We generalize the low-gas-puff Heuristic Drift (HD) model of the power scrape-off layer width to take into account both the enhanced parallel confinement time in the SOL at high collisionality, due to enhanced thermal resistivity, and the increase of the upstream temperature at very low collisionality, due to finite target temperature. We find a wide range of separatrix densities over which the original HD model is applicable. However, at the region of high separatrix density and collisionality accessible with strong gas puffs the SOL widens, in reasonable agreement with experimental data from ASDEX-Upgrade and JET. We further find that for typical low-gas-puff H-mode conditions, the projected E$\times$B flow shearing rate in the SOL dominates over the interchange growth rate, while at the high separatrix densities at which H-Modes return to L-Mode, the interchange growth rate approximately equals the shearing rate. The result is related to that of Halpern and Ricci with respect to the steep gradient region of the SOL of inner-wall-limiter discharges, which also show HD-like scale lengths. It is also consistent with calculations of shear-flow stabilization of interchange modes by Zhang and Krasheninnikov. Taking ${\omega }_s>{\gamma }_{\mathit{int}}$ as the criterion for retaining H-Mode performance, we use the generalized HD (GHD) model to predict the scaling for the H$\to$L back transition. The power requirements to sustain H-Mode for existing machines and for ITER are in the range of a factor of 2 below the predictions for the L$\to$H transition, consistent with the limited available studies of H-Mode hysteresis. We find reasonable agreement with the scaling of the density at the H$\to$L back transition found by Bernert on ASDEX-Upgrade. Finally, we speculate that the shearing rate in the SOL of H-Mode plasmas contributes to the reduced core turbulence that supports the formation of the H-Mode pedestal and comment on the implications for ITER.

我们推广了功​​率刮除层宽度的低气吹启发式漂移（HD）模型，以考虑到由于高热阻而导致的高碰撞率下SOL中平行限制时间的增加以及热阻的增加。由于目标温度有限，因此在非常低的碰撞性下的上游温度。我们发现原始HD模型适用的分离密度范围很大。但是，在较高的分离密度和碰撞力较高的区域中，通过强烈的抽吸可以使SOL变宽，这与ASDEX-Upgrade和JET的实验数据合理地吻合。我们进一步发现，对于典型的低气胀H模式条件，预计E$\times$SOL中的B流量剪切速率高于交换速率，而在H-模式返回L-模式的高分离密度下，交换速率大约等于剪切速率。就内壁限制器放电的SOL的陡峭梯度区域而言，该结果与Halpern和Ricci的结果有关，后者也显示出类似HD的尺度长度。这也与Zhang和Krasheninnikov的交换模式的剪切流稳定化计算是一致的。服用${\omega }_s>{\gamma }_{\mathit{整型}}$ 作为保留H模式性能的标准，我们使用广义HD（GHD）模型来预测H模式的缩放比例$\to$L向后过渡。现有机器和ITER维持H模式的功率要求比L的预测低2倍$\to$H过渡，与对H模式磁滞现象的有限研究一致。我们发现与H处的密度缩放比例合理地吻合$\to$Bernert在ASDEX-Upgrade上发现的向后过渡。最后，我们推测H模式等离子体的SOL中的剪切速率有助于降低核心湍流，从而支持H模式基座的形成，并就对ITER的意义进行了评论。