Aachen PK 2003 – wissenschaftliches Programm

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P: Plasmaphysik

P 17: Poster III

P 17.17: Poster

Donnerstag, 20. März 2003, 17:30–19:15, Foyer

Probing Magnetic Turbulence using Runaway Electrons — •H.L.M. Widdershoven and R. Jaspers — FOM-Instituut voor Plasmafysica ’Rijnhuizen’, Association Euratom-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands

Particle and heat transport in tokamaks is anomalously high, reducing the efficiency of a future power plant. A possible cause for the increased transport is turbulence in the magnetic field, but experimentally this turbulence is difficult to probe. In this paper this turbulent transport is evaluated by comparing the measured radiation emitted by runaways with the results from a code which simulates the evolution of runaways in momentum space. Runaways are non-thermal electrons with a very high energy (up to 30 MeV at TEXTOR-94) which are predominantly sensitive to magnetic transport.

Experiments are performed in low density discharges on the TEXTOR-94 tokamak. When an observable runaway electron population is established, the plasma is disturbed by increasing the density or applying various amounts of Neutral Beam Injection (NBI), Ion Cyclotron Resonance Heating (ICRH) or Electron Cyclotron Resonance Heating (ECRH).

It is found that a change in density does not result in increased magnetic turbulence. Results for ECRH are presently inconclusive due to the low power and short duration (275 kW, 0.2 s). Measurements with an upgraded system (1 MW, 10 s) are expected soon. For NBI and ICRH with more power it is found that the magnetically induced transport is enhanced with increasing power.