Bin W, Buratti P, Cardinali A, Castaldo C, Napoli F, Tudisco O
Institute for Plasma Science and Technology, National Research Council (ISTP-CNR), Milano, Italy.
ENEA, Fusion and Nuclear Safety Department, Frascati, Italy.
Rev Sci Instrum. 2022 Sep 1;93(9):093516. doi: 10.1063/5.0101650.
Electromagnetic waves emitted during a tokamak discharge can be partially ascribed to coupling with plasma waves. In particular, in the presence of runaway electrons, the electromagnetic waves deliver information, otherwise inaccessible, about kinetic instabilities excited by the fast particles. Experiments aimed at studying radio frequency emissions from runaway electron scenarios during different stages of plasma discharge have been carried out at the Frascati Tokamak Upgrade. Frequencies in the range of lower hybrid and whistler waves have been explored, in the presence of relativistic electrons with different energies, ranging from a few to tens of MeV. A pronounced sensitivity of the radio frequency measurements in detecting driven instabilities is observed, providing the possibility to exploit this kind of technique as a monitor of the instability processes and for studies of the fast electron activity. In particular, in this work, we propose a simplified analysis of the frequency scaling of a specific family of kinetic instabilities arising at the lower hybrid frequency range during the current ramp-up stage. The study is performed with respect to the density profile and the wave vector coupling conditions and is aimed at obtaining a rough estimate of the most likely radial location of the interaction between the runaway electron beam and plasma waves at the emission times of the observed signals.
托卡马克放电过程中发射的电磁波可部分归因于与等离子体波的耦合。特别是，在存在逃逸电子的情况下，电磁波能传递有关由快粒子激发的动力学不稳定性的信息，而这些信息用其他方法难以获取。在弗拉斯卡蒂托卡马克升级装置上开展了旨在研究等离子体放电不同阶段逃逸电子情形下射频辐射的实验。在存在能量范围从几兆电子伏特到几十兆电子伏特的相对论电子的情况下，对低杂波和哨声波范围内的频率进行了探索。观察到射频测量在检测受驱动的不稳定性方面具有显著的灵敏度，这使得利用这种技术来监测不稳定性过程以及研究快电子活动成为可能。特别是在这项工作中，我们针对电流上升阶段在低杂波频率范围内出现的特定动力学不稳定性家族的频率标度提出了一种简化分析。该研究是针对密度分布和波矢耦合条件进行的，旨在对观测信号发射时刻逃逸电子束与等离子体波相互作用最可能的径向位置获得一个粗略估计。
