Re: FDC cableing

[Elton Smith <elton@jlab.org>]

Hi Dave and Joe,

There is also the issue of grounding at different frequencies. The copper
is great at low frequencies and can handle quite a bit of current. The Al
is thin but covers 100% and can shield higher frequency components.

Cheers, Elton.


Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625

On Thu, 7 Jun 2007, David Lawrence wrote:

>
> Hi Joe,
>
>     I'm not an expert, but when I ordered coaxial cable for PrimEx, I
> was advised to get the mylar layer not as a grounding shield, but to
> block contamination of chemicals leaking from the outer jacket into the
> diaelectric and changing the propagation properties over time. I was
> also told that this was even desirable for "non-contaminating" jackets
> since they were really just "less" contaminating. Bill Stephens was the
> person who advised me. I think he may be retired now, but he was an
> electrical engineer at UVa who had a lot of experience with these
> things. I'm not even sure what type of cable this is you're looking at,
> but thought I'd throw this in FYI.
>
> Regards,
> -David
>
> Joe Beaufait wrote:
> > I am glad we have decided to go ahead and purchase a sample of the 25
> > pr. cable. This cable is going to be the standard for much of the data
> > acquisition system and it would be very nice to see how hard it is to
> > work with.
> >
> > On that note, there were some comments made at the Wednesday FDC
> > meeting  concerning the possible redesign of the cable. Daniel
> > mentioned that we might ask to make the outer jacket thiner and I
> > promised to look into it but, while looking at the cable diagram I
> > also noticed that this cable is double shielded. It has an aluminized
> > mylar layer with drain wire, and a copper braid. I believe we could do
> > away with the copper braid and reduce the copper in the cable by at
> > least half.
> >
> > I would like comments from the group on whether or not you would like
> > me  to pursue this.
> >
> > Thanks
> > Joe
> >
>
> --
>
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>   David Lawrence Ph.D.
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