论文标题
通过使用两流体模拟，调查了Tokamak边缘中的湍流运输方式
Investigation of turbulent transport regimes in the tokamak edge by using two-fluid simulations
论文作者
论文摘要
单个NULL配置中通量驱动的两流体模拟的结果用于研究确定Tokamak边缘中湍流传输的过程。 Three turbulent transport regimes are identified: (i) a developed transport regime with turbulence driven by an interchange instability, which shares a number of features with the standard L-mode of tokamak operation, (ii) a suppressed transport regime, characterized by a higher value of the energy confinement time, low-amplitude relative fluctuations driven by a Kelvin-Helmholtz instability, a strong E x B sheared flow, and the formation of召回H模式的传输屏障和（iii）降级的禁闭状态，其特征是灾难性较大的互换驱动的湍流转运，这提醒了格林瓦尔德密度限制的交叉。我们得出了这三个制度中压力梯度长度的分析表达。通过增加热源或减少碰撞性，从发达的运输性转移到从发达的运输方式到降级的禁闭状态的过渡来获得从发达的运输方式到抑制运输方式的过渡。功率阈值的分析表达，以访问与H模式访问的功率阈值相关的被抑制运输方式，以及在输入与Greenwald密度相关的退化限制机制之前可实现的最大密度。检索了H模式访问的功率阈值的实验依赖性，Tokamak大半径和同位素质量的实验阈值。密度极限的分析估计值包含对等离子体电流和Tokamak小半径的正确依赖性。
The results of flux-driven, two-fluid simulations in single-null configurations are used to investigate the processes determining the turbulent transport in the tokamak edge. Three turbulent transport regimes are identified: (i) a developed transport regime with turbulence driven by an interchange instability, which shares a number of features with the standard L-mode of tokamak operation, (ii) a suppressed transport regime, characterized by a higher value of the energy confinement time, low-amplitude relative fluctuations driven by a Kelvin-Helmholtz instability, a strong E x B sheared flow, and the formation of a transport barrier, which recalls the H-mode, and (iii) a degraded confinement regime, characterized by a catastrophically large interchange-driven turbulent transport, which reminds the crossing of the Greenwald density limit.We derive an analytical expression of the pressure gradient length in the three regimes. The transition from the developed to the suppressed transport regime is obtained by increasing the heat source or decreasing the collisionality and vice versa for the transition from the developed transport regime to the degraded confinement regime. An analytical expression of the power threshold to access the suppressed transport regime, linked to the power threshold for H-mode access, as well as the maximum density achievable before entering the degraded confinement regime, related to the Greenwald density, are also derived. The experimental dependencies of the power threshold for H-mode access on density, tokamak major radius, and isotope mass are retrieved. The analytical estimate of the density limit contains the correct dependence on the plasma current and on the tokamak minor radius.
