Re: capillary effect

[Ludwik Kowalski <kowalskil@MAIL.MONTCLAIR.EDU>]

1) I had to look into my thesis, defended in June 1993, to
answer Bernard's second question. The first answer is
simple, you pool a rigid frame supporting the foil (slightly
tilted) and hope for the best. Watching mercury and
knowing when and how to tilt was essential. As I said,
the success rate was about 50%, after a lot of practice.

2) To answer the second question let me paraphrase
what I read in my thesis; it is in French. You make a
solution of cellulose in the "acetate d'isoamyle"
(about 0.2 grams per 100 cc) and poor it on the
tilted glass plate. The plate dries in the vertical
position and a thin layer of cellulose if formed on
glass. The next step is to place this thin layer on the
surface of water, a very delicate and slow operation.
The edges are scratched with a blade and the plate
is lowered into water at 45 degrees, very slowly.

The third step was to place the rigid frame into the
water, below the floating layer, and pool it out, very
slowly with the layer on top of it. This was also a
delicate step; the size of the opening in the Al frame
was 12 cm  by 11 cm. Then came the capillary
deposition step which was already described. The
net result was up to 0.6 mg/cm^2 of uranium on the
0.02 mg/cm^2 of cellulose. I hope this information
will be useful to somebody; please let me know.

P.S. What was the frame so large? Because the
protons beam used in our experiment was often
used by other people at the same time. Their setup
was further downstream and they wanted to be sure
that nothing thick was on the way. With a big frame,
which could be lowered if necessary, I was able to
get as much machine time I wanted (instead of
begging for an hour or two of beam time each week.
Ludwik Kowalski

On Monday, Jun 2, 2003, at 03:52 US/Eastern, Bernard Cleyet wrote:

> How did you separate the film from the Hg, and what was the composition
> of the film?
>
> My thesis advisor (late '50's) used zapon on water, lifted the zapon
> with wire loops, then used the film as a substrate to evaporate
> selenium.  The final step was to dissolve the zapon after mounting the
> film along with many more on a frame.  Result:  a pile of plates
> polarizer for the IR.
>
> bc
>
> p.s. because  their specific activity is much greater?
>
> Ludwik Kowalski wrote:
>
> > On Sunday, Jun 1, 2003, Bernard Cleyet asked:
> >
> > > Was any care taken to ensure none of the uranium
> > > went up your noses?
> >
> > Yes, hoods were available but not always used. I would
> > be much more careful in working with Pu, Am or Cf.
> >
> > > Did you use Al foil or something thinner like zapon?
> >
> > To deposit uranium on a very thin dielectric film I used
> > mercury below it. The mercury was on a paraffin plate,
> > for example, in a 5 mm by 15 mm cavity carved to match
> > the desired target shape. The potential difference was
> > applied between the wire in the capillary tube and the
> > wire in mercury. The film, initially ~1mm from mercury,
> > would be attracted to it after the voltage was applied.
> > The rate of success in separating thin films from mercury,
> > after depositing uranium,  was something like 50%.
> > Using mercury in this way was my own "invention."