Ablation of tungsten surfaces in collisions with Ar+, He+ and N2+ cation projectiles in the presence of D2

Abstract

Surface ablation of tungsten, known as a plasma-facing material in fusion devices, was investigated mass-spectrometrically in ion beam-type experiments by exposing a tungsten surface in the presence of H2/D2 to fast atomic and molecular projectile ions with high electron-recombination energies (Ar+, He+ and N2+). The sputtered product ions were monitored by high resolution mass spectrometry, in the case of Ar+, at various beam energies, surface temperatures and partial pressures of D2 at beam and product-ion angles of 45°. Bare monatomic and diatomic tungsten ions were seen to be sputtered, more so at elevated ion impact energies and increasing surface temperatures. The relative yield of deuterated WD+ ions was enhanced at higher impact energies and increased partial pressures of D2, but diminished with increasing tungsten temperature. Overall, the observations under our experimental conditions suggest the occurrence of Physical Sputtering (PS) of bare tungsten ions, W+ and W2+, as well as Chemically Assisted Physical Sputtering (CAPS) of WD+ with concomitant dissociation of D2.