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FDC Weekly Meeting

Date: July 10, 2008

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

Next Meeting: July 17, 2008 @ 1:30 p.m.

Cathode Planning

 - Cathode delivery date is expected in roughly 2 weeks.
 - Roger will contact Allflex to have them let us know when the transport
   and storage box has arrived.  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 been thinking about the electrical QA checkout procedures
   for the cathodes.  He has ordered some probes for this work.  He will
   prepare a procedures document and circulate in the next week or so.
   We expect that this work will be carryed out in the clean tent using
   the new granite table that should arrive on August 1.
 - We discussed a plan for precision edge cutting of the cathodes.  Bill
   and Brian will sketch out a plan for how to proceed.  Once we are all
   satisfied, we will do some test cuts on pieces of the dummy cathode
   boards and pieces of blank Kapton.
 - 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 is working with the Allflex representative to find whatever
   information is available from Nippon on the raw material specifications.
   He has gotten some information through Allflex and will circulate this
 - 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 is responsible for looking into
   this and letting us know.  He will get on this after his committments
   for the CD-3 review are done with.
 - 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.

Full-Scale Prototype

 - The work on the assembly jigs is in queue in the JLab machine shop.
   The work should be completed by the 3rd week of July.  Once the
   jigs are ready, we will move to begin construction of the full-scale
   prototype wire frames.  At some point in the near future, we will
   need a crane (A-frame) for lifting of the tooling plate.  DSC will
   talk to Elke about this.
 - The electrical work to connect the clean tent to power has been
   completed.  Another group will be using the space for about a
   week during the last week of July.  However, given that our granite
   table does not arrive until August 1, there should not be a conflict.
 - Brian and Bill will work to update our wire frame construction sequence
   document.  Brian will provide a first draft to Bill who will work to
   polish it up.  We would like to provide this to Casey so his group
   (and of course ours) can full understand the procedures.  This work has
   not yet gotten underway.

Cathode Prototyping

 - 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.  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.
 - 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 gravitation 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 full 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 ordered a roll of Kapton 48-in 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.

Test Frame Wire Winding

 - The paperwork for the continuation of the Phase 1 wire winding
   contract with IUCF should be completed this week.  DSC and Keith
   are finalizing the work plans.  Work should continue next week.
 - We need to make a decision on whether to purchase new Cu-Be wire
   given the defects that we saw under the SEM.  DSC will talk to
   Elke about budgets on this.
 - 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.

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

 - 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?
 - Bill has looked at our cathode flatness system and is not satisfied
   that it can deliver anywhere near the accuracy that we require.  He
   will work to re-engineer the system using existing pieces, pieces that
   we can dig up at JLab, and new pieces.
 - Micah and David put together a list of parts 'n pieces for the
   measurement system upgrade.  DSC has worked with Lorelei to order
   the parts.  They should arrive in a week or two and then the
   upgrade work on the system will continue.

Cooling System Tests

 - Bill installed the flow valve in the cooling system in F117.
 - Fernando has completed a series of tests of the cooling system
   as a function of the temperature setting of the water reservior
   for fixed flow rate.  A flow control valve has just arrived an
   will be installed next week.  The plan is to perform more cooling
   studies as a function of flow rate for fixed temperature.  Fernando
   will prepare a GlueX note when the studies are finished.

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 is continuing his work to specify the ASIC dynamic range.
   He has taken lots of data with the small scale prototype and has
   completed a series of simulations using GARFIELD to connect the
   cosmic ray and X-ray source data to what we expect with pions and
   protons.  So far he has been able to use GARFIELD to reproduce
   the chamber data with cosmics and X-rays.  He will now work to
   specify the dynamic range for cathode and anode and update the
   draft of the associated report.  This work is posted as 
 - Fernando has suggested taking some data with a 90-10 Ar/CO2 mixture
   to ensure that we fully understand the 55-Fe data and to allow an
   easier connection with the CDC data.  The 90/10 gas mixture is now
   flowing in the prototype and Simon is beginning to take some data.
 - 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.
 - Also folks should send DSC the latest design drawings where there
   have been changes to keep this web site up-to-date through the
   review season.

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.