Measurement Of Intrinsic Torque Using The Balanced Neutral Beam Injection On EAST

Plasma rotation is widely considered to be important for improving MHD stability and confinement in tokamak plasmas.In tokamak devices-Experimental Advanced Superconducting Tokamak(EAST),rotation is primarily driven by neutral beam injection(NBI).However,neutral beams are difficult to efficiently drive a large rotational speed due to the large plasma volume and high density in ITER and future fusion reactor plasmas,.In previous experimental studies,the rotation has been found in many devices without the external direct momentum injection.This kind of intrinsic rotation driven by plasma stress independent of external momentum is closely related to plasma density,temperature,pressure and energy storage,which may be the key to solve the problem of rotation velocity on the future reactor.The driving mechanism of intrinsic rotation has become a research hotspot issues.In this paper,co-and counter-current neutral beams on EAST are modulated to balance the intrinsic and externally injected torques,which result in the rotation profile close to zero and flat.With ignoring the diffusion and pinch term in the angular momentum balance equation,intrinsic torque can be determined by the torque of NBI.By this way,the profile of intrinsic torque was measured experimentally for the first time on EAST.The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction,peaked in the plasma edge and negligibly small in the core.The intrinsic torques under different discharge conditions were measured.Comparing the intrinsic torque measured under the condition of different parameters,intrinsic torque was found strongly depends on the normalized gyroradius and collissonality,the core of intrinsic torque decrease with normalized gyroradius increase,and increases with the increase of normalized collissonality.