Physical and chemical erosion studies of lithiated ATJ graphite

Lithium evaporation treatments for ATJ graphite tiles in the National Spherical Torus Experiment (NSTX) have shown dramatic improvements in plasma performance increasing the viability of lithium as Plasma Facing Component (PFC) material. In order to understand the complex system of lithiated ATJ graphite, studies of physical and chemical erosion of plain and lithiated ATJ graphite are conducted in the Ion Surface Interaction Experiment (IIAX) facility. Since lithium is known to sputter also as ions, the ionization fraction was measured and found to be 30 ± 6% for a 2000 eV Li ion beam sputtering of lithiated graphite. For chemical erosion measurements, a new facility was developed wherein the target is irradiated with deuterium plasma and the resulting erosion products are detected using a residual gas analyzer. The initial results from this ongoing work are presented here. It is shown qualitatively that lithium treatments suppress the chemical erosion of ATJ graphite.