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An examination of the effects of neutral particles on the edge plasma in Tokamaks.

机译：检查托卡马克中性粒子对边缘等离子体的影响。

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摘要

The recycling of neutral atoms in the plasma edge is an area of increasing interest in Tokamak plasma physics. Strong evidence has been presented recently that suggests there is a strong link between neutral particles and the overall confinement of the plasma. Experimental studies of neutral particle dynamics [1] and penetration into the core plasma [2] have stimulated investigations of the effects of neutrals upon edge phenomena such as MARFEs [3, 4] (Multifaceted Axisymmetric Radiation from the Edge), the L-H (Low-to-High Mode) transition [5--7], the structure of the edge pedestal [8, 9] in H-mode plasmas, and the interpretation of thermal transport coefficients from measurements of edge density and temperature gradients [10]. One such piece of evidence (and major motivation for our research) comes from a series of experiments carried out on the Tokamak TEXTOR that qualitatively demonstrates there is a direct link between density limits and neutral particle density in the plasma edge. The details of this experiment are found in Chapter 2 of this thesis.;Many studies have focused on the investigation of edge pedestal fueling by neutrals produced from ions recycling from edge plasma material surfaces. At issue is whether the edge pedestal is fueled primarily by neutrals recycling from ion fluxes incident on the divertor target plates, as has long been assumed, or by neutrals recycling from the main plasma chamber wall produced by radial convective ion fluxes in the SOL (scrape-off layer). Evidence for both divertor recycling [11, 12] and main chamber recycling [13--15] stimulated an extensive data collection, analysis and modeling effort for a series of DIII-D discharges [16], which concluded that divertor recycling was the primary fueling mechanism in DIII-D.;One purpose of this thesis is to make use of this extensive data compilation/analysis and background plasma calculation database that has been established for this series of DIII-D discharges for a detailed analysis of neutral particle recycling and edge pedestal fueling in an H-mode Tokamak plasma with the 2D neutral particle transport code GTNEUT [17, 18]. We have chosen the deterministic GTNEUT code instead of the more familiar Monte Carlo codes such as DEGAS2 [19] and EIRENE [20] which are frequently used with plasma fluid codes such as SOLPS [21] and UEDGE [22] for neutral recycling calculations in Tokamak plasmas because of the difficulty of obtaining sufficiently good statistics to calculate accurate neutral profiles with Monte Carlo (see e.g. Fig. 17 in Ref. [21]). The GTNEUT code is discussed in detail in Chapters 3 and 4. The ion flux measurements used in this analysis are discussed in Chapter 5. The neutral particle recycling and pedestal fueling calculations are discussed in Chapter 6. Analyses of the relative importance of neutrals recycled at different spatial locations and discussion of the calculational uncertainties are also presented in Chapter 6. Suggestions for improvements to the GTNEUT code are briefly discussed in Chapter 7. A brief summary and conclusions are presented in Chapter 8.
机译：等离子体边缘中的中性原子的循环利用是托卡马克等离子体物理领域日益关注的领域。最近已经有强有力的证据表明，中性粒子与等离子体的整体限制之间存在着很强的联系。中性粒子动力学[1]和渗透到核心等离子体中的实验[2]的实验研究促进了中性粒子对边缘现象（例如MARFE [3，4]（来自边缘的多轴对称辐射），LH（低）的边缘现象）的影响的研究。 -高模式）转换[5--7]，H模式等离子体中的边缘基座[8，9]的结构，以及通过测量边缘密度和温度梯度[10]来解释热传递系数。这样的证据（也是我们研究的主要动力）来自于Tokamak TEXTOR上进行的一系列实验，定性地证明了密度极限与等离子体边缘中性粒子密度之间存在直接联系。该实验的详细信息可在本文的第二章中找到。许多研究集中在研究边缘等离子体材料表面的离子回收产生的中性粒子对边缘基座的供能方面。有争议的是，边缘基座是否主要是由入射到偏滤器靶板上的离子流中的中性物质再循环（如长期以来假设的那样）提供燃料，还是由SOL中径向对流离子流所产生的主等离子体室壁的中性物质再循环提供燃料（刮擦） -off层）。偏滤器再循环[11，12]和主腔室再循环[13--15]的证据刺激了一系列DIII-D排放物[16]的大量数据收集，分析和建模工作，得出结论，偏滤器再循环是主要的本论文的目的之一是利用为该系列DIII-D放电建立的广泛的数据汇编/分析和背景等离子体计算数据库，对中性颗粒的再循环和排放进行详细分析。在H模式Tokamak等离子体中使用2D中性粒子传输代码GTNEUT [17，18]为边缘基座加油。我们选择了确定性的GTNEUT代码，而不是更熟悉的蒙特卡洛代码（例如DEGAS2 [19]和EIRENE [20]），这些代码经常与等离子流体代码（例如SOLPS [21]和UEDGE [22]）一起用于中性回收计算。托卡马克等离子体由于难以获得足够好的统计数据来利用蒙特卡洛方法来计算准确的中性分布（例如参见参考文献[21]中的图17）。在第3章和第4章中将详细讨论GTNEUT代码。在第5章中将讨论此分析中使用的离子通量测量。第6章中将讨论中性粒子再循环和基座加油计算。第6章还介绍了不同的空间位置，并对计算不确定性进行了讨论。第7章简要讨论了改进GTNEUT代码的建议。第8章给出了简短的摘要和结论。

著录项

  • 作者

    Friis, Zachary Ward.;

  • 作者单位

    Georgia Institute of Technology.;

  • 授予单位 Georgia Institute of Technology.;
  • 学科 Engineering Nuclear.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 234 p.
  • 总页数 234
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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