Energy confinement scaling in the low aspect ratio National Spherical Torus Experiment (NSTX)
Energy confinement scaling in the low aspect ratio National Spherical Torus Experiment (NSTX)
复制标题
低纵横比国家球形环面实验 (NSTX) 中的能量约束缩放
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
S. Sabbagh
中科院分区：
文献类型：
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作者：
S. Kaye;M. Bell;R. Bell;E. Fredrickson;B. LeBlanc;K. Lee;S. Lynch;S. Sabbagh
为了了解在高功率国家球面环面实验放电中低长径比下的全局约束时间和热能约束时间的参数依赖性，进行了系统和统计研究。L模和h模放电的全局约束时间和热约束时间都可以超过常规长径比的h模标度给出的值。在h模式下的系统扫描结果表明，约束时间与等离子体电流呈近似线性关系，并且功率衰减比在常规宽高比下观察到的要弱。此外，对环形磁场的依赖比传统的长径比托卡马克更强。后一种趋势在可用数据集的统计分析中也很明显。这些统计研究还表明，由于预测变量之间的相关性，与系统扫描相比，对等离子体电流的参数依赖性较弱。基于工程变量的回归，当转换为无因次物理变量时，表明τ e对βt的依赖可以从负到零。直接基于无量纲物理变量的回归是不精确的，因为这些变量之间存在很大的相关性。在其他固定的操作参数下，约束数据中的散射是由于ELM活动、低频密度波动和等离子体成形的变化造成的。
Systematic and statistical studies have been conducted in order to develop an understanding of the parametric dependences of both the global and thermal energy confinement times at low aspect ratio in high power National Spherical Torus Experiment discharges. The global and thermal confinement times of both L- and H-mode discharges can exceed values given by H-mode scalings developed for conventional aspect ratio. Results of systematic scans in the H-mode indicate that the confinement times exhibit a nearly linear dependence on plasma current and a power degradation weaker than that observed at conventional aspect ratio. In addition, the dependence on the toroidal magnetic field is stronger than that seen in conventional aspect ratio tokamaks. This latter trend is also evident in statistical analyses of the available dataset. These statistical studies also indicate a weaker parametric dependence on plasma current than found in the systematic scans, due to correlations among the predictor variables. Regressions based on engineering variables, when transformed to dimensionless physics variables, indicate that the dependence of BτE on βt can range from being negative to null. Regressions based directly on the dimensionless physics variables are inexact because of large correlations among these variables. Scatter in the confinement data, at otherwise fixed operating parameters, is found to be due to variations in ELM activity, low frequency density fluctuations and plasma shaping.