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研究生: 黃柏慈
HUANG, BOTSZ
論文名稱: 以GPU模擬阿伐粒子在背景亂流中的漂移
Fusion born alpha particle drift simulation with background turbulence by GPU computing
指導教授: 西村泰太郎
Yasutaro Nishimura
學位類別: 碩士
Master
系所名稱: 理學院 - 太空天文與電漿科學研究所
Institute of Space, Astrophysical and Plasma Sciences(ISAPS)
論文出版年: 2013
畢業學年度: 101
語文別: 英文
論文頁數: 46
中文關鍵詞: 阿伐粒子漂移波亂流GPU平行計算
外文關鍵詞: Alpha particle, drift-wave turbulence,, GPU parallel computation
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  • 本研究討論核融合阿伐粒子在漂移波背景亂流下的漂移行為。本模型以粒子迴旋中心運動與漂移波檢驗在背景亂流下第二不變量是
    否依然成立。藉此模型,粒子的參數和背景亂流的結構都是可以被直接操控,例如可改變粒子的能量與亂流的結構。在解析工作部分發現 island 大小與粒子平行磁力線的速度相關,且 island 的位置與 ${omega}_{star} / V_{parallel}$ 有關。統計數據的結果與解析工作吻合。數值模擬則指出第二不變量不意因漂移波的擾動而被否決。然而,在鄰近 banana tips 的區域,卻因為粒子動能趨近於零而對背景亂流相對敏感。該數值分析工作運行於 GPU 之平行運算上以有效減少計算資源與時間。

    This thesis investigates the fusion born alpha particle behavior in the presence of drift wave turbulence in toroidal geometry. We employed the guiding center motion and ballooning type drift wave as simulation model to examine the conservation of second adiabatic invariant. By the orbit-following code, we are able to control the parameter of particle and turbulence structure, e.g. particle energy and turbulence amplitude. In the analytical work , we found that parallel velocity is related to island width and the shift of island is proportional to ${omega}_{star}/V_{parallel}$. The statistical result is consistent with analytical work. In numerical work, for trapped particles, the second adiabatic does not easily break. Furthermore, the banana tip is sensitive to $E imes B$ drift since the $V_{parallel}$ is near zero. These numerical work are demonstrated by GPU's parallel computation , we can effectively reduce computation time and resource.

    Introduction 3 2 Simulation Model 5 2.1 Derivation of guiding center equation ....... 5 2.2 The electric field by a ballooning eigenmode structure. 8 2.3 Guiding center equation in flux coordinate ......... 10 3 Theoretical Analysis...................................13 3.1 Conservation of magnetic motment .............13 3.2 Action-angle variable and second adiabatic invariant J.15 3.3 Banana orbit in the absence of drift wave turbulence .17 3.4 The Kolmogorov-Arnol’d-Moser theorem .... 19 4 Particle simulation results 21 4.1 Particle motion without fluctuation; neoclasical transport...21 4.2 Passing particle motion in the presence of electrostatic fluctuation...22 4.3 Radial shift of islands due to finite ω⋆ effects . . .27 4.4 Overlapping criterion of electric islands; a Hamiltonian analysis ............................30 4.5 Diffusion of passing particles ...................34 4.6 Diffusion of trapped particles....................34 5 Summary and future work 39 A Methods of statistical analysis........................43 A.1 Derivation of cumulants ........................43 A.2 Method of least squares ........................ 45

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