Surface chemistry and physics of deuterium retention in lithiated graphite

Lithium wall conditioning in TFTR, CDX-U, T-11M, and NSTX is found to yield enhanced plasma performance manifest, in part, through improved deuterium particle control. X-ray photoelectron spectroscopy (XPS) experiments examine the affect of D irradiation on lithiated graphite and show that the surface chemistry of lithiated graphite after D ion bombardment (500 eV/amu) is fundamentally different from that of non-Li conditioned graphite. Instead of simple LiD bonding seen in pure liquid Li, graphite introduces additional complexities. XPS spectra show that Li-O-D (533.0 +/- 0.6 eV) and Li-C-D (291.4 +/- 0.6 eV) bonds, for a nominal Li dose of 2 mu m, become saturated with D at fluences between 3.8 and 5.2 x 10(17) cm(-2). Atomistic modeling indicate that Li-O-D-C interactions may be a result of multibody effects as opposed to molecular bonding. (C) 2010 Elsevier B.V. All rights reserved.