Minutes 9-12-2007

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FDC Weekly Meeting

Date: September 12, 2007

Participants: Daniel, Simon, Chuck, Tim, Kim, Roger, Fernando

Next Meeting: September 19, 2007

Composite Wire Frame

 - The machine shop has finished drilling the through-holes and o-ring
   groove in our two composite frames.  Brian filled the o-ring groove
   with epoxy and the machine shop then completed the machining of the
   o-rings.  With the first frame, Brian poured in the epoxy (low
   viscosity variety) with a squeeze bottle.  He noticed that the epoxy
   flowed under the g10 skin by several inches all around the groove.
   On the second frame, he sealed the face of the Rohacell and then
   filled the groove and did not notice any epoxy flow under the g10
 - Brian will start next week to do the load test on the wire frame
   that has our nominal dimensions to study the deflections and to
   look for failures. 
 - DSC will take some pictures of the frame for the upcoming DOE
   FDC report.

Composite Cathode

 - No work done yet.  Brian will get to this soon.


 - Kim has nearly finalized the layout of the dummy STB, HVTB, and
   side boards for the FNAL wire winding that is slated to begin next
   month.  She circulated drawings of all the boards before today's
   meeting and got feedback and implemented the suggestions.  In our
   design all neighboring boards will overlap each other to give us
   improved strength in the design.  The overlap region is basically
   a half-lap design of width about 5 mm.  
 - We discussed the tolerances required and the fabrication notes and
   came to conclusion on all of this.
 - Kim will circulate final drawings tomorrow and after we all sign
   off on them, she will prepare the drawings for the board house.

Magnetic Field Tests

 - All network and DAQ problems seem now to be solved.  DSC and Simon
   have finalized the trigger timing and Simon has taken a few runs
   to make sure that we are seeing sensible data from the MWDCs and
   the chambers.  This work is still in progress.  Once this is
   finalized, then Simon will calibrate the gains of the cathode
   readout.  The plan is to take a long B=0 run over the weekend.
   The coincidence event rate is about 0.1 Hz (which is similar to
   the rate that Simon had in the Test Lab).

Small-Scale Prototype

 - Brian has not gotten to the mounting of the +/-75 deg cathode
   boards.  He has everything he needs to do this work, but has not
   had time.  He will get to this soon.

Cathode Rough Out

 - Roger has done some work to study the cathode design including a
   hole in the middle of the board.  His layout now includes an
   8 cm diameter hole.  In this design, only about 12 or 13 of the
   strips are affected by the hole.  However in order to ensure that
   our readout remains quantized in units of 24 channels, we have
   decided to split 6 strips on either side of the hole.  This gives
   us a total of 9 connectors on each cathode plane.  The splitting
   of a few extra full length strips will help with the rate problems
   on these strips that led to higher occupancies than desired.
 - This new design will ensure that our two cathode designs (6 cm
   diameter hole and 8 cm diameter hole) will not impact the number
   of readout channels on the different cathodes.

Cathode Board Readout

 - After Roger completes the cathode design including the hole, he
   will work to complete a design for the cathode readout.  The plans
   are to include a cut out in the cathode support frame through which
   a flex cable will be fed that connects to the daughter board
   connector.  After we have a design, he will work to make a prototype
   to test and optimize the design.
 - In our current FDC design, we have a space of 1 cm between neighboring
   cathodes in order to have room for the daughter board connectors.
   DSC wants to eliminate this space and have the neighboring cathode
   frames in direct contact.  With the old design, we had to add an
   extra spacer ring between the cathodes to give us o-ring compression.
   We discussed a plan for the design that would mount the daughter
   board connector on the back side of the 1/32-in thick G10 skin.  If
   we need these frames to be thicker to accommodate the connectors, we
   can simply use a thicker piece of Rohacell.

DOE Report

 - DSC has begun work on the DOE FDC report.  The text is essentially
   finished and the document is missing some photographs and Monte
   Carlo plots.  Folks will be contacted if needed to provide help.
 - DSC has been in contact with David Lawrence and he is working to
   provide the necessary Monte Carlo figures.  The report is due to
   Elke at the end of next week.

Work List

 - The FDC short-term work list has been posted on the FDC web site
   (see http://www.jlab.org/Hall-D/detector/fdc/).  This is continually
   being updated and DSC welcomes any feedback or comments from the group.

Minutes prepared by Daniel. Send any comments or corrections along.