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Title: Edge electron density profiles and fluctuations measured by two-dimensional beam emission spectroscopy in the KSTAR

Beam emission spectroscopy (BES) system in Korea Superconducting Tokamak Advanced Research (KSTAR) has recently been upgraded. The background intensity was reduced from 30% to 2% by suppressing the stray lights. This allows acquisition of the relative electron density profiles on the plasma edge without background subtraction from the beam power modulation signals. The KSTAR BES system has its spatial resolution of 1 cm, the temporal resolution of 2 MHz, and a total 32 channel (8 radial × 4 poloidal) avalanche photo diode array. Most measurements were done on the plasma edge, r/a ∼ 0.9, with 8 cm radial measurement width that covers the pedestal range. High speed density profile measurements reveal temporal behaviors of fast transient events, such as the precursors of edge localized modes and the transitions between confinement modes. Low background level also allows analysis of the edge density fluctuation patterns with reduced background fluctuations. Propagation of the density structures can be investigated by comparing the phase delays between the spatially distributed channels.
Authors:
;  [1] ; ;  [2] ;  [3]
  1. National Fusion Research Institute, Daejeon (Korea, Republic of)
  2. Wigner RCP Institute for Particle and Nuclear Physics, Budapest (Hungary)
  3. Institute of Nuclear Techniques, Budapest Technical University, Budapest (Hungary)
Publication Date:
OSTI Identifier:
22303719
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAMS; EDGE LOCALIZED MODES; ELECTRON DENSITY; EMISSION SPECTROSCOPY; FLUCTUATIONS; MHZ RANGE; MODULATION; PHOTODIODES; PLASMA; PLASMA CONFINEMENT; PRECURSOR; REPUBLIC OF KOREA; SIGNALS; SPATIAL RESOLUTION; TOKAMAK DEVICES; VISIBLE RADIATION