Turbulence Imaging on the TORPEX Device S H

Turbulence Imaging on the TORPEX Device S. H. Müller, A. Fasoli, B. Labit, O. Pisaturo, M. Podestà, F. M. Poli CRPP – Swiss Federal Institute of Technology Basic confinement mechanism: Toroidal magnetic field with small vertical component: Friction (electron-ion collisions) inhibits parallel motion â electric field persists on equilibrium value F= Particles accelerated along the field lines â circuiting“ of -e. E|| „short electric field vÑB, i B Theory and measurement of confinement time: ÑB vÑB, e ÑB-drifts lead to charge separation and electric fields E Two basic loss channels: cs q Sheath B parallel loss E Ex. B loss 1

Turbulence Imaging on the TORPEX Device S. H. Müller, A. Fasoli, B. Labit, O. Pisaturo, M. Podestà, F. M. Poli CRPP – Swiss Federal Institute of Technology However, simplistic model overestimates confinement time by factor of three -Disagreement seems to be of type of global multiplicative factor ® Missing transport channel? ® must show same Bz dependence -Turbulence? ® Possible, as Bz plays also key role for turbulence (connection length prop. to Bz-1) -Look at fluctuations as function of Bz (hydrogen plasma): A lot of reproducible, non-trivial variation ® ideal prerequisites for further investigations, in particular: comparison with numerical simulations 2

Turbulence Imaging on the TORPEX Device S. H. Müller, A. Fasoli, B. Labit, O. Pisaturo, M. Podestà, F. M. Poli CRPP – Swiss Federal Institute of Technology Diagnostic development for turbulence imaging: HEXTIP • • • Goal Space and time Background and fluctuations Ion saturation current and/or floating potential Design 4 independent rings mountable at different toroidal positions 86 ring-shaped tips separated by 3. 5 cm Mounted on TORPEX mobile sector Tests and preliminary results: 3