Investigation On Key Aspects Of Heat Load On Divertor Target Plates In Tokamak Different Confinement Modes

Divertor is a crucial component of advanced tokamaks,playing a significant role in the research of tokamak physics and magnetic confinement fusion energy.The primary function of the divertor configuration is to“guide”the heat flow and particles discharged from the core towards the target along the magnetic field lines after entering the open field line area.Consequently,the divertor configuration not only protects the first wall but also mitigates the impact of the interaction between the plasma and the limiter surface in the limiter configuration on the core plasma.However,while the divertor configuration safeguards the first wall,it simultaneously elevates the heat load on the divertor target plate.In particular,the instantaneous high heat load induced by edge-localized mode（ELM）explosions may significantly surpass the threshold that the target material can tolerate,leading to sputtering,etching,and melting of the target surface.As such,devising strategies to minimize the heat load on the divertor target plate and reduce its sputtering is a pivotal and challenging task in current tokamak research.This thesis will concentrateon the heat load of the divertor target plate,employing the numerical simulation（SOLPS-ITER）to investigate and analyze the impact of impurity particle injection downstream and various confinement modes of the upstream on the target plate’s heat load,and furthermore,the study will analyze the effect of magnetic field strength on the generation of high heat flux at the target plate within the linear configuration device.In the downstream region,this thesis investigate and analyze the impact of impurity particle injection on the thermal load of the divertor target plate.In both the L-and H modes,impurity particles are injected at different positions and their effects on upstream plasma density and temperature profile,upstream impurity particle distribution,down-stream electron temperature,and heat flux are discussed and analyzed.Additionally,based on the different distributions,the energy radiation of impurity particles in the divertor area at various positions is further examined.Utilizing the momentum equation including impurity particles,the diffusion mechanism of impurity particles in the divertor and SOL region is also preliminarily analyzed.The simulation results demonstrate that impurity particle injection can effectively reduce the heat load of the divertor target plate under the two confinement modes.Furthermore,the injection position of impurity particles has a remarkable influence on the distribution of upstream and downstream impurity particles,the radiation density of different regions of impurity particles,and the target detachment threshold.In the upstream region,this thesis examine and analyze the influence of different confinement modes on the thermal load of the divertor target plate.Based on the ex-perimental data of the EAST H-mode and I-mode,the effect of the confinement mode on the downstream plasma distribution,as well as the electron temperature and heat flux of the target plate is discussed,and the underlying physical mechanism is explored.By scanning the density at the upstream interface,the detachment threshold of the upstream density of the divertor under different confinement modes is ascertained.Starting from two relatively extreme upstream conditions（low and high upstream density）,the influ-ence of the confinement mode on the upstream and downstream plasma parameters is analyzed and discussed.Then,impurity gas puffing in I-mode is investigated to evaluate its effect on target heat load.Finally,the heat flux,energy density inside and outside the separatrix,and plasma pressure is analyzed and discussed by’two-point’model.The simulation results demonstrate that detachment threshold of the I-mode is lower than that of the H-mode.Furthermore,under the same upstream density conditions,the I-mode has an upstream electron temperature closer to that of H-mode,and lower target electron temperature and heat flux.Results also shows that impurity can effectively reduce heat flux and cause less pollution to the core plasma.At the divertor target plate,it is challenging to generate heat flux that meets the future tokamak target plate requirements within current tokamak parameter limitations.This thesis compares the linear plasma device to the SOL and divertor to discuss and study the high heat flux that fulfills the ITER requirements.It begins with the physical model and examines the similarities and differences between the SOL and the physical model of the linear plasma device.Utilizing the linear plasma device of Harbin Institute of Technology,the magnetic field distribution,plasma source distribution,and other relevant parameters are calculated,and the simulation linear plasma device module id developed in SOLPS-ITER,enabling the successful simulation of the steady-state discharge process of the linear plasma device.Focusing on the analysis of the influence of the magnetic field strength on the heat flux of the target plate in the linear device,the simulation results demonstrate that a strong magnetic field can better confine the plasma and,under such conditions（≈2 T）,the HIT linear plasma device can attain a heat flux that meets the requirements(>10 MW·m^-2)on the target plate.