3-D reconstruction of incandescent lithium dust particle trajectories in NSTX

Dust control is a key safety and stability concern for ``next-step'' fusion devices, so understanding the dynamics of dust in a fusion grade reactor is an important issue. Here, a large ensemble of trajectories from pre-characterized lithium dust is collected with the goal of verifying the various dust transport codes. Precise amounts of 40 $\mu $ lithium dust (varying from 1-150 mg) are injected into the National Spherical Torus Experiment (NSTX) plasma using a powder dropper based on a vibrating piezo crystal. The particles are heated to incandescence by electron bombardment, allowing them to be viewed by two separated visible-range fast cameras operating at $\sim $ 10,000 frames per second. The tracks from both cameras can be combined to form a single, 3-D trajectory. Particles are observed to undergo a variety of accelerations both parallel and perpendicular to the magnetic field, depending on their proximity to the scrape-off layer. The velocity, lifetime, and ionization state of the particles will be discussed.