Re: Chamber Infrastructure

[Paul Smith <ptsmith@indiana.edu>]

Hello Ravi,

On Mar 15, 2004, at 6:13 PM, Ravi Kiran Anumagalla wrote:

>
>  I have come up with two models for supporting the drift chambers  
> inside the calorimeter.
>
>
>  Hence we have a gap of 10 cm to support the CDC,FDC and would need to  
> have enough space to accommodate the cables being removed from the  
> upstream end of CDC.

>  DATA Required:
>
>  If I have the exact number of cables which needs to removed from the  
> front end (upstream end) I could modify the dimensions of the fiber  
> glass chambers to suit the space requirement.
>
>
>  pls. give me your comments, so that I can modify/improve the current  
> 2 models which I have proposed.
>


If you look at page 203 of the version 4 GlueX design report there is a  
summary of the numbers of channels for the various detectors.  I can  
tell you that the forward and barrel calorimeters, the cerenkov, and  
the time-of-flight will most likely use RG58 coax for the signals.  The  
central drift anodes and forward drift cathodes will most likely use  
ribbon cable coax; this typically has 16 very small coax cables per  
ribbon; one manufacturer is AMP.  The TDC signals will likely be on  
twisted pair ribbon cables; this typically has 16 pairs per ribbon.   
AMP also makes this type of cable, although there are many sources.   
I'm sure you can find examples of these types of cable at JLab.

I think it would be very useful to start including cables in your  
models.  There is also plumbing for the target which needs to be  
included.

If you look at page 191 of the v4 design report, there is a paragraph  
about cabling.  We would like to operate the detectors in the extracted  
position; this implies either some sort of cable loops with a way to  
manage the extra cable, or that the electronics moves with the  
extracted detectors.  Having the electronics located as close as  
possible to the detector and moving during extraction is my preference  
since this minimizes the total cable length.  My understanding is that  
this is done in hall B when the CLAS detector is opened.  Page 203 of  
the design report also summarizes the number of electronics racks  
required.  I showed an oversimplified cartoon of this at the meeting  
last December; you can see it at:

http://www.jlab.org/Hall-D/meetings/coll_dec2003/talks/ 
Paul_Dec_2003_collab.ppt

Extracting the forward drift chambers from the back of the magnet  
implies the FDC cables also exit from the back of the magnet.  This may  
be a problem with acceptance - hermeticity is essential for the GlueX  
physics; this needs to be looked at carefully in the simulations; to  
the best of my knowledge none of the simulations to date include  
cables.

Please don't hesitate to ask me questions,

Paul Smith