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[Gerard Visser <gvisser AT indiana.edu>]

hi Mike,
	I think it would be electrically OK to do have a little extra portion without 
jacket and shield, IF necessary. At the moment I'd have to say it is not clear 
to me why the cable should run in that direction, but I have not, as far as I 
recall, seen a sketch of the cable routing plan near the disks. I assume it will 
be something similar to what we did for the FGT -- cable runs straight out of 
the T board (as seen in your picture before the 90 deg bend, i.e., no 90 deg 
bend there), follows for a little bit along the periphery of that disk's support 
ring, is strain relievd to that ring there somewhere/somehow (this is at a point 
10-20 cm from the T-board) and then makes a simple gentle 90 degree bend to 
follow a path out of the cone structure outboard of the other disks. Seems to me 
this should work here as well. I guess we either have to look at a complete 
sketch/drawing of the assembly with cooling lines and cables, or look at the 
real assembly when we have that. I would certainly not run the cable out without 
having some strain relief to the same disk structure somehow.
	It would be best if all test support structures for the FST wedge are 
compatible with same T-board/cable plan as will be used in the final assembly. 
It seems to me this should be feasible.
        Sincerely,

                Gerard


p.s. Mike, by the way, when you have some purple cable please send me a few feet 
of it for evaluation. (Someone should measure characteristic impedance of the 
pair -- you can best do that but if you want me to that's fine, then give me a 
10 foot sample please. Otherwise 2 foot is fine.)


On 12/23/2019 9:04 AM, Capotosto, Michael wrote:
> Zhenyu,
>
> Sorry for the late reply. I don't think the T-Board/cable should be much of an issue - 
> We were able to squeeze the cable down where it soldered to the boards to quite a small 
> height with the V2.1 test stand boards. The bulk of the cables where they solder to the 
> board will be considerably less for the V3.0 T-Boards, as we omitted the heat shrink 
> labels. The cable itself is also going to be a smaller diameter - It will be a single 
> molded "Purple" cable - compared to the bundle of 3 cables used for the V2.1 
> test stand cables.
>
> I've attached a picture of the V2.1 test stand cable and board assembly that Steve 
> distributed some time ago for reference. The height being measured will probably be 
> about the same, however the bundle covered by the white sleeve will be significantly 
> smaller - from 0.645" (~16.4mm) (pictured) to ~0.415" (~10.5mm).
>
> We were able to put a tight bend in the wires by removing a little bit of extra 
> jacket and shield from the cables as seen in the picture, we can do the same if 
> need be for the production units. I don't think an extra 1" (25.4mm) of 
> shield will have much affect on signal integrity, but if we do find it necessary 
> I'd like to hear Gerard's thoughts.
>
> --Mike
>
>
>
> -----Original Message-----
> From: Ye, Zhenyu <yezhenyu AT uic.edu>
> Sent: Friday, December 20, 2019 12:39 PM
> To: Han-Sheng Li <acidhf AT gmail.com>; Capotosto, Michael <capotosto AT bnl.gov>
> Cc: star-fst-l AT lists.bnl.gov
> Subject: Question on T-board/Inner Signal Cable
>
> Hi Mike,
>
> Xu and I are trying to come to a conceptual design for a structure holding a 
> FST module in the cosmic and laser test stands (see 
> https://drupal.star.bnl.gov/STAR/system/files/FSTTestStand_UIC.pdf )
>
> We are thinking of using the holding box that Han-Sheng and Yi are designing 
> (shown on slide 6 
> https://drupal.star.bnl.gov/STAR/system/files/YiYang_FST_MS_20191219.pdf )
>
> But we are not sure if the T-board/Inner Signal Cable would be in the way 
> when we try to connect it to the module in the box. Can you please tell me 
> what your assessment is?
>
> P.S. Han-Sheng, can you please post the design files for the holding box?
>
> Thanks
> Zhenyu
>
>
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