[Halld-tracking-hw] CDC Ground Connections

[Tim Whitlatch]

Hi All,

In the current configuration, a 1/2 inch thick lexan (polycarbonate) 
plate will deflect approximately 2mm with a 20 lb force applied between 
the standoff positions. This can be reduced below 1mm if we double the 
number of central standoffs to 16. Data for the EDAC 307/357 series 
connector indicate that the force is more like 1 lb. If we increase the 
thickness of the lexan to 5/8 inch, we can reduce the deflection in half 
again.

Slava has posted layouts of some of the latest grounding schemes and 
support rods at;

http://www.jlab.org/~vgr/CDC%209-18-2009/

Please have a look.

Cheers,

       Tim

Curtis A. Meyer wrote:
> We will take the one board that we have here and measure it on Monday. 
> That
> should give is a pretty good idea. We would also like to try and 
> simulate the deflection
> of that force on a piece of Lexan.
>
>   Curtis
> Tim Whitlatch wrote:
>> How much force do we anticipate on making these connections?10lbs? 
>> 20lbs?
>>
>> Tim
>>
>> Gerard Visser wrote:
>>> Hi Curtis,
>>>     I endorse completely your comments regarding deflection and 
>>> reliability! There should either be more mechanical support (which 
>>> could serve as a ground connection, or not) or else there should be 
>>> attention to make an insertion/extraction tool and features in the 
>>> design to insert/extract the HVB without applying too much force 
>>> that strains the wire connections.
>>>     For the wire pin to the ground sockets, for instance there is 
>>> http://www.mill-max.com/pdf/datasheet/pin_rec_catalog/8000-0-01-15-00-00-03-0.pdf 
>>> if you would be able to use a #19 or #20 wire. It is just slightly 
>>> too small for #18. But IMHO it should be enough - unless there is a 
>>> mechanical consideration about the wire diameter passing through the 
>>> gas seal that I don't know about.
>>>     Sincerely,
>>>
>>>         Gerard
>>>
>>>
>>> Curtis A. Meyer wrote:
>>>  
>>>> Hi Everyone -
>>>>
>>>>      a couple of points on the grounding connection.
>>>>
>>>>     Sometime ago, we had proposed "continuing" one of the legs that 
>>>> supports
>>>> the connectors for the HV-boards through the gas plenum to the 
>>>> endplate. This
>>>> standoff would then serve to both support the HV connector and 
>>>> provide a solid
>>>> ground connection to the end plate. The one concern is that it 
>>>> might not be possible
>>>> to place one support for each connector such that the feed through 
>>>> can carry through
>>>> to the end plate.
>>>>
>>>>     Assuming that the above is not possible (which we still feel 
>>>> would be the best grounding
>>>> and support scheme), then we are worried that there are not enough 
>>>> stand offs in the current endplate, there are only eight as far as 
>>>> we can tell in the current design.
>>>>
>>>>     We are very concerned that there are not enough standoffs to 
>>>> support the swiss cheese
>>>> plate, particularly during insertion and removal of the 
>>>> high-voltage cards. What we see with
>>>> the models that we have at CMU is that the force needed to insert 
>>>> and pull the card is
>>>> sufficient to actually compress or pull-out the plastic plates. The 
>>>> way the connection
>>>> scheme now goes. This distortion becomes a force either directly on 
>>>> the crimp pin,
>>>> or on the glue joint that seals the chamber. These have the 
>>>> potential to break wires
>>>> in the straws or break the gas seals every time a HV board is 
>>>> changed.  It is important
>>>> that additional standoffs be added, either during or after 
>>>> manufacture of the Al endplate.
>>>>
>>>>     Finally, assuming that we adopt Fernando's connector, we need 
>>>> to know if there is a
>>>> source of the .020 male part that can be soldered to the .040 wire 
>>>> and is inserted in the
>>>> press-fit hole. The connector itself is quite slick and the 60gm 
>>>> force needed to engage
>>>> it seems fine. But the male part is equally important to this working.
>>>>
>>>>
>>>>      -- Curtis
>>>>
>>>>  
>>>>     
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>>>   
>
>