Movie of dust release (demonstration of a plasma-cleaning
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
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:
this page created June 23, 2006, updated August 23, 2006