LINE-OF-SIGHT MEASUREMENTS OF THE RADIATION-ENHANCED SUBLIMATION OF GRAPHITE

The radiation-enhanced sublimation of different types of graphite was measured during H+ or D+ irradiation, by line-of-sight quadrupole mass spectroscopy; the quadrupole mass spectrometer was modified to block the transmission of reflected beam particles. The radiation-enhanced sublimation yield depends on both the type and orientation of the graphite; the highest yields (∼0.2 C/D at 1800 K for 1 keV D+) are associated with the most dense and most ordered graphite (pyrolytic graphite, HPG99). The yield at 400 K temperature is of the order of 10-3 C/D for 1 keV D+, more than one order of magnitude lower than the physical sputtering yield. The measured radiation-enhanced sublimation yields are in good agreement with model calculations. © 1995 American Institute of Physics.