[Halld-tracking-hw] CDC Ground Connections

[Gerard Visser]

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
> 
>   
>