Utilization of boron particulate wall conditioning in the full tungsten environment of WEST

Abstract

Over a series of experiments performed on the WEST device we have demonstrated the ability to perform controlled impurity injections and improve overall wall conditions. Positive changes to overall machine conditions are evidenced by reduced native impurity content after injection as well as decreases in radiated power and reductions in recycling. These results are consistent with the formation of a gettering layer which provides a particle sink and a reduction of source terms. We also observe a reduction in overall Zeff at the conclusion of the powder injection period consistent with a reduced impurity burden within the plasma. Finally, we have demonstrated a minimal injection quantity required to affect a positive change in wall conditions. These results confirm that plasma assisted deposition of conditioning material through particulate injection shows substantial promise as a supplemental wall conditioning technique.