[Halld-tracking-hw] CDC endplates, feedthrus etc (fwd)

[Eugene Chudakov]

Fernando,

A couple of questions:
- how many of such cables come from one FDC station (all 6 planes)?
- what is the diameter of the shield (is it round?)?

Thanks,
Eugene


------------------------------------------------------
Eugene Chudakov
http://www.jlab.org/~gen
phone (757) 269 6959, 5352  fax (757) 269 5703
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave, Suite #4
Newport News, VA 23606 USA

On Sat, 1 Aug 2009, Fernando J. Barbosa wrote:

> Hi Eugene,
>
> While we are on the subject, we need to decide if we want to remove the 
> shield braid from the FDC signal cables.
>
> It has been our intention to remove the shield braid (~0.010" Cu thickness) 
> from the FDC signal cables inside the magnet. The cable inside the magnet is 
> still shielded by an Al foil (which is part of the cable, the cable has the 
> Cu braid over the Al foil) and will then be protected by a PVC sleeve. The 
> cost of the cable assemblies will be lower if we don't need to remove the 
> braid.
>
> I suggest running some simulations soon as we are about to make some cables 
> for the FDC prototype and this would be a good time to finalize the cable 
> specs.
>
> Best regards,
> Fernando
>
>
>
> Eugene Chudakov wrote:
>> Tim suggests to use 6mm aluminum instead of 6mm carbon fiber
>> composite material for the downstream endplate of the CDC.
>> We made an estimate of the thicknesses involved:
>> 
>> a) The inserts (donuts, feedthroughs, pins etc.): 3.6% RL
>> b) The composite endplate (the holes make about 30% of the surface): 1.9%
>> b) The Al endplate with holes: 4.7%
>> 
>> Changing the plate to Al will add 2.8% of RL,
>> which is an additional loss of 11% of events with 4-photons passing the 
>> plate,
>> and a 20% increase of the scattering angle of charged particles in the 
>> plate.
>> It does not sound dramatic, unless there are many similar compromises
>> in storage.
>> 
>> ------------------------------------------------------
>> Eugene Chudakov
>> http://www.jlab.org/~gen
>> phone (757) 269 5352 fax (757) 269 5703
>> Thomas Jefferson National Accelerator Facility
>> 12000 Jefferson Ave, Suite #4
>> Newport News, VA 23606 USA
>> 
>> ---------- Forwarded message ----------
>> Date: Fri, 31 Jul 2009 11:24:12 -0400
>> From: Tim Whitlatch <whitey at jlab.org>
>> To: Curtis A. Meyer <cmeyer at ernest.phys.cmu.edu>
>> Cc: Beni Zihlmann <zihlmann at jlab.org>, Eugene Chudakov <gen at jlab.org>,
>> Vladislav Razmyslovich <vgr at jlab.org>, Gary Wilkin <wilkin at andrew.cmu.edu>
>> Subject: CDC endplates, feedthrus etc
>> 
>> Hi Curtis,
>> 
>> After working with several vendors on the manufacturing of these parts, I 
>> offer the following information and suggestions;
>> 
>> 1. Endplate stereo angles position tolerances should be opened up. The 
>> stereo holes .positional tolerance between 005 and .010 in. may be 
>> possible. A change in temperature between machining and measuring of 4�F 
>> will cause a change of .0025 in. on the outermost holes.
>> 
>> Recommendation: Stereo hole positions be opened up to .007, straight holes 
>> to .005. The positions of the crimp pins can be determined as installed by 
>> photogrammetry or CMM. (within .002)
>> 
>> 2. Downstream endplate of carbon/epoxy composite will need to be custom 
>> made. The thickness tolerance will be � .009 inches (� .005 for alum. 
>> plate). The plate is .236 inches thick. If we make it thicker and machine 
>> it, there is a chance for warpage. The cost is about $15K additional for 
>> the composite and the results are questionable.
>> 
>> Recommendation: Make downstream plate out of .25 in.aluminum. The density 
>> of the carbon epoxy is about 60% of aluminum. The 3600 holes in the 
>> endplate remove about 1/2 of the material. The feedthrus donuts and inserts 
>> dominate the mass in the area..
>> 
>> 3. The plastic feedthrus can be injection molded for about half the price 
>> of the machined parts ($113K in savings). They can be injection molded if 
>> the diametral tolerances are opened to .002 to .003 inches. The aluminum 
>> parts would also be cheaper with looser tolerances (.001 in).
>> 
>> Recommendation: Open up tolerance on components as stated above.
>> 
>> Slava has updated the drawings showing many of these options. please see 
>> them at:
>> 
>> http://www.jlab.org/~vgr/CDC%20Updated%20Drawings-7-30-2009/
>> 
>> Please consider these changes and let me know what you think.
>> 
>> Thanks,
>> 
>> Tim
>> 
>> ------------------------------------------------------------------------
>> 
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