WEKO3
アイテム
Simulation Study of Energetic Particle Driven Alfvén Eigenmodes and Geodesic Acoustic Modes in Toroidal Plasmas
https://ir.soken.ac.jp/records/3578
https://ir.soken.ac.jp/records/3578b93c00d004fd456aa6326238f09215d8
名前 / ファイル  ライセンス  アクション 

要旨・審査要旨 (320.0 kB)


本文 (7.4 MB)

Item type  学位論文 / Thesis or Dissertation(1)  

公開日  20130610  
タイトル  
タイトル  Simulation Study of Energetic Particle Driven Alfvén Eigenmodes and Geodesic Acoustic Modes in Toroidal Plasmas  
タイトル  
タイトル  Simulation Study of Energetic Particle Driven Alfvén Eigenmodes and Geodesic Acoustic Modes in Toroidal Plasmas  
言語  en  
言語  
言語  eng  
資源タイプ  
資源タイプ識別子  http://purl.org/coar/resource_type/c_46ec  
資源タイプ  thesis  
著者名 
王, 〓
× 王, 〓 

フリガナ 
ワン, ハオ
× ワン, ハオ 

著者 
WANG, Hao
× WANG, Hao 

学位授与機関  
学位授与機関名  総合研究大学院大学  
学位名  
学位名  博士（学術）  
学位記番号  
内容記述タイプ  Other  
内容記述  総研大甲第1545号  
研究科  
値  物理科学研究科  
専攻  
値  10 核融合科学専攻  
学位授与年月日  
学位授与年月日  20120928  
学位授与年度  
値  2012  
要旨  
内容記述タイプ  Other  
内容記述  Energetic particle driven instabilities are important issues for fusion plasmas because they lead to energetic particle transport and losses. Especially for fusion burning plasmas, where the getic alpha particles play the leading role in the fuel plasma heating, the energetic particle driven instabilities should be suppressed or mitigated for the better confinement of the energetic alpha particles. Then, the understanding of the fundamental properties of energetic particle driven instabilities will contribute to the successful operation of the future fusion reactors. In this dissertation, the linear properties and the nonlinear evolution of energetic particle driven Alfvén eigenmodes and geodesic acoustic modes (GAM) are investigated using a hybrid simulation code for magnetohydrodynamics (MHD) and energetic particles. The interaction between energetic particles and Alfvén eigenmodes in reversed shear tokamak plasmas are investigated for different minimum safetyfactor values. When the energetic particle distribution is isotropic in velocity space, it is demonstrated that the transition from lowfrequency reversed shear Alfvén eigenmode (RSAE mode) to toroidal Alfvén eigenmode (TAE mode) takes place as the minimum safetyfactor value decreases. The frequency rises up from a level above the GAM frequency to the TAE frequency. It is found that the energetic particles both co and countergoing to the plasma current are transported by the TAE mode, whereas the cogoing particles are primarily transported by the lowfrequency RSAE mode. When only the copassing particles are retained, the lowfrequency RSAE modes are primarily destabilized. On the other hand, the highfrequency RSAE modes are destabilized when only the counterpassing particles are retained. The linear properties and the nonlinear evolution of energetic particle driven GAM (EGAM) are explored for the Large Helical Device (LHD) plasmas. Since the kinetic GAM frequency in LHD is close to that in tokamaks, tokamak type equilibria are examined with concentric magnetic surfaces, and with the safety factor profiles and the aspect ratio similar to the LHD plasmas. For the linear properties, it is found that the EGAM is a global mode because the fluctuation frequency is spatially constant, whereas the conventional local GAM frequency constitutes a continuous spectrum that varies depending on the plasma temperature and the safetyfactor. The frequency of the EGAM intersects with the GAM continuous spectrum. The EGAM frequency is lower for the higher energetic particle pressure. The poloidal mode numbers of poloidal velocity fluctuation, plasma density fluctuation, and magnetic fluctuation are m=0, 1, and 2, respectively. Good agreement is found between the LHD experiment and the simulation result in the EGAM frequency and the mode numbers. The EGAM spatial profile depends on the energetic particle spatial distribution and the equilibrium magnetic shear. The wider energetic particle spatial profile broadens the EGAM spatial profile. The EGAM spatial profile is wider for the reversed magnetic shear than for the normal shear. The nonlinear evolution of EGAM is studied using the hybrid simulation code. The frequency chirping of EGAM has been observed in LHD and tokamaks. The frequency chirping up and down is found to take place in the simulation results. In order to understand the physics mechanism of the frequency chirping, the energetic particle distribution function and the energy transfer rate from the particles to the wave are analyzed in 2dimensional velocity space of energy and pitch angle variable. In the linearly growing phase of the instability, two resonant regions, one destabilizing and the other stabilizing the EGAM, are found in the velocity space. In the nonlinearly frequency chirping phase, a pair of hole and clump is created at each resonant region. A hole and a clump correspond to negative and positive fluctuation, respectively in the distribution function. Then, two pairs of hole and clump are created, one at the destabilizing region and the other at the stabilizing region. The transit frequencies of the holes and clumps are compared with the EGAM frequency. The transit frequencies of the holes and clumps are in good agreement with the two branches of the EGAM frequency, one chirping up and the other chirping down. This indicates that the holes and clumps are kept resonant with the EGAM and the frequency chirping can be attributed to the holeclump pair creation. The holeclump pair creation and the associated frequency chirping are known to take place when the system is close to the instability threshold for the inverse Landau damping. However, the direct numerical simulations have so far been limited to the holeclump pair creation at the destabilizing region in 1dimensional velocity space. The result presented in this dissertation is the first numerical demonstration of a) holeclump pair creation and frequency chirping for EGAM, b) two pairs creation at the destabilizing and the stabilizing regions, and c) holeclump pairs in 2dimensional velocity space. For the linear properties, it is found that the EGAM is a global mode because the fluctuation frequency is spatially constant, whereas the conventional local GAM frequency constitutes a continuous spectrum that varies depending on the plasma temperature and the safetyfactor. The frequency of the EGAM intersects with the GAM continuous spectrum. The EGAM frequency is lower for the higher energetic particle pressure. The poloidal mode numbers of poloidal velocity fluctuation, plasma density fluctuation, and magnetic fluctuation are m=0, 1, and 2, respectively. Good greement is found between the LHD experiment and the simulation result in the EGAM frequency and the mode numbers. The EGAM spatial profile depends on the energetic particle spatial distribution and the equilibrium magnetic shear. The wider energetic particle spatial profile broadens the EGAM spatial profile. The EGAM spatial profile is wider for the reversed magnetic shear than for the normal shear. The nonlinear evolution of EGAM is studied using the hybrid simulation code. The frequency chirping of EGAM has been observed in LHD and tokamaks. The frequency chirping up and down is found to take place in the simulation results. In order to understand the physics mechanism of the frequency chirping, the energetic particle distribution function and the energy transfer rate from the particles to the wave are analyzed in 2dimensional velocity space of energy and pitch angle variable. In the linearly growing phase of the instability, two resonant regions, one destabilizing and the other stabilizing the EGAM, are found in the velocity space. In the nonlinearly frequency chirping phase, a pair of hole and clump is created at each resonant region. A hole and a clump correspond to negative and positive fluctuation, respectively in the distribution function. Then, two pairs of hole and clump are created, one at the destabilizing region and the other at the stabilizing region. The transit frequencies of the holes and clumps are compared with the EGAM frequency. The transit frequencies of the holes and clumps are in good agreement with the two branches of the EGAM frequency, one chirping up and the other chirping down. This indicates that the holes and clumps are kept resonant with the EGAM and the frequency chirping can be attributed to the holeclump pair creation. The holeclump pair creation and the associated frequency chirping are known to take place when the system is close to the instability threshold for the inverse Landau damping. However, the direct numerical simulations have so far been limited to the holeclump pair creation at the destabilizing region in 1dimensional velocity space. The result presented in this dissertation is the first numerical demonstration of a) holeclump pair creation and frequency chirping for EGAM, b) two pairs creation at the destabilizing and the stabilizing regions, and c) holeclump pairs in 2dimensional velocity space. 

所蔵  
値  有 