The Study Of Beam Injected Fast Ions Loss On EAST

Neutral beam injection is a primary auxiliary heating method on magnetic confinement fusion machine,the injected beam ions can effectively increase the plasma temperature,make plasma with hot component easier to abstain ignitio-Confinement of energetic particle in such a complex magnetic configuration and with such a lot of instabilities plasma has always been the focus of fusion research-The thesis analyzed the beam ions prompt loss,ripple loss,beam ions kinetic influence on MHD instability and induced loss based on EAST experiment,this work gives a solid reference for experiment operation and further understanding of the energetic particle physics.The thesis gives a full and accurate beam deposition based on EAST parameter,with beam birth deposition of four independent ion source,it has calculated prompt loss of co and counter current beam line,the loss fraction of counter injection is much larger than co injection,perpendicular larger than tangential.The reason arise from that radial position of primary neutral beam ionization located at low field side,co-injected beam ions will drift inward after birth at the initial magnetic flux surface,counter inject beam ion will stay outside of their birth magnetic flux surface.The orbit width of trapped particle is much larger than passing particle’s.The thesis analysis the possibility of toroidal field ripple well induced loss and collision’s influence on ripple stochastic diffusion,the parameter calculation of the shot analyzed show the ripple banana diffusion in low collisionality is the primary loss channel on EAST.The work calculated the beam ion ripple loss fraction and loss position with slowing down particle distribution of four independent beam injectors,the loss fraction of co beam line is lower than counter injection,particle’s loss position is at the below direction at the outer mid-plane of low field side due to direction of gradient magnetic field.The most effective method to decrease prompt loss and ripple are to increase plasma current provided no large scale MHD instability and optimize the plasma density profile,which almost determine the beam deposition profile with neutral beam stopping reactions.In numerous instabilities of tokamak,the thesis focuses on fishbones and sawtooth which often appears during beam heating plasma discharges,the work gives an approximation analysis for internal kink mode dispersion relation with basic properties.For more accurate numerical calculation in beam heating plasma experiment analysis,the thesis gives perturbative analysis and linear solutions,the thesis calculate the internal kink mode structure,MHD potential energy and beam ion kinetic contribution,get the mode growth evolution as a function of beam betahot.The fishbone threshold betahot is about 6.8*10^-3 at the plasma center,this is also the stable regime for fishbone and sawtooth.In order to explore other stable regime under the present EAST NBI layout,the thesis also investigate a case with co-current injection plus counter injection,the stable regime for normalized beam betahot threshold is 9.1*10^-3 at the plasma center.The thesis found fast ion distribution have a strong stabilization on sawtooth branch,this is consistent with EAST experiment that sawtooth period is larger during beam heating plasmas.Monster sawtooth is too dangerous for plasma confinement and impurity accumulation,so,the advice from this thesis is that the beam injection should be modulated on EAST with co and counter beam line at same time,at which period should be less than energy confinement time.For fishbone induced beam ion loss,we have used simplified fishbone model in TRANSP/NUBEAM and guiding center following code ORBIT,with mode amplitude measured 5.4a*10^-3 of n=1,m=1,the loss fraction is about 10%,lost particle’s energy range is 20-45keV,fishbone period～0.95 ms from analysis,the loss fraction is agree with the result reduced form neutron flux signals,this work give a valuable information for experiment operation.At the same time,the conceptual design of CFETR has been carrying out very well,in order to give a self-consistent calculation of fast ion loss in fusion reactor,the thesis studied the particle distribution of off-axis NBI and DT fusion reaction,within the larger version of the machine,ripple loss of these energetic particle’s ripple loss has been investigated,results show ripple loss fraction of DT alphas is larger than beam ions,the reason is the difference of fast ion distribution in phase space.The thesis analyzed the influence of collision on fast ion ripple in reactor parameter,result show the collisionless stochastic diffusion is the primary ripple loss channel.At the same time,the thesis gives a preliminary calculation about MHD induced fast ion loss with a reversed sheer equilibrium on CFETR,this work gives a valid foundation for further study of conceptual design.