evacuation faster than that after LHCD injection.Profiles of the rotation after the LHCD injection show that the change of the rotation arise from the region where LHCD deposited and then transport to the whole profile.And around the LHCD deposition area,the counter-rotation change was observed as soon as the injection of the LHCD and changed to co-rotation change with the injection of the LHCD.To further study the parametric dependence,several controlled experiments were performed.The research shows that the change magnitude of rotation induced by LHCD decreases with plasma current(Ip),plasma density and increase with LHCD power.A comparison between the rotation driven by 4.6G LHCD and 2.45G LHCD on EAST is also presented,in which higher frequency LHCD could induce more rotation change.Finally,a simple physical model for rotation driven by LHCD on EAST is presented based on the experimental observation:after the injection of the LHCD,the momentum of the wave is delivered to the electron though Landau damping,and then transmitted to ion though collision.It is a fast process,and the rotation was drives to change to counter-current direction.The injection of the LHCD will induce a positive radial electric field and flatten the plasma current profile,both of which evolve in a slower time scale.A positive radial electric field will be induced by the injection of the LHCD at the LHCD deposition region provides a co-current rotation drive force but the process evolves in a slower time scale.When the force induced by radial electric filed exceeds the force induced by the momentum injection of the LHCD,the rotation start to change to co-current direction around LHCD power deposition region and then the change of the rotation transfers to the whole profile through momentum transport.