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FDC Weekly Meeting

Date: July 17, 2008

Participants: Daniel, Simon, Chuck, Beni, Elke, Brian, Fernando, Mark, Eugene, Bill, Micah, Kim, Roger

Next Meeting: July 24, 2008 @ 1:30 p.m.

Cathode Planning

 - Cathode delivery date is expected within roughly 2 weeks.
 - Our transport box has arrived at Allflex.  Due to our change in
   plans for the length of the boards, we need to provide Allflex with 
   instructions on how to prepare the shipment.  DSC suggested to have
   Allflex stack the boards and then roll up the naked ends on cylinders.
   Roger will communicate this to the Allflex representatives.  We will 
   modify this box upon arrival at JLab to include the ability to flow 
   nitrogen or dry air to prevent oxidation of the copper traces.
 - Fernando has received the probes for the electrical checkout and
   characterization of the cathodes and will work to put together a
   test plan document.  This should be ready for review next week.
 - Bill and Brian have begun discussing planning of how to cut the
   cathode board edges.  They will do some trial cuts with pieces of
   test Kapton and then converge on a procedure.  More details to come
   so stay tuned.
 - Roger plans on ordering a set of 3 to 5 of the new cathode daughter
   boards that we plan to use with the full-scale prototype.  We expect
   that with the copper fingers extending off the flex cable, that
   soldering to the cathode surface will be a very straightforward
 - Roger circulated the cathode board material specification sheets
   that we received for the material supplier.  DSC has asked Fernando
   for comments or impressions.
 - Due to the height of the solder connection between the cathode board 
   and the rigid flex assembly, we will have to revisit the design from 
   the standpoint of adding clearance pockets on the surfaces that mate 
   up against this solder region.  Chuck understands the issue and will
   work to make some pictures for us to look at.  We most probably will
   add thin pockets in the G10 frame skins to allow for the clearance.
   Once we get a look at some relevant design pictures, we can make sure
   that there are no issues with these pockets.  This work needs to be
   brought to conclusion in the next few weeks as we need to do the
   machining on the skins as part of the wire frame construction
 - Brian will modify his Lucite box design for storage of the completed
   cathode planes.  The cathode planes can stack upon one another
   (unlike the strung wire frames).  As this box is not needed for
   at least several months, this work is not super high priority.
 - DSC circulated a cathode R&D planning document to the group for
   feedback.  Brian and Simon are now going over this document to
   ensure that the task list is necessary and sufficient to complete
   our design work on the cathode construction procedure.  DSC will
   meet with Brian to go over this list.  Once we have a complete task 
   list, DSC will prepare a time line so that we can understand the 
   impact on FDC design completion and the start of construction.  This
   will also give us some clues as to manpower issues.

Full-Scale Prototype

 - The work on the assembly jigs is in queue in the JLab machine shop.
   The work should be completed in about a week.  Once the jigs are ready, 
   we will move to begin construction of the full-scale prototype wire 
   frames.  As  there is no money to spend on a new A-frame for the lifting, 
   Tim has investigated borrowing equipment already at JLab.  He has 
   identified two A-frames and we need to look them over to see if they will 
   work for us.  Brian will be in contact with Tim to have a look at the
   equipment.  Once we decide if they are useful for the FDC work, we
   can then work out a loan agreement.
 - The granite table that we ordered will be arriving August 1.  Another
   group will occupy the clean tent for the first week of August, and then
   we will take over.  Note that we expect the cathode construction work
   to take place in the clean tent and the wire frame construction work
   to take place in EEL 126.
 - Brian will work to prepare a wire frame construction document during
   the construction of the full-scale prototype frames.  This work should
   begin once we get the assembly jigs from the shop.  Due to R&D budget
   time lines, the funds for the Phase 2 wire winding have to be obligated
   before the end of September.  This mean that the prototype wire
   frames need to be basically constructed by the end of August.
 - We discussed a few remaining items that we need for the prototype.
   We need to provide Elke with a list so that she can understand the
   budget fully.
 - Elke said that she has a Ph.D. student available that she can assign
   to the FDC project.  This student could be responsible for HV testing
   of the wire frame circuit boards, cathode testing, full-scale prototype
   testing, etc.

Cathode Prototyping

 - Brian has been in discussion with some outside companies about
   our technique of joining the three separate cathode boards together.
   There are some important points that are coming to light:
   > The use of 2-in wide Kapton tape is certainly not be best
     joining material that we can use as there are much better adhesives
     out there.  We would be much better served to use Hysol adhesive
     on blank Kapton strips.  Brian is still digging up information
     on whether the improved strength is against peeling or sheer
   > The strength of the bond of neighboring boards will be improved
     if we use a wider strip of tape.  We may ultimately need to
     consider this.
   > The 20-in wide Kapton rolls that Allflex receives are sliced from 
     60-in wide rolls made by the material vendor.  Apparently it is
     the case that the tensile strength of the middle pieces have a
     different profile that the outer pieces.  Once the 60-in roll
     is slices up, they do not keep track of inner and outer pieces.
     This is problematic if we require a large tension to be applied
     to our 3-piece cathode.  The distortion of the electrodes would
     be different for the different pieces!  This would demand that
     we want the tension to be as low as possible.  This also could be
     a problem if we want to use a fixed weight to define the cathode
     tension.  With different tensile strengths in the different
     pieces, we could not guarantee a fixed tension.  Anyway, some
     things to consider as we move forward.
   > The key in all of this is how flat the cathode pieces from Allflex
     are.  In the past, our technique has been to apply enough tension
     to remove the wrinkles.  If the delivered cathode pieces are very
     flat, we are certainly in a much more advantageous position.  We 
     also eliminate the worry about stretching the cathodes if we can
     employ a low enough tension and also eliminate worries about the
     joints between boards pulling apart.
  - From the flatness measurements that have been made on our prototype
    cathodes to date, the version with the 2-mm thick foam backing will
    not work.  The bulging profile is too large.  This is presumably
    due to gravitational sag of the foam.  We are doing measurements now
    that will address this.  The apparent bulging that we have seen in
    the unbacked (tensioned) cathode may not be fully real in that the
    measurement system could not force the cathode to flat.  The bulging
    is like associated with a potato-chipping of the support frame under
    the tension load.
  - Brian has received a Kapton roll 48 inches wide.  We will use this
    to test various cathode construction techniques and to study methods
    of attaching the cathode to the frame.  Brian will work to develop
    a system to measure the cathode membrane tension while on the
    tensioning fixture.  This system will use the laser measurement
    head that we have for the flatness measurement system.  This process
    will begin setup within the next week.

Test Frame Wire Winding

 - The paperwork for the continuation of the Phase 1 wire winding
   contract with IUCF is finalized.  The agreement is that this
   work will be completed in full by August 22.  DSC and Keith are 
   finalizing the details of the work plans.  
 - The technique to scan the wire placement on the winding table before 
   attaching to the frame will use the technique of Moire interference 
   fringes of the wires and an overlaid mask.  The reference for this 
   work is H.B. Dijkstra et al., NIM 188, 59 (1981) (a wonderfully brief
   article). This technique is simple and fast and should tell us placement
   accuracy to easily better than 50 microns.  IUCF has requested that
   JLab provide the mask that is laid on top of the wires.  Keith will 
   provide details on what is needed before the end of the day and DSC 
   will work with Kim to see if the mask can be made at JLab.
 - DSC talked with Steve Christo about the quality of our Cu-Be
   wire.  He did not think that there was any reason to discard the
   existing sample and that using it in our prototype would not
   lead to any noticeable problems.
 - DSC is working with Steve Christo to prepare a wire specification
   document for the tungsten and CuBe wires leading up to procurement.
   Steve is preparing a document for the Hall B chambers and we will
   most likely adopt this document for Hall D.  DSC reviewed the
   existing Hall B documents to give folks a flavor of how these
   documents have been prepared in the past.  We need to make decisions
   on what is required for the FDCs.
 - As the time to complete Phase 1 and Phase 2 winding before the end
   of the fiscal year will be super tight, DSC will work with Elke to
   complete as much of the required Phase 2 paperwork as we can in the
   next few weeks so that we can move quickly to getting Phase 2 in
   place before time runs out.

Stack Assembly Procedures

 - DSC, Brian, Tim, and Bill will work to finalize the stack assembly
   construction document that has been prepared.  This document should
   be in place before we get too far in the construction process.

Cathode Flatness Measurements

 - Bill is working to finish the engineering design of the cathode
   flatness measurement system.  He will have some design drawings to
   walk us through at our next FDC meeting.
 - Micah will continue making measurements of the surface profile of
   our backed and unbacked cathode prototypes as a function of rotation
   angle.  He will also disturb the cathode surface and study repeatability
   of the measurements.
 - We need to work to define the allowable surface flatness variations
   for the cathodes.  What can we tolerate and still deliver a system
   that can meet the resolution requirements for the cathodes and the
   wire plane?  Eugene has volunteered to take this on.  Simon will
   pass along the relevant notes that he has to Eugene.

Cooling System Tests

 - Bill installed the flow valve in the cooling system in F117.
   Bill and Fernando will continue the cooling system tests this week.

Gas System Design

 - Vladislav (Slava) Razmyslovich is working on a preliminary layout
   of the gas handling system for the CDC and FDC in preparation for
   the upcoming systems review.  We will sit down with him in a
   specialized meeting to review the design concepts when we get a chance.

STB/HVTB Discussion

 - Kim needs to provide an instructional writeup for the Phase 1 and
   Phase 2 wire frame PCB component attachment.  This is on her to-do
   list, but is not a high priority for now.

Cathode Board Discussion

 - Roger needs to prepare a document for QA/stuffing/cleaning for the
   cathode boards and a similar document for the cathode daughter
   boards and ground boards.

Small-Scale Prototype

 - Simon and Fernando have taken some more Fe-55 measurements with the
   small-scale prototype in an effort to finalize the FDC dynamic range
   specifications for the anodes and cathodes.  Simon and Fernando should
   be able to complete the analysis of this new data within a week and
   Simon can then work to update the results document.  What we have so
   far is posted as GlueX-doc-1070.
 - We still have the lingering issue of the problematic x-y plots from the
   2-micron Cu cathodes.  Simon will revisit this problem by taking some
   new pulser calibration data to see if this makes the apparent problem
   go away.


 - 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.

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.