Re: Cathode Films from Sheldahl

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Tue, 25 Mar 2008, Simon Taylor wrote:

Dear all,

I talked with Dan on Friday on this whole business which changing the
cathods. There is the issue for the protoypes and than for the final
chambers.

For the prototypes my understanding is to catch a window of opportunity
before the company doing the etching is going bankrupt, we are considering
to use
a different cathod material with thicker kapton and thinner (0.5 mum) Copper.

To make that very clear that is not really acceptable for me at the
moment. I can explain why. Till now we have not tested the new cathods
with 2 mum Copper in the small scale protoype. Not speaking of the
material with 0.5 mum Copper.

To fabricate full scale cathods costs money and not to little, the money
is only there once. So how do we ensure this material will really work and
we don't end up with a full scale prototype which is not able to give us
answers to the questions we want to know.

So I strongly suggest we take the time now and investigate this very
carefully, like with looking for new vendors (see Fernado's mail) so we
are sure what we build as full scale prototype something which is as close
as possible to what we want to build in the end.
We need also an estimate what this changes do to our budget.

I actually share Simons concerns, are
we sure our handling can not produce cracks in the strips if they are so
thin. Material in the active area is very important and if we can
reduce it very good, but we have to be sure we keep the performance of the
chambers and make handling not a nightmare.

Cheers elke


> Date: Tue, 25 Mar 2008 11:40:57 -0400
> From: Simon Taylor <staylor@jlab.org>
> To: Fernando J. Barbosa <barbosa@jlab.org>
> Cc: Daniel S. Carman <carman@jlab.org>, Roger Flood <flood@jlab.org>,
>      Elke-Caroline Aschenauer <elke@jlab.org>, halld-tracking-hw@jlab.org
> Subject: Re: Cathode Films from Sheldahl
>
> Hi, Fernando,
>
> As far as thickness goes, 900 Angstroms of Gold should be okay:
> For each gold layer I get  900 x 10^-10 m x 19.3 g/cm^3 / (6.4 g/cm^2) =
> 2.7 x 10^-5 X0,
> compared to 1.3 x 10^-4 X0 for 2 microns of Copper.  My concern for such
> a thin layer of conductor is handling:  I can well imagine it could be
> quite easy to cause breaks in the strips due to scratches...  Also, we
> would probably have to do some selective plating near where the strips
> need to be connected to the outside world.
>
> Simon
>
>
> Fernando J. Barbosa wrote:
> >
> > Sheldahl has a series of gold deposited materials that can be used for
> > the cathodes. These materials are normally specified as thermal
> > barriers in satellites but can be used for the FDC cathodes. Part #
> > 146437 (see below) is a standard product with 900 angstroms of Au on
> > 25 micrometer Polyimide and can be delivered in 48 inches wide rolls.
> > The left column below is for standard products (available) and they
> > range from 8 to 127 micrometer Polyimide.
>
>

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