skip to main content

SciTech ConnectSciTech Connect

Title: The appearance and propagation of filaments in the private flux region in Mega Amp Spherical Tokamak

The transport of particles via intermittent filamentary structures in the private flux region (PFR) of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-facing surfaces in the divertor. The visible camera data suggest that, in the divertor volume, fluctuations in light emission above the X-point are strongest in the scrape-off layer (SOL). Conversely, in the region below the X-point, it is found that these fluctuations are strongest in the PFR of the inner divertor leg. Detailed analysis of the appearance of these filaments in the camera data suggests that they are approximately circular, around 1–2 cm in diameter, but appear more elongated near the divertor target. The most probable toroidal quasi-mode number is between 2 and 3. These filaments eject plasma deeper into the private flux region, sometimes by the production of secondary filaments, moving at a speed of 0.5–1.0 km/s. Probe measurements at the inner divertor target suggest that the fluctuations in the particle flux to the inner target are strongest in the private flux region, and that the amplitude andmore » distribution of these fluctuations are insensitive to the electron density of the core plasma, auxiliary heating and whether the plasma is single-null or double-null. It is found that the e-folding width of the time-average particle flux in the PFR decreases with increasing plasma current, but the fluctuations appear to be unaffected. At the outer divertor target, the fluctuations in particle and power fluxes are strongest in the SOL.« less
Authors:
; ;  [1] ;  [2]
  1. CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
  2. York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)
Publication Date:
OSTI Identifier:
22490165
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 9; Other Information: (c) 2015 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; AUXILIARY HEATING; CAMERAS; DIVERTORS; ELECTRIC CURRENTS; ELECTRON DENSITY; FIRST WALL; FLUCTUATIONS; LANGMUIR PROBE; MAST TOKAMAK; PLASMA; PLASMA SCRAPE-OFF LAYER; SPHERICAL CONFIGURATION; THERMOGRAPHY; TRANSPORT THEORY; VISIBLE RADIATION