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

Tue Aug 4 11:42:08 EDT 2009

From this I calculated that these shields from 3 FDC packages
will make 3.5%RL. At 15 deg it will become 14%.

The contribution seems to be substantial. I suggest to 
remove the shields.

Eugene

------------------------------------------------------
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

On Tue, 4 Aug 2009, Fernando J. Barbosa wrote:

> 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 
>>>> 4ï¿½F 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 ï¿½ .009 inches (ï¿½ .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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