RADIATION-ENHANCED SUBLIMATION OF DOPED GRAPHITES

The radiation-enhanced sublimation (RES) of graphite, doped with boron, silicon and titanium was measured during 1 keV D+ irradiation by line-of-sight quadrupole mass spectroscopy. The RES yield depends on both the dopant element and the dopant concentration as well as on the graphite microstructure. Generally, with a few exceptions for small concentrations, RES decreases with increasing dopant concentration. The most significant reduction in RES is observed for specimens with 13.8% boron and specimens with 5.0% titanium surface concentrations (< 1000 nm). The RES yields at 1800 K for these specimens are reduced by factors of 2 and 4, respectively, compared to the yield for undoped graphite produced by the same fabrication process as the doped specimens, and by factors of 3 and 5, respectively, compared to the yield for pyrolytic graphite.