The ability to withstand disruptions makes carbon-based materials attractiv
e for use as plasma-facing components in diverters. However, such materials
suffer high erosion rates during attached plasma operation which, in high
power long pulse machines, would give short component lifetimes and high tr
itium inventories. We present the results from recent experiments in DIII-D
, in which the divertor materials evaluation system (DiMES) was used to exa
mine erosion and deposition during short exposures to well-defined plasma c
onditions. These studies show that during operation with detached plasmas,
produced by gas injection, net erosion is suppressed everywhere in the dive
rtor. Net deposition of carbon with deuterium was observed at the inner and
outer strike points and in the private flux region between strike points,
For these low temperature plasmas (T-e < 2 eV), physical sputtering is elim
inated. These results show that with detached plasmas, the location of carb
on net erosion and the carbon impurity source, probably lies outside the di
vertor. Physical or chemical sputtering by charge-exchange neutrals or ions
in the main plasma chamber is a probable source of carbon under these plas
ma conditions, <(c)> 2001 Elsevier Science B,V, All rights reserved.