Blobs on the High Field Side of Tokamaks

• Turbulence-induced high density filaments, blobs, might represent the new paradigm for radial convectivetransport in the Scrape-Off-Layer of magnetic fusion devices. Models for individual blob dynamics, consideringtheir generation on the Low Field Side (LFS) of the torus have been put forward. We investigate the existence ofblobs in the peripheral region of the High Field Side (HFS) of the FT-2 tokamak. Langmuir probe measurementsare used to detect and characterize blobs. The results were obtained in plasmas with enhanced Lower HybridHeating and data was acquired with a new fast data acquisition system with 50MHz sampling rate. While themajority of the blobs are observed to move towards the wall as expected, some are observed to move inwardstowards the core. This effect is not understood in the light of existing models for the LFS where only the outwarddirection is expected. Further characterization of plasma blobs should therefore involve both HFS and LFS. Thiscould be done at ASDEX Upgrade where reflectometry systems are capable of measuring simultaneously thedensity turbulence on both HFS and LFS. The dependence between radial velocity, size and density of the blobsis also investigated.

Subject headings

NATURVETENSKAP  -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)

Keyword

fusion

plasma turbulence

plasma transport

plasma blob

Langmuir probe

Publication and Content Type

ref (subject category)

art (subject category)