Strong drifts effects on neoclassical transport
- Univ. of Trieste (Italy)
- Princeton Univ., NJ (United States); and others
It is well known that strong drifts play an important role in plasma equilibrium, stability and confinement A significant example concerns, in particular for tokamak plasmas, the case of strong toroidal differential rotation produced by E x B drift which is currently regarded as potentially important for its influence in equilibrium, stability and transport. In fact, theoretically, it has been found that shear flow can substantially affect the stability of microinstabilities as well modify substantially transport. Recent experimental observations of enhanced confinement and transport regimes in Tokamaks, show, however, evidence of the existence of strong drifts in the plasma core. These are produced not only by the radial electric field [which gives rise to the E x B drift], but also by density [N{sub s}], temperature [T{sub s}] and mass flow [V = {omega}Re{sub {var_phi}}, with e{sub {var_phi}} the toroidal unit vector, R the distance for the symmetry axis of the torus and {omega} being the toroidal angular rotation velocity] profiles which are suitably steep. This implies that, in a significant part of the plasma core, the relevant scale lengths of the gradients [of N{sub s}, T{sub s}, {omega}], i.e., respectively L{sub N}, L{sub T} and L{sub {omega}} can be as large as the radial scale length characterizing the banana orbits, L{sub b}. Interestingly enough, the transport estimates obtained appear close or even lower than the predictions based on the simplest neoclassical model. However, as is well known, the latter applies, in a strict sense only in the case of weak drifts and also ignoring even the contribution of shear flow related to strong E x B drift. Thus a fundamental problem appears the extension of neoclassical transport theory to include the effect of strong drifts in Tokamak confinement systems. The goal of this investigation is to develop a general formulation of neoclassical transport embodying such important feature.
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 489483
- Report Number(s):
- CONF-960354-; TRN: 97:011630
- Resource Relation:
- Conference: International Sherwood fusion theory conference, Philadelphia, PA (United States), 18-20 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 international Sherwood fusion theory conference; PB: 244 p.
- Country of Publication:
- United States
- Language:
- English
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