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Washboard modes as ELM-related events in JET

机译：搓板模式作为JET中与ELM相关的事件

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Washboard (WB) modes (Smeulders P et al 1999 Plasma Phys. Control. Fusion 41 1303) are a very common edge instability regularly observed in the H-mode regime in JET. They are detected as (normally several) bands of continuously fluctuating magnetic activity rotating in the direction of the electron diamagnetic drift with typical frequencies in the range of 10-90 kHz. The time evolution of the WB mode frequency is found to follow qualitatively the evolution of the electron temperature measured near the pedestal top, probably due to the strong diamagnetic drift associated with the large pedestal gradients. Evidence for their involvement in the pedestal and ELM dynamics will be presented. Increasing WB mode amplitude is correlated with an increase in the time between consecutive type-I ELMs. In situations in which a sudden increase (decrease) of WB mode activity is observed, the build-up of the pedestal temperature (and, linked to this, also of the pedestal pressure) of the electrons is seen to become slower (faster). This is a strong indication that the WB mode activity has a regulating effect on the pedestal and that it is responsible for an enhanced transport of energy across the separatrix. The occurrence of a class of type-I ELM precursor modes commonly observed in JET in discharges with low to moderate collisionality (v(e)(*) < 2, roughly) (Perez C P et al EFDA-JET Preprint EFD-P(02)11) is found to be associated with a weakening of the WB modes. The underlying mechanism for this interaction has not been yet identified. In contrast to low triangularity discharges, WB activity is found to increase with gas puffing at high triangularity. This can provide an explanation for the regime recently identified on JET that has been called the mixed type-I/type-II ELM regime (Saibene G et al 2002 Plasma Phys. Control. Fusion 44 1769). A modified version of the peeling-ballooning cycle for type-I ELMs on JET that takes into account the WB mode phenomenon and is consistent with the experimental observations is proposed.
机译：搓板（WB）模式（Smeulders P等人1999 Plasma Phys.Control。Fusion 41 1303）是在JET的H模式下经常观察到的非常常见的边缘不稳定性。它们被检测为（通常为数个）连续波动的磁活动带，它们沿电子反磁漂移的方向旋转，其典型频率在10-90 kHz范围内。发现WB模式频率的时间演变定性地遵循在基座顶部附近测得的电子温度的变化，这可能是由于与大的基座梯度相关的强反磁性漂移。将提供他们参与基座和ELM动力学的证据。 WB模式振幅的增加与连续I型ELM之间的时间增加相关。在观察到WB模式活动突然增加（减少）的情况下，电子的基座温度（以及与此相关的基座压力）的升高会变慢（更快）。这有力地表明了WB模式活动对基座有调节作用，并且它负责增强能量通过头皮的传输。在JET中通常在低至中等碰撞性（v（e）（*）<2，大致如此）的放电中观察到一类I型ELM前体模式的发生（Perez CP等EFDA-JET Preprint EFD-P（02 ）11）被发现与WB模式的减弱有关。尚未确定此交互的基本机制。与低三角形放电相反，发现WB活动随着高三角形充气而增加。这可以为最近在JET上确定的被称为I型/ II型混合ELM混合方案提供解释（Saibene G等人2002 Plasma Phys.Control。Fusion 44 1769）。提出了一种改进的JET上的I型ELM剥离-膨胀循环的版本，该版本考虑了WB模式现象，并且与实验观察结果一致。

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