Hannover 2010 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 20: Poster: Magnetic Confinement

P 20.3: Poster

Donnerstag, 11. März 2010, 16:00–18:00, Lichthof

Non-resonant heating in TJ-K — •Alf Köhn, Peter Diez, Sebastian Enge, Eberhard Holzhauer, Stefan Merli, Mirko Ramisch, and Ulrich Stroth — Institut für Plasmaforschung, Universität Stuttgart

At magnetic field strengths of B₀≈270 mT, non-resonant heating with f₁=2.45 GHz is observed in TJ-K. To this end, a plasma needs to be started with a heating system, operating at f₂=8.3 GHz, whose corresponding electron cyclotron resonance ω_ce is located inside the confinement region. Additional heating of the plasma is then observed if f₁ is switched on. High densities of n_e≈10¹⁸ m⁻³ are achieved, which stay at this high level, even if f₂ is switched off. Due to the absence of the cyclotron resonance, ω₁<ω_ce, and the absence of the upper hybrid resonance, ω₁<ω_UH, this regime is referred to as non-resonant heating regime. At the high magnetic field, it is not possible to start a discharge with f₁ only. A minimum density is necessary to start the non-resonant heating. This minimum density was determined to be in the range of the cutoff density. Power modulation studies at frequencies above the inverse confinement time, indicate the left-hand cutoff, ω_L, as the location of power deposition. Toroidal net currents which are up to 50 times higher than in low-field discharges are detected by a Rogowski coil. An overview of the plasma parameters achieved in this regime and a discussion of possible heating mechanisms will be presented.