COMPARISON OF WALL DIVERTOR DEUTERIUM RETENTION AND PLASMA FUELING REQUIREMENTS ON THE DIII-D, TDEV AND ASDEX UPGRADE TOKAMAKS/

We present a comparison of the wall deuterium retention and plasma fue ling requirements of three diverted tokamaks, DIII-D, TdeV and ASDEX U pgrade, with different fractions of graphite coverage of stainless ste el or Inconel outer walls and different healing modes. Data from parti cle balance experiments on each tokamak demonstrate well-defined diffe rences in wall retention of deuterium gas, even though all three tokam aks have complete graphite coverage of divertor components and all thr ee are routinely boronized. This paper compares the evolution of the c hange in wall loading and net fueling efficiency for gas during dedica ted experiments without helium glow discharge cleaning on the DIII-D a nd TdeV tokamaks. On the DIII-D tokamak, it was demonstrated that the wall loading could be increased by > 1250 Torr 1 (equivalent to 150 x plasma particle content) plasma inventories resulting in an increase i n fueling efficiency from 0.08 to 0.25, whereas the wall loading on th e TdeV tokamak could only be increased by < 35 Torr 1 (equivalent to 5 0 x plasma particle content) plasma inventories at a maximum fueling e fficiency similar to 1. Data from the ASDEX Upgrade tokamak suggests q ualitative behavior of wall retention and fueling efficiency similar t o DIII-D.