Minutes 12-20-2007

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FDC Weekly Meeting

Date: December 20, 2007

Participants: Daniel, Brian, Simon, Roger, Kim, Chuck, Fernando, Bill, Mark

Next Meeting: January 3, 2008 (tentative)

Composite Wire Frames

 - Five composite wire frames have been made.  Three of these will be
   selected to move on to the JLab machine shop to add the through holes
   and the o-ring groove.  Two will have low-density Rohacell and one
   will have medium-density Rohacell.  They should be ready to send off
   for wire winding by the third week of January.
 - The Lucite storage and transportation box has been delivered and looks
   quite nice.
 - Brian has come up with a design for the wire frame strong-back and we
   suggested a few minor changes that Brian will incorporate.  He will
   pass this on to the JLab machine shop in early January for construction.
 - With the development of the alignment/construction jig last month, we
   believe that we have finalized the composite wire frame construction
   procedure.  This procedure will be document in January of next year.

Wire Stringing

 - A signed statement of work from IUCF was delivered this morning.  The
   total wire winding project cost for all 3 phases (test winds, prototype
   winds, and production winds), including contingency and overhead, came
   in at under $120k.  DSC has completed a sole source declaration for
   the work and passed it onto Elke.  Elke delivered all paperwork to the
   JLab procurement folks and it looks like we will have a signed contract
   in place by the end of January (if all goes according to plan).  It
   might even be possible to start the test winds by the end of January.

Cathode Boards

 - In our current nominal design, each active chamber layer is supposed
   to be an isolated gas volume.  Due to the need to minimize material
   in the active area of the FDC, we reduced the Rohacell foam backing
   from 5 mm to 2 mm.  Thus there is a gap between the Rohacell backing
   and the ground plane.  We have calculated that the deflection of
   the cathode due to the small positive gas pressure in the chambers would
   cause the cathode to deflect by too much.  We have decided therefore
   to make each FDC package a single gas volume.  This change is relatively
   straightforward in that we will allow through holes in the cathode
   boards (either at the edges or the center -- or both), and holes in
   the Rohacell backing.  This will equalize the gas pressure across the
   cathodes.  The only remaining issue is the end layers on each package.
   Here will we follow the same plans, but now our outside ground plane
   will become a gas window.  This window is allowed to deflect without
   affecting chamber performance.  Our inner ground layers are made from
   6.3 micron thick aluminized Kapton.  This will not be sufficient
   for the end gas windows.  Bill will calculate what the design of these
   gas windows will have to be.

Composite Spacer

 - Brian will work on making a prototype composite spacer in January so
   that we can finalize the design and construction procedures.  It looks
   like we will need to only make one spacer as the procedures are very
   similar to those for construction of our other composite frames.


 - Kim continues to make progress on the STB and HVTB designs.  We verified
   yesterday that we will have sufficient room on the STBs to lay out all
   of the signal traces.  Kim has all of the information needed to complete
   the designs.  They should be done by the second week of January.  We
   plan on submitted the boards to procurement before January is over.
 - A few specific items were discussed over the past week related to the
   wire frame circuit boards.  One is that we will include strain-relief
   pieces on the HVTBs for each of the HV baby cables.  Fernando has
   finalized the foot print of these glue-on plastic pieces.  We are
   also finalizing the connectors for ground attachments to these boards.

Wire Frame Issues

 - Brian has completed making five composite wire frames.  Three of these
   will be sent to IUCF for winding.  On one of the remaining two, Brian
   will install our prototype gas ports to finalize the attachment scheme
   and to make sure that they are robust enough given the handling that
   they will endure.
 - Brian will also contact Karen Kephart at FNAL at some point in January
   to touch base with her.  We will need some support/advice from the
   FNAL folks and we need to communicate with them that we will not be
   doing the wire winding at FNAL.

Cathode Daughter Boards

 - Roger will complete placing all orders this week for the parts and
   pieces needed to build a prototype of the cathode daughter boards and
   to develop and test the techniques of attachment to the cathode boards.
   For completeness, these circuit boards are relatively new to the FDC
   design.  The scheme to readout the cathodes is via a rigid flex cable
   soldered to the cathode board.  This flex cable feeds through a cut-out
   in the G10 cathode support skin through the cathode frame to the back
   side.  This flex cable is then soldered to the cathode daughter board.
   This board contains the daughter board connector and the necessary
   daughter board addressing resistors.
 - Roger expects that he will have the prototype completed by the end
   of January.  We can then finalize the design with whatever modifications
   are necessary.
 - Note that due to the combined thickness of the cathode daughter board,
   the daughter board connector, the daughter board and its components, we
   may have to increase the thickness of the Rohacell core in the cathode
   frames to allow sufficient clearance between neighboring cathodes to
   fit everything in.  This is a very minor issue that has no real
   impact on the work.  We will finalize the final Rohacell core thickness
   in the cathode frames in early January.


 - DSC has collected all of the available FDC subsystem design drawings
   and placed them on the FDC website.  The URL is:
   http://www.jlab.org/Hall-D/detector/fdc/drawings.html.  Folks should
   go through the drawings and let DSC know what drawings and/or categories
   are missing for a complete design set.

FDC Mounting System

 - Bill has been charged with designing the FDC mounting system.  He
   has several ideas for the mounting system, including rails and hard
   points mounted to the inside face of the BCAL.  He will continue to
   think about the design and present them to the group at some point
   early next year so that we can converge on our plans.

Cooling System Update

 - Bill has now finalized the positions of all cathode and anode daughter
   board connector positions and has completed the nominal layout of the
   cooling system, at least in terms of the on-chamber aspects.  Starting
   next year he will work to complete the off-chamber aspects of the 
   cooling system.

Upcoming Work

 - In January, Brian will complete the construction of a composite cathode
   frame.  There are still lots of issues to be worked out, such as how
   to align and attach the cathode boards (remember we have three circuit
   board pieces to make up each cathode).  It will most likely be the
   case that we will make several sandwiches before we optimize/finalize
   the construction procedures to ensure that we meet all specs.
 - In January, Brian will mount the +/-75 deg cathodes to the frames for
   the small-scale prototype.  There are two issues here that we need to
   test.  On is the improvement in the resolution with the +/-75 deg
   cathode orientation relative to the current +/-45 deg design.  This
   we already believe that we understand from calculations (but we need
   to verify).  The second issue, which is perhaps the more important, is
   that these new cathodes are made with a copper thickness of 2 microns,
   which is our nominal design choice.  All current cathode boards in the
   small-scale prototype have been made with a copper thickness of 5 microns.
   We want to verify the performance of these boards before beginning
   procurement of the cathodes needed for the full-scale prototype.
 - Brian has given Denny Insley the responsibility of making up several
   cathode frames that Brian will use to make our prototype cathode
   sandwiches.  Denny will also work to reorganize our space in the EEL

FDC ASIC Testing

 - Simon and Fernando have connected one cathode and one anode daughter
   board (with our ASIC preamplifiers) to the small-scale prototype.  They
   saw beautiful signals with very low noise.  This is quite in contrast
   to the problems encountered by the CDC folks.  Simon will take some
   long data runs with cosmic rays at the start of the year to do some
   higher-level analysis.  One problem encountered is that the gains in
   the system are so high, there is significant clipping of the pulses.
   Fernando will work with Gerard to modify Gerard's shaper boards to 
   remove the clipping problems.  Fernando has prepared a document detailing
   what tests we need to complete to provide sufficient feedback to Mitch
   for the next round of the ASIC design.  Simon will carry out this
   test plan in January.

B-Field Data Analysis

 - Simon has been working to calibrate the tracking data from the
   B-field test run completed this fall.  So far he has been working
   on determining all geometric offset parameters and to calibrate the
   time to distance relations for our two different gas mixtures.  Simon
   is expected to have results to compare against our expectations for
   the magnitude of the Lorentz effects in the first part of January.

Cathode Flatness Measurements

 - Brian will make it a priority in the first part of the month to
   develop a final scheme for measuring the flatness of our cathode
   boards.  We do not believe that we need to perform these scans with
   the cathodes in a vertical position.  Bill had some possible leads
   on a laser measurement technique.  He will do some research and get
   back to us.
 - Brian will contact CCT Marketing in January to begin a dialog with
   them regarding our specs for flatness of the delivered boards.  We
   also need to discuss with them how we want the boards shipped to
   us so that they don't come to us all banged up.  JLab may have to
   provide shipping containers.  We shall see.

Progress in 2007

 - The design of the FDC system for the GlueX experiment in Hall D has
   come a very long way in the past year.  DSC personally thanks each
   person who has been working so hard over the past year to get us
   to this point.  Your time, energy, enthusiasm, and efforts are very
   much appreciated.  We still have a long way to go, and DSC looks
   forward to finalizing the FDC design over the course of the next
   9 months with you.

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.