The I-mode confinement regime can feature small edge temperature drops that can lead to an increase in the energy deposited onto the divertor targets. In this work, we show that these events are associated with a relaxation of both electron temperature and density edge profiles, with the largest drop found at the pedestal top position. Stability analysis of edge profiles reveals that the operational points are far from the ideal peeling-ballooning boundary. Also, we show that these events appear close to the H-mode transition in the typical I-mode operational space in ASDEX Upgrade, and that no further enhancement of energy confinement is found when they occur. Moreover, scrape-off layer transport during these events is found to be very similar to type-I ELMs, with regard to timescales ($\approx$ 800 $\mu$s), filament propagation, toroidally asymmetric energy effluxes at the midplane and asymmetry between inner and outer divertor deposited energy. In particular, the latter reveals that more energy reaches the outer divertor target. Lastly, first measurements of the divertor peak energy fluence are reported, and projections to ARC - a reactor designed to operate in I-mode - are drawn.

中文翻译：

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ASDEX 升级中的 I 模式基座松弛事件

I 模式限制机制的特点是边缘温度下降很小，这会导致沉积在偏滤器目标上的能量增加。在这项工作中，我们表明这些事件与电子温度和密度边缘分布的弛豫有关，在基座顶部位置发现最大的下降。边缘轮廓的稳定性分析表明，操作点远离理想的剥离-膨胀边界。此外，我们表明，这些事件出现在 ASDEX 升级中典型 I 模式操作空间中的 H 模式转换附近，并且当它们发生时没有发现能量限制的进一步增强。此外，发现在这些事件期间的刮层传输与 I 型 ELM 非常相似，在时间尺度（$\approx$ 800 $\mu$s）、细丝传播、中平面处的环形不对称能量流出以及内部和外部偏滤器沉积能量之间的不对称。特别是，后者表明更多的能量到达外偏滤器目标。最后，报告了偏滤器峰值能量注量的首次测量结果，并绘制了对 ARC（一种设计为在 I 模式下运行的反应堆）的预测。