Measurement of high-temperature microparticle acceleration through imaging

Abstract: Microparticles ranging from sub-microns to millimeter in size are a common form of matter in magnetic fusion environment, and they are highly mobile due to their small mass. Different forces in addition to gravity can affect their motion both inside and outside the plasmas. Several recent advances open up new diagnostic possibilities to characterize the particle motion and their forces: high-speed imaging camera technology, microparticle injection techniques developed for fusion, and image processing software. Extending our earlier work on high-temperature 4D microparticle tracking using exploding wires, we report latest results on time-resolved microparticle acceleration measurement. New particle tracking algorithm is found to be effective in particle tracking even when there are a large number of particles close to each other. Epipolar constraint is used for track-pairing from two-camera views. Error field based on epi-geometry model is characterized based on a large set of 2D track data and 3D track reconstructions. Accelerations based on individual reconstructed 3D tracks are obtained. Force sensitivity on the order of ten gravitational acceleration has achieved. High-speed imaging is a useful diagnostic tool for microparticle physics, computer model validation and mass injection technology development for magnetic fusion.