VALIDATION OF A NEW MIXED BOHM GYRO-BOHM MODEL FOR ELECTRON AND ION HEAT-TRANSPORT AGAINST THE ITER, TORE SUPRA AND START DATABASE DISCHARGES/

A new model based on a combination of a Bohm-like term plus a gyro-Boh m-like term is proposed for the electron and ion heat diffusivity in t he L mode regime, which is the commonest regime of operation of tokama ks. This model is derived using the dimensionless analysis technique t aking into account the indications of scaling laws for the global conf inement time and other experimental constraints on the diffusivity. Th e model has been successfully tested against data from several differe nt experiments from the ITER database and the local Tore Supra databas e. Statistical analysis has shown it to perform better than purely Boh m or gyro-Bohm models and global scaling laws in the chosen dataset.