Analysis of separatrix plasma parameters using local and multi - machine databases 1

The characteristics of the plasma density and temperature at the edge of a diverted tokamak are presented. The analysis is done using the edge database formed by the ITER divertor database and modeling expert group. Analysis indicates the density pro®le is ̄atter with high density operation, i.e. the separatrix density is a larger fraction of the average density. This characteristic is found to be independent of plasma operation mode. We ®nd the separatrix density in ITER will be approximately 6 ́ 10 mÿ3, based on scaling from the major diverted tokamaks. Scaling of the edge temperature is more problematic. A model which concludes the edge temperature is sensitive to details of the recycling process is presented. The temperature pro®le is analyzed to obtain the perpendicular thermal di€usivity. We ®nd a di€usivity of 0.2 m/s for ITER H-mode operation. The existing data, however, does not permit any size scaling of the di€usivity. Ó 1999 Elsevier Science B.V. All rights reserved.