PREDICTIVE TRANSPORT SIMULATIONS OF JET L-MODE AND H-MODE GYRO-RADIUSSCALING EXPERIMENTS

Predictive transport code simulations of gyro-radius scaling experimen ts have been performed using experimental data from JET profile databa ses. Both L mode and H mode discharges are considered. Self-consistent ly derived steady state profiles of electron and impurity density, tem peratures and heat diffusivities are compared with the experimental pr ofiles. The simulations are based on a first principle gyro-Bohm trans port model for ion temperature gradient (ITG) modes, impurity modes an d collisionless trapped electron (CTE) modes. In the good confinement region, the experimental profiles as well as the transport scalings ar e well reproduced by the simulations. In particular, apparent Bohm-and Goldston-like scalings of the local diffusivities are obtained in the L mode simulations, whereas gyro-Bohm scalings are obtained in the H mode scans. The scalings obtained in the L mode simulations are a resu lt of small systematic deviations in the similarity conditions between the low field and high field discharges. In the H mode simulations, t he profile effects are generally smaller, resulting in a gyro-Bohm sca ling of the heat diffusivities. Since profile effects arise through th e edge boundary conditions, the different scalings obtained in the sim ulations are attributed to differences in edge confinement between L a nd H mode plasmas.