This paper presents initial results from experimental observation of edge turbulence structures in ohmically heated plasmas on Tokyo Spherical Tokamak-2 (TST-2). The experiment was conducted using two-dimensionally movable Langmuir probes. With monitoring floating potential V f and ion saturation current I is, the radial and poloidal structures of the edge turbulence are obtained. The high coherence in fluctuations at 10-100kHz frequency was observed by the use of the Langmuir probes 90° toroidally and ∼75° poloidally distant from each other, suggesting that the fluctuations have long range correlation along a magnetic field line. To investigate nonlinear structures of the turbulence, bispectral analysis was used, and the observed auto-bicoherence pattern suggests the presence of the coupling and energy transfer between different modes.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering