Measurements of chemical erosion of ATJ graphite by low energy impact

We report on initial results of chemical sputtering of ATJ graphite by impact of D 2 + in the energy range 30–125 eV/amu. A quadrupole mass spectrometer (QMS) in a UHV scattering chamber was used to monitor the partial pressures of species in the atomic mass range 2–60 amu as a function of the D atom dose accumulated on a graphite sample. Based on in situ measurements of cracking patterns and QMS sensitivities using calibrated leaks, sputtering yields are presented for the production of methane and acetylene for sample temperatures of 300 and 800 K, and energies of 30, 45, and 125 eV/amu. At the lowest investigated impact energy, the contribution of CD4 is found to decrease significantly with increasing temperature, while the contribution of C2D2 is virtually unchanged. For an 800K sample temperature, both the CD4 and C2D2 yields increase with increasing impact energy.