Re: RF Conductivity of thin Mo film

Uncle Al wrote:
> Peter Simon wrote:
> [snip]
>
>
> > >   Elsewhere I suggested you provide a cold finger to
> > > collect the Mo before it contaminates your radome; why is
> > > that unacceptable?
> >
> > I apologize.  I have never before heard of a "cold finger" and thought
> > that your answer was some kind of jest or sarcastic comment.  Could
> > you please enlighten me on this subject?
>
>
> A cold finger or other cryopanel trap is irrelevant.  If the mean free
> path of the Mo atoms in hard vacuum is larger than the physical
> separation of components, the foulng simply flies in straight lines
> and connects.  A gas curtain won't work for the associated thrust.

  Right. Now that we know the setup, that's obvious.

> The simple (riiight) solution is to have a film periodically pulled
> across betwen the source and the deposition target.  The crud deposits
> on the film and is moved away; the aperture stays clean.  Mylar is
> fragile in a bunch of ways, but poly(ethylene naphthalate) is much
> better and Kapton much better still.  Now you can sweat the MTBF of
> the film and its transport mechanism.

  Sounds like a Real Estate problem now (Location^3). Move 
the damn radome.

> Will a strongly divergent magnetic field sufficiently steer the errant
> atoms?  Pointed or grooved Fe-Nd-B magnets are reasonably cheap.

  Somebody else gets to handle the crud, eh?

  Mark L. Fergerson