Edge turbulence measurements in toroidal fusion devices

TLDR

Edge turbulence in toroidal fusion devices is characterized by broadband density fluctuations with relative amplitudes of 5–100 %, large potential and electron temperature variations, frequencies around 10 kHz–1 MHz, and filamentary structures spanning 0.1–10 cm across the field and many meters along it, often manifesting as intermittent blobs in the scrape‑off layer. The paper reviews recent measurements of edge plasma turbulence in toroidal magnetic fusion devices, focusing on tokamak results. It surveys diagnostic and data‑analysis methods used to measure edge turbulence and summarizes the main experimental findings. Comparisons with edge turbulence theory are presented, and the authors propose directions for future experiments.

Abstract

This paper reviews measurements of edge plasma turbulence in toroidal magnetic fusion devices with an emphasis on recent results in tokamaks. The dominant feature of edge turbulence is a high level of broadband density fluctuations with a relative amplitude δn/n ∼ 5–100%, accompanied by large potential and electron temperature fluctuations. The frequency range of this turbulence is ∼10 kHz–1 MHz, and the size scale is typically ∼0.1–10 cm perpendicular to the magnetic field but many metres along the magnetic field, i.e. the structure is nearly that of 2D 'filaments'. Large intermittent bursts or 'blobs' are usually observed in the scrape-off layer. Diagnostic and data analysis techniques are reviewed and the main experimental results are summarized. Recent comparisons of experimental results with edge turbulence theory are discussed, and some directions for future experiments are suggested.