Re: RF Conductivity of thin Mo film

"Uncle Al" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> > >
> > 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.
>

Yes, I discussed this with some of our people who are working the problem
and
they said the cold finger isn't practical for this situlation for your
stated reason  and
for several other reasons.

> 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.

That's a very interesting suggestion, which I will transmit to my coworkers.

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

I am told that they expect the Mo particles to be neutral, so the idea of
using
static electric or magnetic fields had to be abandoned.

Thanks for the constructive thoughts,
Peter