3D measurements of mobile dust particle trajectories in NSTX

Abstract

The transport of dust particles in plasmas may play a significant role in the performance of next step fusion devices. Highly mobile incandescent dust particles are observed on NSTX for the majority of the discharges using fast visible cameras. Particles are most often born in the divertor region during events such as ELMs or disruptions. Particles born on the midplane are most often deflected by the plasma boundary and remain outside the scrape off layer. The dynamics of the dust trajectories can be quite complex exhibiting a large variation in both speed (10–200m/s) and direction. Particles may have constant velocities or exhibit various degrees of acceleration or deceleration. Abrupt reversals in direction are sometimes observed while some of the larger particles are seen to break apart during mid-flight. 3D trajectories of the dust particles have been derived from measurements of dust trajectories taken simultaneously from two observations points with two fast cameras.