TRANSPORT IN NON-AXISYMMETRICAL TORI WITH UP DOWN ASYMMETRY

Transport phenomena arising from the up-down asymmetry of ripple and h elical perturbations of the magnetic field in tokamaks and stellarator s are investigated. Accounting for this asymmetry is important for dev ices with vertically displaced magnetic axes or with a single null div ertor. The asymmetry manifests itself in different magnitudes of the r ipple or helical perturbations in the up and down parts of the magneti c surface. Owing to this difference, the toroidally trapped particles acquire a net radial drift. The collisionless dynamics of the particle s in such configurations are studied, as well as the solutions of the kinetic equation. It is shown that, in spite of the net radial drift, the up-down asymmetry does not lead to enhanced diffusive transport, c ompared with the conventional ripple transport, although the convectiv e loss at low collisionality might be large.