Study Of Nonlinear Instabilities Driven By Energetic Particles In HL-2A Tokamak

Study of non-linear instabilities driven by energetic particles in toroidal magnetic confinement devices plays an important role in exploring the thermonuclear fusion reactor.On the one hand,they are considered as desirable channels for energy and momentum transfer from resonant fast ions to thermal plasmas.Besides,they can also provide valuable information about the key plasma parameters,which is important for future burning plasma.However,the consequences of wave-particle interactions may be undesirable.They may redistribute and eject a large fraction of energetic particles from core plasmas,subsequently damage on the first wall and degrade plasma confinement.In this paper,we focus on Alfven modes(BAEs,RSAEs and TAEs)with frequency chirping(?ms)and mode-mode couplings in HL-2A.As known,frequency shifts nonlinearly,from the linear eigen-frequency,as phase space holes and clumps move upward and downward respectively from original resonance region.The spectral analysis obtained by Mirnov probes and plasms parameters show that the AEs(TAEs and BAEs)with downward chirping will be obsvered when the density is lower.As for RSAEs,the sweeping of frequency depends on safety factor q.And in the details of amplitudes,we found phase-flip along with burst both in up-and down-sweeping RSAEs.Based on Berk-Breizman model,?f-COBBLES and BOT code are applied to symmetric TAEs,and both Krook and Fokker-Plank collision models are considered.Comparing the amplitude of perturbations between experimental observation and calculation,Fokker-Plank is better than Krook model in the study of TAEs with chirping.The ?f-COBBLES-Fokker-Plank collision model yields better qualitative and quantitative agreement.While BOT-Fokker-Plank collision model is limited to qualitative simulation.BOT code with Fokker-Plank and Krook models are applied in TAEs with downward and upward hooked chirping.Though we didn't get perfect simulation results,the results of Fokker-Plank model show a qualitative agreement with observed phenomena.On the critical condition,the diffusion effect dominates in the downward sweeping behavior,while drag effect is essential to strengthen the hole movement,leading to hole-hole interactions in phase space and upward chirping in frequency.In terms of mode-mode couplings in HL-2A,the Fourier bicoherence is applied in the study of HFCMs,comfirming the three wave interaction.Then Lissaj ous-curve can provide more information about phase,which may reveal complicated physical mechanisms.For the mode-mode coupling instabilities,Lissajous-curves show that when three waves are coupled,any two of them will be locked.Secondly,rKBMs triggered by SMBI are investigated.Lissajous-curve shows that the phase-lock indicates the correlation of frequency of two modes.While phase-slip and phase-flip may be relevant to energy transport between two coupling modes,future work may be carried out for verification.In toroidal magnetic fusion devices,fast-ion D-alpha diagnostic(FIDA)is a powerful method to obtain the fast ion feature.The fast ion characteristics(such as density,space distribution and distrubiton of enery)can be inferred from the Doppler shifted spectrum of Da light according to charge exchange recombination process between fast ions and probe beam.In this paper,the operating principles,design of optical path and wave calibration of FIDA systems both in HL-2A and EAST are introduced.Finally,the preliminary results of energy spectrum analysises which reflect the information of fast ions are presented.