DIII-D plasmas are compared for two upper divertor configurations: with the outer strike point on the small angle slot (SAS) divertor target and with the outer strike point on the horizontal divertor target (HT). Scanning the vertical distance between the magnetic null point and the divertor target over a range 0.10–0.16 m is shown to increase the threshold power, Pth , and edge plasma power, PLoss , for the low-to-high confinement (L–H) and H–L transitions respectively, by up to a factor of 1.4. The X-point height scans were performed at three L-mode core plasma line average electron densities, n¯e= 1.2, 2.2 and 3.6 ×1019m−3 , to investigate the density dependence of divertor magnetic configuration influence on Pth . The X-point height, Zx-pt , was further extended across the range 0.16–0.22 m with the more open HT divertor configuration, for which a clear decrease in Pth with increasing Zx-pt is observed. The dependence of Pth on divertor magnetic geometry is further investigated using a time-dependent probability density function (PDF) model and information geometry to elucidate the roles played by pedestal plasma turbulence and perpendicular velocity flows. The degree of stochasticity of the plasma turbulence is observed to be sensitive to the plasma heating rate. The calculated square of the information rate shows changes in the relative density fluctuations and perpendicular velocity PDFs begin 2–5 ms prior to the L–H transition for three plasmas; providing a crucial measurement of the dynamic timescale of external transport barrier formation. Additionally, both information length and rate provide potential predictors of the L–H transition for these plasmas.

中文翻译：

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磁偏滤器配置对H模式转变影响的统计分析

比较了两种上部偏滤器配置的 DIII-D 等离子体：外撞击点位于小角度槽 (SAS) 偏滤器目标上，外撞击点位于水平偏滤器目标 (HT) 上。在 0.10-0.16 m 范围内扫描磁零点和偏滤器目标之间的垂直距离可增加阈值功率， 磷th 和边缘等离子体功率， 磷损失 ，分别针对从低到高限制 (L–H) 和 H–L 转变，最高可达 1.4 倍。 X点高度扫描是在三个L模式核心等离子体线平均电子密度下进行的， n￣e= 1.2、2.2 和 3.6 ×1019米-3 ，研究偏滤器磁配置影响的密度依赖性 磷th 。 X 点高度， Zx-点 ，通过更开放的 HT 偏滤器配置，进一步扩展到 0.16–0.22 m 的范围，从而明显降低 磷th 随着增加 Zx-点 被观察到。的依赖性 磷th 使用瞬态概率密度函数（PDF）模型和信息几何进一步研究了偏滤器磁几何形状，以阐明基座等离子体湍流和垂直速度流所发挥的作用。观察到等离子体湍流的随机程度对等离子体加热速率敏感。计算出的信息率平方显示了三种等离子体在 L-H 转变之前 2-5 毫秒开始的相对密度波动和垂直速度 PDF 的变化；提供外部传输障碍形成的动态时间尺度的关键测量。此外，信息长度和速率都为这些等离子体的 L-H 转变提供了潜在的预测因子。