Experimental Investigation Of Beta-induced Alfv(?)n Eigenmode In The J-TEXT Tokamak

International Thermonuclear Experimental Reactor is being constructed for undercontrolled and sustainable D-T fusion reaction.α particles with high energy are generated and could heat plasma through Coulomb collisions for sustainability of burning plasmas。Wave-particle interaction between α particles,energetic particles and waves result in transmiting energy to waves and exciting of weakly damped Alfv(?)n Eigenmodes(AEs).Relatively AEs could exchange energy and momentum with energetic particles and alpha particles.Exchanging time scale is far less than relaxation time of alpha particles,so that self-heating is unable to sustain.Wave-particle interaction could also cause anomalous alpha particles and energetic particles transport,which could degrade the plasma performance.Expellanted energetic particles would damage first wall of the device.On the other hand,Alpha ash could resonant with low-frequency AEs and be ejected from plasma core region.The aim being to understand AEs,with a broader goal and realize the relevant drive and damping mechanisms are keys to success for ITER and future magnetic controlled fusion reactor.Experimental manifestation of Beta-induced Alfv(?)n Eigenmodes(short for BAEs)are been studied systematicly in J-TEXT and EAST tokamak。We explored two kinds of method as driving term,which are tearing mode(TM)and external applied Resonant Magnetic Perturbation(RMP)field system.We have found that free energy of RMP could drive BAE against damping mechnisams when the components of RMP strength is large enough on the corresponding resonant surface.If RMP strength exceed penetration threshold and generat a large enough magnetic island,MIAE(magnetic island induced Alfv(?)n Eigenmode)could be driven.When TM is the exciting mechanism,the width of island should in the threshold range.Base on these two kinds of exciting method,we conduct the properties of BAE and MIAE veraciously.We have found that BAE and MIAE are magnetic perturbation on radial direction with standing wave structure.When magnetic island is generated,the phase of perturbation is between the O point and X point of magnetic island.The phase of standing wave nodes are on the O point and X point of magnetic island.Because of coulping relation between BAE phase and magnetic island phase,we could measure the mode structure of BAE to gain the phase information of magnetic island.Frequency of BAE and MIAE is consistent with theory.Frequency of MIAE is dominanted by width of MIAE.Measurement frequency of MIAE is needed to diagnose the width of magnetic island.We utilize RMP system to research the exciting mechanism of BAE and MIAE.The results show that BAE is driven by free energy of RMP,meanwhile energy would transform between BAE and magnetic island.MIAE is driven by pressure gradient so as size of magnetic island is large enough to change the gradient of pressure on the separatrix.