Experimental Investigation Of Intrinsic Rotation Based On X-ray Imaging Crystal Spectrometer On J-TEXT Tokamak

As a magnetic confined fusion device, tokamak plasma should reach the required triplet for ignition. The macro and micro instabilities in tokamaks always exist, deteriorating the confinement and even stimulating a major disruption which can cause irreparable damage. The transition from L-to H-mode discharge motivates the research on plasma rotation. The plasma rotation increases greatly during the formation of internal transport barrier due to the suppression of turbulence. In addition, certain plasma rotation and its shear have positive effects in suppressing macroscopic instabilities and they are related to the threshold power for achieving H-mode. It is thus very important for tokamak researchers to monitor and control the plasma rotation.In present tokamaks, plasma rotation is usually driven by externally neutral beam injection system directly. Charge exchange and Coulomb collision happens between energetic neutrons and main ions which in turns transfers the momentum of neutrons to plasma. To ITER plasmas, the penetration depth and efficiency of neutral beams will be limited by its high density and big mass. Other driven mechanism should be considered for ITER which need certain rotation to suppress instabilities. However, the intrinsic rotation observed in tokamaks without any external momentum input can be a candidate for ITER. The intrinsic rotation in L-and H-mode has been investigated broadly:its transport along radial direction is anomalous, and it is found to be related to many plasma parameters. During the last several tens of years, there are still gaps between experimental observations and theoretical explanations. Even for the Ohmic plasma rotation, it is an open question to us. The investigation of basic Ohmic plasma rotation is being carried out on J-TEXT tokamak.A new x-ray imaging crystal spectrometer (XICS) has been developed for J-TEXT tokamak to measure the core rotation velocity. By injecting unperturbed argon into plasma, the XICS can obtain the Doppler shifted spectra of heliumlike argon. There is no external momentum input thus it is good for the investigation of intrinsic rotation. It can provide spatial and high temporal resolved (up to2ms) measurements of electron temperature (Te), ion temperature (Ti) and toroidal rotation. for J-TEXT Ohmic plasmas.Firstly, basic characteristics of J-TEXT Ohmic discharges have been analyzed by using theTe and Ti obtained from XICS. Based on existing rotation theory, the absolute wavelength of XICS has been calibrated by using locked mode discharge and oscillation frequency of sawtooth precursor. The rough profile of toroidal rotation is measured combining edge visible grating spectrometer. The evolution of rotation profile under the influence of externally applied magnetic perturbation field has been investigated on J-TEXT. It is found that only the resonant component makes effect on the rotation. When field penetration happens at q=2surface, the core and edge rotation increase towards co-Ip direction at nearly the same time. After penetration the rotation profile reachs a new steady state in a time scale similar to energy confinement time. The rotation transport from the q=2surface to core is too fast to be explained by only anomalous damping effect. Mode coupling between2/1mode and1/1mode is observed during penetration and it can provide electromagnetic force which should be the additional effect. However, the rotation profile still has radial gradient during mode coupling, this maybe explained by imcomplete coupling between1/1,2/2and2/1observed in soft x-ray array. Intrinsic rotation is also revealed in tearing mode frequency. In discharges with stable rotating tearing mode (TM), its responses to resonant magnetic perturbations (RMPs) can be devided into four cases:complete suppression of tearing mode, incomplete suppression, mode locking and non-uniform oscillation.The results are sensitive to the initial frequency of TM and amplitude of RMPs. The threshold for mode locking is linear with TM frequency, and when TM frequency is larger than5kHz mode suppression always happens first. The simulation results based on a set of reduced magnetohydrodynamic equations are consistent with the experimental observations.