Beryllium erosion induced by transient heat loads and subsequent reactions in a deuterium plasma

Pulsed laser irradiation (∼0.1–4 MJ/m2 at 1–10 ms) to a beryllium (Be) target has been performed under steady-state deuterium (D) plasma exposure in the linear divertor plasma simulator PISCES-B to investigate the response of Be to transient heat loads such as edge localized modes. Emission intensities from Be atoms and beryllium deuteride (BeD) molecules are observed in front of the Be target by using two fast framing cameras simultaneously; those exhibit similar time evolution to each other, but spatial profiles are different. While the Be I light emission peaks just in front of the target, the BeD emission peaks away from the target. This indicates that Be atoms are directly ejected from the surface, and BeD molecules are volumetrically formed in the plasma. It is also found that the time evolution of light emission can be qualitatively well reproduced by the evaporation flux of Be atoms, estimated from the calculated surface temperature. The Be surface is thought to be eroded as atoms due mainly to evaporation during laser irradiation.

► Pulsed laser irradiation to a beryllium target has been performed under steady-state deuterium (D) plasma exposure.
► Emission intensities from Be atoms and BeD molecules are observed in front of the Be target by using two fast framing cameras.
► Be atoms are directly ejected from the surface, and BeD molecules are volumetrically formed in the plasma.
► The Be surface is thought to be eroded as atoms due mainly to evaporation during laser irradiation.