Re: CDC Interconnect Concepts - EDAC

[Yves Van Haarlem <yvhaarle@ernest.phys.cmu.edu>]

Hi All,

About the phone conference. Curtis is at JLab next week and he can meet 
all Wednesday, Gerard and me could phone in. So what about having a 
meeting next week Wednesday at 1pm (first iteration)?

Here are some comments on comments:

>>> In particular, I find the cable length from the straws to the preamp card 
>>> of
>>> about 8" to be excessive and with limited shielding, from outside and 
>>> between
>>> channels. 
>
> Me too. This is an issue not of ease of construction, but of performance (EMI 
> sensitivity). Yves, maybe it is in fact impossible to do better, but it 
> should at least be recognized as risky and cannot be lightly dismissed just 
> because "it only has to be connected once." This is _not_ Fernando's main 
> point, I believe.

The 8" length is an absolute maximum - we are reviewing an option from 
Slava/Tim that would reduce that length significantly (we could go into 
this in the phone conference).


> But, on the other hand, what part number are you looking at specifically,
341-026-500-202 
> Yves. I just now checked EDAC website, for instance this connector looks 
> fairly suitable: 
> http://www.edac.net/downloads/306-316-356%20Series%20Spec%20Sheet.pdf
> It has a rating of 2545 VDC between adjacent contacts! It comes with card 
> guides as an option. Looks good to me.

Gerard, when you were here you recommended the 341 series. Also, before I 
ordered them I've sent a mail to the tracking list. Anyway: I took a 
connector with a double row connectors because that was the only one I 
could order (i preferred the single row at that time to have a stronger 
connection with the HV board). There was only one company that could 
deliver them (www.newark.com, delivery time was 2 months) and they could 
only deliver the 341-026-500-202. I even called EDAC and the result was 
that our possible order was not enough (I told them that we might order 
200 of those connectors) to start a production line (they do not have them 
in stock). I just did a little surfing for the 306/316/356 series and see 
a similar problem: no single row connectors with enough contacts available 
to be ordered immediately (but it might be my surfing).

We can look into the 306 series but for the test with the new prototype 
we'll most likely use the 341-026-500-202 (depending on when it will be 
build): this has implications for the HV board design to be used with the 
new prototype.

>>> Presently, according to Yves' drawings, the 26 contact connector
>>> connects 24 straws and 2 contacts are used for grounding the preamp 
>>> carrier
>>> PCB to some ground point, presumably the end plate.
>> Maybe I did it wrong in the drawing but we do not plan to use the two
>> remaining contacts for grounding for the reason you mention.
>
> No, Yves, I think you do... Or at least, I think you should. The preamp 
> ground to the end plate is as critical, more critical than the anode wires 
> connection.
I completely agree about the importance of the grounding. If I remember 
correctly, we were worried about connecting those 2 pins to the ground. 
Instead we are still looking into connecting the HVB ground to the 
end-plate in other ways (I believe Fernando's grounding rods and Al 
shielding would be a way to do it). Also here we have a point for the 
phone conference.


> A connector of 26 pins, single row, 0.156" would work well, use the two 
> end pins for the ground and use the middle 24 for your signals. Or, 
> perhaps better for reliability, if it fits which I imagine will not be a 
> big problem, use a 28 pin connector, 24 signals in middle, skip one pin 
> on each end (let it float on connector, have no/minimal contact pad on 
> pcb, not connected), and one ground pin on each end. This will give some 
> extra clearance against surface leakage or breakdown on the pcb board.
We should come to an agreement about what connector to use and find a 
better way to order them.

Cheers,
 	Yves