[Halld-tracking-hw] CDC feedthrus and end plate

[Fernando J. Barbosa]

Hi Gerard,

Perhaps this threaded socket 
(http://www.mill-max.com/pin_rec_catalog/productInfo.cfm?webpartnumber=4947&start=1&leaddiameterrange=%2E032%2D%2E046&pin_or_rec=rec&PartDescription=Threaded%20Receptacle&taildiameter=&tailtype=&mountingfeature=&mountinghole=&bodylength=&search=&pr=rec&stagecode=)  
will work. There are also threaded pins (not from Mill-Max).

Best regards,
Fernando

Fernando J. Barbosa wrote:
> Hi Gerard,
>
> Press-fitting the socket into the Al plate looks like a good idea but 
> I am concerned about the quality of the connection over time. Perhaps 
> having a slightly oversized hole and using conductive epoxy, followed 
> by Humiseal 1B31 or 1B73 on the surface would prevent corrosion on the 
> interface (using the closed socket part #).
>
> The ground wire needs to be insulated because the straw interconnect 
> cables, although insulated with PVC, are at HV. However, it can be 
> solid to plug directly into the socket but I have some reservations, 
> and you point these out, as to the cut/finish of the wire. I favor a 
> crimped pin.
>
> Best regards,
> Fernando
>
>
> Gerard Visser wrote:
>> Hi Fernando and Tim,
>>     Please consider as I mentioned the use of a pressfit pin socket 
>> in the endplate if space is at a premium. [Well, ok, I think we know 
>> that is true...] I don't know if this is really practical in 
>> aluminum, it certainly works in printed circuit boards. I think it 
>> would be relatively easy for you to make some tests, if you can 
>> afford to delay releasing the endplate drawings for a little while yet.
>>     Consultation with Mill-Max (or other vendor) might give a more 
>> accurate judgement of which socket to select and whether it will 
>> work. But naively I think - trying to stay small - that for instance 
>> Mill-Max # 0252-0-15-15-32-27,
>> http://www.mill-max.com/pin_rec_catalog/productInfo.cfm?webpartnumber=0252&start=1&leaddiameterrange=.015-.025&pin_or_rec=&PartDescription=Receptacle%20With%20No%20Tail&taildiameter=NONE&tailtype=NONE&mountingfeature=PRESSFIT&mountinghole=0.057&bodylength=&search=&pr=Rec&stagecode= 
>>
>>  pressed into a (round) hole 0.057+/-0.002 x 0.150 min depth (not to 
>> break through, of course), and located anywhere that there is 0.080 
>> diameter clear area on the outside surface of the endplate, would do 
>> nicely. If you can find 152 such appropriate locations for this, one 
>> near each preamp connector. We can certainly find a ~0.020 diameter 
>> pin to crimp or solder on the ground wire, to plug into this socket.
>>     I just think that this might be easier to accomodate than tapped 
>> holes, and also easier to actually install the ground wires. Of 
>> course, a lug under a screw is probably a better connection, so if 
>> there is room for that I certainly don't want to dissuade you from 
>> that approach.
>>     Use of the pressfit pins should certainly be conditional on some 
>> tests to see how they go in bulk aluminum, which is not their usual 
>> application. And also probably to optimize the diameter. Also of 
>> course, this approach would add an additional setup and processing 
>> step to the endplate production, must cost a little.
>>     Please consider it, unless you have a reason to rule this out 
>> immediately.
>>     Sincerely,
>>
>>         Gerard
>>
>> ps. The ground wires can be solid bare wire (#16 - #22), no? That 
>> seems the easiest to me. [And actually #22 solid wire can be plugged 
>> right into this socket, assuming it is cleanly cut; if using 
>> tin-plated wire then the contact should be changed from gold to tin, 
>> also a standard option - but leave the body plating gold. Bare copper 
>> might be preferable though. Or a slightly larger pin for #18, e.g. 
>> 0334-0-15-15-34-27-10-0. Maybe that is the way to go, looks even 
>> better.]
>>
>> Fernando J. Barbosa wrote:
>>> Hi Gerard and Tim,
>>>
>>>     I am in agreement with Gerard. I have always made the point that 
>>> the shorter the connection (any) the better and distributed 
>>> throughout the end-plate. Slava has also made the point that a 
>>> direct connection (say, a stud through the gas plenum) would be 
>>> impossible due to the density of the straws and the location of the 
>>> preamp card connectors.
>>>     Ground wire (16 AWG w/FEP insulation?) connections in a regular 
>>> pattern will work better than the peripheral connection attachment. 
>>> Of course, the quantity of these connections will need to be 
>>> determined but I agree that we should make provisions for as many as 
>>> possible even if not used in the final configuration. I have not 
>>> looked at the latest drawings in detail but I requested a large 
>>> number of blind taped holes throughout the endplate when we were 
>>> considering different alternatives to the straw connections in the 
>>> past - maybe these were dropped along the way.
>>>     The grounded disk is supposed to be copper and there are no 
>>> major constraints on the thickness, other than cost. But this is 
>>> already an expensive disk due to all the machining that will be 
>>> required.
>>>     Therefore, if there are no mechanical strength issues on the 
>>> endplate, let's add the taped holes throughout the endplate and make 
>>> the connections as Gerard suggests.
>>>
>>> Best regards,
>>> Fernando
>>>
>>> Gerard Visser wrote:
>>>> Hi Tim,
>>>>     Yes, I know. This (152 direct lines) is what I had in mind. 
>>>> Maybe it is too much to ask for. Your question whether we can live 
>>>> without it is a good one, wish that I (or Fernando) knew the answer 
>>>> 100% for sure. *Perhaps* the answer is yes. If I had to guess, I'd 
>>>> say better than even odds.
>>>>     One the other hand if you could for instance add the 152 
>>>> features (4-40 blind taped hole? or a blind hole to fit a Mill-Max 
>>>> press-fit pin socket? or something like this?) to the endplate, 
>>>> then if the eventual answer turns out to be no, it does not mean 
>>>> the finished, and I imagine rather expensive, endplate is unusable.
>>>>     It was the absence of any such features as far as I could 
>>>> understand in your drawing, that stimulated this discussion.
>>>>     If it is simply impossible to have 152, or even 152/2 or 152/3 
>>>> or 152/4 by some sharing scheme, then we must risk doing without 
>>>> it. If it is possible, my opinion is the features should be added, 
>>>> they can always be left unused if it turns out that we don't need 
>>>> them, i.e., if grounds around the outside will not suffice.
>>>>     By the way, the boards will (I really hope) be sitting on a 
>>>> ground plane, e.g., the upstream plenum is a sheet of thin 
>>>> aluminum, right? Because I can pretty much guarantee you that 152 
>>>> preamp boards with each a skinny 40 cm ground wire between the 
>>>> preamp and the endplate, this will not work. If the connection is 
>>>> through a common sheet of (preferably plated) aluminum, it stands a 
>>>> good chance but I would still be nervous that the direct (152 5cm 
>>>> lines) plan might prove to be necessary.
>>>>     Well, I think we should consider this more and you'll have to 
>>>> tell what you can really do. But the shorter, wider, more 
>>>> distributed the ground connections are, the lower the risk and 
>>>> potentially the better the performance. We must not forget this :)
>>>>     Sincerely,
>>>>
>>>>         Gerard
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