A type 2 cathode spot moving across the surface of a powder covered electrode, ejecting powder into an overhead plasma is captured with a high frame rate camera. The stream of ejected powder becomes visible as the cathode spot (the bright dot moving from right to left) enters the laser interrogation region (the stationary, bright circular region on the electrode surface). The sequence is captured at 2000 frames per second (fps) with a maximum exposure time of 497 microseconds. The cathode spot is moving in the retrograde or -JxB direction in the presence of a static magnetic field.
A cathode spot and subsequent stream of powder emanating from the electrode is more clearly visible in this video sequence. The high frame rate camera was operated at 1000 fps with a 997 microsecond exposure time. These particles follow a ballistic trajectory after ejection and particle tracking allows the distribution of initial particle ejection velocities to be calculated.
These two video sequences were captured in connection with research investigating the affects of solid particle dispersion into an overhead plasma for hypersonic communications applications.