EXPERIMENTAL CONSTRAINTS ON TRANSPORT FROM DIMENSIONLESS PARAMETER SCALING STUDIES

The scalings of heat transport with safety factor (q), normalized coll isionality (nu), plasma beta (beta), and relative gyroradius (rho) ha ve been measured on the DIII-D tokamak [Fusion Technol. 8, 441 (1985)] . The measured rho, beta and nu scalings of heat transport indicate t hat ExB transport from drift wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the s afety factor was varied at fixed magnetic shear, the effective (or one -fluid) thermal diffusivity was found to scale like chi(eff)proportion al to q(2.3+/-0.64), With the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edg e. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, tau(th)proport ional to q(-2.42+/-0.31); however, when the magnetic shear was allowed to vary to keep q(0) fixed during the (edge) safety factor scan, a we aker global dependence was observed, tau(th)proportional to q(95)(-1.4 3+/-0.23). This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined rho, be ta, nu and q scalings of heat transport for H-mode plasmas on DIII-D r eproduce the empirical confinement scaling using physical (dimensional ) parameters with the exception of weaker power degradation. (C) 1998 American Institute of Physics.