Erosion, redeposition and boronization lifetime in RFX

In this paper the boronization lifetime in the reversed field pinch experim ent RFX is discussed. It is found that the redeposition of carbon-rich laye rs, which grow during plasma exposure, cover the boron containing layers pr eventing the getter effect through formation of stable boron oxides. Enhanc ed localized erosion on graphite tiles, which constitute the first wall of the experiment, due to magnetic disturbances or held errors is identified a s the source of carbon which codeposits together with hydrogen over the bor onized layers. Samples covered with different boron containing layers have been exposed to the plasma, analyzed by surface techniques and compared. Th e redeposition process is confirmed to be the main cause determining the bo ronization lifetime. (C) 1999 Elsevier Science B.V. All rights reserved.