An ion cyclotron resonance heating (ICRH) antenna system must launch radio frequency (RF) power with a wavenumber spectrum which maximizes the coupling to the plasma. It should also ensure good absorption while minimizing the wave interaction with the plasma edge. Such interactions lead to impurity release, whose effect has been measured far from the antenna location (Klepper et al. 2013; Wukitch et al. 2017; Perkins et al. 2019) and can involve the entire scrape-off layer. In the normal heating scenario, for which the frequency of the waves launched by the antenna is larger than the ion cyclotron frequency of the majority ions $\omega > \omega _{\textrm {ci},\textrm {maj}}$ , release of impurities due to ICRH can be affected by minimizing the low $|k_{\parallel }| < k_0$ power spectrum components of the antenna. Impurity release can be the result of low central absorption of the waves or power transfer from the fast to the slow wave due to the presence of a confluence in the plasma edge. In ASDEX Upgrade (AUG), a reduction of heavy impurity release by ICRH in the plasma was qualitatively well correlated to the parallel electric field and RF currents flowing around the antenna (Bobkov et al. 2017). In this article, we first show a correlation between the reduction in impurity release by ICRH in AUG and the rejection of the low $|k_{\parallel }| < k_0$ region of the antenna power spectrum. We show that the same correlation holds for results obtained in the Alcator C-Mod tokamak. Finally, using this idea, we reproduce ICRH induced impurity release behaviour in a not yet published experiments of JET, and make predictions for ITER and DEMO.

中文翻译：

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优化相位条件以避免 ICRH 天线的边缘模式激发

离子回旋共振加热 (ICRH) 天线系统必须发射具有波数频谱的射频 (RF) 功率，从而最大限度地耦合到等离子体。它还应确保良好的吸收，同时尽量减少与等离子体边缘的波相互作用。这种相互作用会导致杂质释放，其影响已在远离天线位置的地方进行测量（Klepper等。2013；伍基奇等。2017；帕金斯等。2019），并且可能涉及整个刮除层。在正常加热情况下，天线发射的波的频率大于大多数离子的离子回旋频率 $\omega > \omega _{\textrm {ci},\textrm {maj}}$ ，由于 ICRH 的杂质释放可以通过最小化低 $|k_{\平行}| <k_0$ 天线的功率谱分量。杂质释放可能是由于等离子体边缘存在汇合而导致的波的低中心吸收或从快波到慢波的功率转移的结果。在 ASDEX 升级 (AUG) 中，ICRH 在等离子体中释放的重杂质在质量上与天线周围流动的平行电场和射频电流密切相关（Bobkov等。2017）。在本文中，我们首先展示了 ICRH 在 AUG 中减少杂质释放与拒绝低 $|k_{\平行}| <k_0$ 天线功率谱的区域。我们表明，在 Alcator C-Mod 托卡马克中获得的结果具有相同的相关性。最后，利用这个想法，我们在尚未发表的 JET 实验中重现了 ICRH 诱导的杂质释放行为，并对 ITER 和 DEMO 进行了预测。