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

Tue Aug 4 11:19:20 EDT 2009

Hi Eugene,

Eugene Chudakov wrote:
> Fernando,
>
> A couple of questions:
> - how many of such cables come from one FDC station (all 6 planes)?
There are 132 cables per FDC package (all 6 planes).
> - what is the diameter of the shield (is it round?)?
The cable is not truly round but oblong in profile with the outer 
diameter ranging from 0.295" to 0.335". The PVC jacket is 0.030" thick 
and the braid shield is about 0.010". Therefore, the diameter of the 
shield ranges from 0.225" to 0.265" (oblong, 0.245" average).

Best regards,
Fernando

>
> 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
>>>
>>> ------------------------------------------------------------------------ 
>>>
>>>
>>> _______________________________________________
>>> Halld-tracking-hw mailing list
>>> Halld-tracking-hw at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw
>>
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