Dynamic behavior of Li dust in NSTX

A lithium particle dropper was installed on NSTX during the 2008 campaign. Though the primary purpose of the dropper was to study the effects of Li wall conditioning, this experimental configuration also afforded a unique opportunity to study the interaction of dust of a known size and composition with a reactor grade plasma. Li powder was dropped into NSTX at a rate of ∼ 1–35 mg/sec attaining a velocity of ∼ 5 m/s at the plasma boundary. The individual particles rapidly become incandescent due to their interaction with the plasma. Two fast visible cameras, spatially separated by up to 60 degrees, simultaneously viewed the individual particles. Data from the two cameras was used to reconstruct the first detailed 3-D trajectory information of dust in a plasma with a known size, composition and velocity using a 3-D tracking code [1]. These data will be used to further constrain the comparisons to the dust transport codes such as DUSTT used to predict dust behavior in future fusion reactors. Although Li is not presently considered a reactor material, its mass and thus its behavior should be close to that of Be which is a first wall material on ITER.