Causality, intermittence, and crossphase evolution during confinement transitions in the TJ-II stellarator
In this work, we study spontaneous electron to ion root transitions in TJ-II using Langmuir probes. By scanning the probe position on a shot to shot basis, we reconstruct a spatiotemporal map of the evolution of important turbulent quantities in the plasma edge region. We pay particular attention to the evolution of the cross phase between transport-relevant variables, showing the spatiotemporal evolution of this quantity for the first time, revealing the outward propagation of the changes associated with the transition. Additionally, we also compute the intermittence parameter, which allows us to conclude that the turbulence, although its amplitude increases, condenses in a reduced number of dominant modes and becomes less bursty. The causal relationship between variables is studied using the transfer entropy, clarifying the interactions between the main variables and offering a rather complete picture of the complex evolution of the plasma across the confinement transition.
- Research Organization:
- Univ. of Alaska, Fairbanks, AK (United States)
- Sponsoring Organization:
- EUROfusion Consortium; USDOE Office of Science (SC)
- Contributing Organization:
- TJ-II Team
- Grant/Contract Number:
- SC0018076
- OSTI ID:
- 1852486
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 28; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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