The role of beryllium deuteride in plasma-beryllium interactions

Beryllium deuteride has been measured in plasma-exposed surfaces and in the plasma column of the PISCES-B experiment. XPS measurements of high-purity BeH2 samples, used as standards, confirm the presence of beryllium deuteride in beryllium codeposited material (Be 1s energy of BeH2 bond = 115.0 eV). TDS measurements of high-purity BeD2 samples are used to accurately determine the decomposition temperature of the beryllium deuteride molecule (∼540 K). Deuterium release is observed from plasma-exposed beryllium samples and from Be codeposited layers at this temperature. BeD molecular (A-X) band emission is observed in beryllium seeded plasma discharges and during deuterium sputtering measurements of beryllium. Band emission intensities during Be-seeding are used to estimate the photon emission coefficient, <σv>, for the band. The <σv> value verifies that molecular sputtering of BeD (from beryllium targets saturated with deuterium from the plasma exposure) is a small fraction of the physical sputtering of beryllium atoms.