Research Of Alfven Waves In EAST And Active Control Of Alfven Waves In D?-D Tokamak

Tokamak is one kind of fusion research device.In tokamaks the burning plasmas undergo fusion reactions.The fusion reactions generate a lot of high energy alpha particles,besides,external heating including lower hybrid wave heating,electron cyclotron heating,ion cyclotron heating and neutral beam injection also introduces large amount of high energy electrons and ions into plasma where 'high energy' is relative to the temperature of background plasma.These energetic particles can drive one of the basic eigenmodes of plasma,named Alfven eigenmodes?AEs?.AEs in turn is able to influence the orbits and confinement of energetic particles.Therefore,it is of significance to investigate the interaction between energetic particles and AEs.As the generation of AEs in future fusion reactors is unavoidable,to control AEs at a desirable level is also important.The research work of this thesis is carried out in EAST and D?-D tokamaks.It is the first research of Alfven eigenmodes driven by fast electrons heated by lower hybrid wave in the steady-state long pulse discharge of EAST.And a feedback control system is firstly built in D?-D tokamak:?1?Study the AEs in EAST tokamak under the condition of lower hybrid heating,[?]Through analysis of discharges from 2015 to 2016 using magnetic probes,many discharges have perturbation modes of frequency 100-450 kHz.When looking at single discharge,the modes frequency involves proportional inversely to the square root of plasma density and the safety factor,f? 1/???and f? 1/q95.When looking at a series of discharges,it is found that f? vA/?4?q95?,where vA is the Alfven speed.The above characteristics show that the observed modes are Alfven eigenmodes.[?]GTAW calculated Alfven continuum gaps tell that these modes are located at TAE and EAE gaps.[?]The ray-tracing code GENRAY-CQL3D calculates the fast electrons distribution function and LHW heating power deposition profile.The results imply that the passing electrons,barely-trapped electrons and trapped electrons of energy 12-300 keV can resonant with the modes.The non-uniform deposition of LHW heating power causes the population inversion of fast electrons which provides free energy that drives the modes unstable.[?]Finally,the statistical results of a few hundred discharges show that AEs are mostly likely to appear when the LHW power is above 1 MW and the plasma density is below 3 × 10¹9 m⁽-3.?2?Active real-time control of AEs in DI?-D tokamak.Through real-time ECE diagnostic systems the AEs amplitude and frequency from edge to the center of plasma can be detected in real time.Based on this an AE control system is newly built in the D?-D plasma control system?PCS?.By testing different actuators of AE controller,the control experiments are divided into two parts:[?]open-loop and feedback control of AEs amplitude by NBI and[?]open-loop control of AEs by ECH.The test results of part[?]shows that in the feedback control loop by varying NBI power between 0-8 MW the AE amplitude is modulated to the target values,which indicates that NBI can be one of the candidate actuators of AE controller in future fusion reactors.The results of part[?]demonstrate that injecting ECH near qmin is effective in modulating AE's behavior,but compared with NBI,the physical evolution of AE is much more complicated.Before ECH becomes an actuator in the feedback loop,more experiments are needed to explore the control model.For both[?]and[?],the ratio between the TRANSP calculated neutron rate and the measured neutron rate follows the AEs amplitude closely in experiments,verifying that this ratio can be another sensor for the control system.This latter will be te.sted in the ne.ar future with the.implementation of models that can calculate the?classically?expected neutron rate in real time.This thesis has also tried to calculate the neutron rate by a zero-dimentional model.But the result is not as precise as the classical value calculated by TRANSP,thus,a more precise and simultaneously fast enough model is needed to meet the control demands.The thesis lastly discusses a few problems that is actively studied in current energetic particle research area,for example,the nonlinear physics of energetic particles and AE activity in steady state scenario.Some future upgrading thoughts of AE controller are presented,such as?a?neural network or reduced model for real-time neutrons production calculation,?b?new actuator for AE,like neutral beam voltage variation,and?c?AE control test at steady state plasma.