Re: FDC cableing

[David Lawrence <davidl@jlab.org>]

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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