ITPA全球H模数据库中分界面密度与面向等离子体部件材料对H模约束的影响
The effect of separatrix density and PFC material on H-mode confinement in the ITPA global H-mode database
AI总结：
本研究基于ITPA全球H模数据库，分析了分界面密度与PFC材料对H模约束的影响，引入新的归一化密度参数解释约束机制，验证了理论预测并揭示了材料影响的相关原因。
摘要：
添加到ITPA全球H模数据库[1]中关于ASDEX-U[2]和JET-ILW的最新数据显示，分界面密度$n_{sep}$与H20因子（相对于ITPA20-IL标度的约束时间）[1]存在相关性。本文对这些趋势展开了详细分析，且证实它们并非接近密度极限的结果。受理论启发，本文引入了归一化分界面密度$n_{sepN} = n_{sep} / \bar{n}$（其中$\bar{n}$为平均密度）。$n_{sepN}$的变化趋势可通过台基特性的两大主要机制——MHD（磁流体动力学）稳定性与最新发展的回旋动理学输运理论——来解释。细致分析表明，这两种机制可在数据中被区分开来。约束时间最显著的提升主要源于台基输运的降低。研究发现，当包含先进H模时，一种纳入了芯部峰化的全新密度峰化定义能最佳解释H20因子：$n_{sepN0} = n_{sep}/n(0)$，即从分界面到磁轴的总密度峰化的倒数。最高H因子的达成，是相对较低的归一化$n_{sepN0}$与较高的沙弗拉诺夫位移或极向β值共同作用的结果。这两个变量的重要性也得到了最新回旋动理学系统分析的理论预测：该系统中存在一种约束，可限制ITG/TEM（离子温度梯度模/捕获电子模）从平衡梯度中获取自由能。数据还显示，面向等离子体部件（PFC）的材料也具有显著影响。这很可能是因为$n(0)/n_{sep}$对实现高H20因子至关重要，同时也与已知的钨（W）会随密度峰化和低输运发生累积的特性有关。初步结果表明，$n_{sepN0}$在存在芯部内输运垒（ITBs）的情况下可能也具有重要作用。
英文摘要：
Recent data, added to the ITPA global H-mode database [1] for ASDEX-U [2] and JET-ILW, reveals that the separatrix density $n_{sep}$ has a correlation with the H20 factor (Confinement time relative to the ITPA20-IL scaling)[1]. These trends are analyzed in detail. They are not a result of proximity to the density limit. The normalized $n_{sepN} = n_{sep} / \bar{n}$ is introduced, motivated by theory ($\bar{n}$ is the average density). The trends in $n_{sepN}$ can be understood in terms of the two main mechanisms of pedestal characteristics -- MHD stability and recently developed theories of gyrokinetic transport. Careful analysis shows these mechanisms can be distinguished in the data. The most dramatic improvement in confinement time arises primarily from reductions in pedestal transport. A new definition of density peaking that includes core peaking is found to best explain H20 when advanced H-modes are included: $n_{sepN0} = n_{sep}/n(0)$, the inverse of the total density peaking from the separatrix to the axis. The highest H-factors are reached by the confluence of relatively low normalized $n_{sepN0}$ plus high Shafranov shift or poloidal beta. The importance of these two variables is also theoretically predicted from recent analysis of the gyrokinetic system, where a constraint can limit the access of ITG/TEM modes to free energy in equilibrium gradients. The Plasma Facing Component (PFC) material also shows a strong influence in the data. This is likely due to the importance of $n(0)/n_{sep}$ to attaining high H20, in conjunction with the known tendency for tungsten (W) to accumulate with density peaking and low transport. Preliminary results indicate that $n_{sepN0}$ might also be important with core ITBs.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
