Movie of dust release (demonstration of a plasma-cleaning method)

Here we provide a movie corresponding to data in the paper:

T. M. Flanagan and J. Goree
"Dust release from surfaces exposed to plasma"
submitted to Phys. Plasmas, August 2006.

To view the movie, click one of the links below:

AVI - 30 MB (closer to the original format)
Quicktime - 6 MB (converted from the AVI format)

Comments on this movie

• This movie is a real-time clip from a longer recording made using a side-view video camera operated at 30 fps.
• Our paper reports experimental tests (runs) for many different values of the plasma density n; the movie shown here is for n = 1.9 ´ 10⁸ cm^-3.
• At the beginning of the movie, the spherical sample is illuminated by white light from a hot filament plasma source, and a horizontally-directed cw laser beam passes through the chamber, above the sample.
• A few seconds later, the plasma is turned on, and dust immediately flies off the the surface of the sample, some of it passing through the laser beam above the sample, scattering light which is prominently seen in this movie as tiny streaks in a horizontal band across the image.
• Summary of experimental procedure:
  • A dusty glass sphere is exposed to a 1.0 mTorr neon discharge plasma with an electron beam.
  • The sample rotates on its shaft.
  • Video recording begins, using an NTSC analog video camera fitted with a C-mount lens and no filter.
  • A plasma is suddenly turned on, and its conditions remain constant thereafter. The plasma includes both thermal electrons (n = 1.9 ´ 10⁸ cm^-3) and a 70 eV electron beam (having a much lower density).
  • The electron beam impinges on the top on the rotating sample.
  • When the plasma is turned on, dust is released from the surface of the glass sphere.
  • The dust scatters laser light. This laser-light scattering (LLS) is detected both by a video camera (resulting in the movie provided here) and a photomultiplier tube (yielding a time series of data).

Still images from this movie:

• These pictures are side views. The sample appears as a bright white sphere, and the gray background is the interior wall of our black vacuum vessel. The plasma source, not seen here, is located above the sample.
• The picture on the left is from a frame near the beginning of the movie, when the plasma is first turned on
• The picture on the.right shows the sample much later, after most of the dust has been released from the surface.
• The sample is cleaned everywhere except for a small endcap, which is not directly exposed to the electron beam.
• This result gives evidence that plasma exposure can clean a dusty surface, and it requires the presence of an electron beam.

Beginning: Dust release due to plasma exposure	End: Much of the surface has been cleaned

 

A photograph of our experimental setup: