[Halld-tracking-hw] CDC Ground Connections

[Curtis A. Meyer]

Hi Everyone -

  the drawings that Slava posted today appear to have the ability to have a
"force-free" insertion and removal of the HV cards. I think that the only
requirement is that th screw used be captive so that it can also be used
for extraction.

    Curtis
wilkin wrote:
> Hi all,
>  
>     I just measured the insertion force multiple times and came up 
> with an average reading of 10 pounds.
>  
> gw
>
> ------------------------------------------------------------------------
> *From:* Tim Whitlatch [mailto:whitey at jlab.org]
> *Sent:* Friday, September 18, 2009 4:23 PM
> *To:* Gerard Visser
> *Cc:* cmeyer at ernest.phys.cmu.edu; GlueX Tracking; Gary Wilkin
> *Subject:* Re: [Halld-tracking-hw] CDC Ground Connections
>
> 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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>>   


-- 
Prof. Curtis A. Meyer		Department of Physics
Phone:	(412) 268-2745		Carnegie Mellon University
Fax:	(412) 681-0648		Pittsburgh PA 15213-3890 
cmeyer at ernest.phys.cmu.edu	http://www.curtismeyer.com/