Chaotic edge density fluctuations in the Alcator C-Mod tokamak

Analysis of the time series obtained with the O-Mode reflectometer [Rhodes et al., 1997 Plasma Phys. Controlled Fusion 40, 493–510 (1998)] and the gas puff imaging [Cziegler et al., Phys. Plasmas 17(5), 056120 (2010)] systems on the Alcator C-Mod tokamak reveals that the turbulent edge density fluctuations are chaotic. Supporting evidence for this conclusion includes the observation of exponential power spectra (which is associated with Lorentzian-shaped pulses in the time series), the population of the corresponding Bandt-Pompe probability distributions [Bandt and Pompe, Phys. Rev. Lett. 88, 174102 (2002)], and the location of the signal on the complexity-entropy plane (C-H plane) [Rosso et al., Phys. Rev. Lett. 99, 154102 (2007)]. The classification of edge turbulence as chaotic opens the door for further work to understand the underlying process and the impact on turbulent transport.对Alcator C-Mod托卡马克（Alcator C-Mod tokamak）上搭载的O模反射计（O-Mode reflectometer）[Rhodes et al., 1997 Plasma Phys. Controlled Fusion 40, 493–510 (1998)]与喷气成像（gas puff imaging）[Cziegler et al., Phys. Plasmas 17(5), 056120 (2010)]系统所获取的时间序列开展分析，结果表明湍流边缘密度涨落具有混沌特性。支撑该结论的佐证包括：指数型功率谱的观测结果（其与时间序列中的洛伦兹形脉冲相关联）、对应Bandt-Pompe概率分布（Bandt and Pompe, Phys. Rev. Lett. 88, 174102 (2002)）的分布特征，以及信号在复杂度-熵平面（C-H平面）[Rosso et al., Phys. Rev. Lett. 99, 154102 (2007)]上的落点位置。将边缘湍流归类为混沌系统，为进一步探究其内在物理过程以及对湍流输运的影响开辟了研究方向。