Minutes-10-2-2008

FDC Weekly Meeting

Date: October 2, 2008

Participants: Daniel, Simon, Mark I., Roger, Eugene, Bill, Micah, Herun, Jim, Beni, Elke

Next Meeting: October 9, 2008 @ 1:30 p.m.

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Full-Scale Prototype Updates

 - Clean Room:
    * In order to move out of the shop into our own space, we have been
      doing work on the wire frame construction using the granite table in
      the clean room.  Hence this space is not so clean at the moment.
 - Procurements:
    * Roger has not finished the design work for the cathode rigid-flex 
      assemblies.  The final number of these boards to be ordered (roughly
      70) has yet to be finalized.
    * Elke asked us to prepare a spreadsheet listing all expenditures for the
      full-scale prototype.  Kim has prepared a draft of this, but she still
      needs input from Brian, Roger, Lorelei, Simon, and anyone else who has 
      ordered parts n' pieces.  Please take a look at the existing document
      and provide feedback to Kim with your questions or comments.
    * Brian was working on the procurement of the sense and field wires
      for the full-scale prototype.  DSC prepared two documents for our 
      wires: Wire Specifications Document and Wire Testing Document.  
      These documents have been passed on to the wire suppliers.  More discussion 
      on this when Brian returns.  As of today, Elke received and signed the PR 
      for the sense wire and it was not clear if the PR for the field wire has been
      passed on to her.
 - Storage: Kim has been amassing various and sundry FDC-related components in
   her area.  She will bring them over to Simon for storage in F117 when she
   gets a chance.  DSC will talk to her about creating and maintaining a database
   for the FDC components to try to keep ourselves organized.
 - Bill is working to put the local HV connectors selected by Fernando into 
   the 3D CAD model and to detail how they will be attached (as they are 
   quite massive).  Bill will get back to this work when he has a chance.
 - It turns out the Greg Arnold's group will be able to acquire a programmable
   solder station that will allow temperature vs. time profiles to be set.  This
   will be perfect for the Phase 2 component stuffing on the FDC circuit boards.
   DSC will talk to Kim about finalizing the assembly/cleaning document to include
   this information (Fernando will be able to provide Kim with the information
   that she needs).

Cathode Planning

 - Mark got the nitrogen flowing through our cathode box using the dewar that
   Brian ordered.  We should have just a trickle of gas going through and the
   box has been purged of air.
 - The W&M SEM group did some study of a small piece of our sample cathode
   board from Allflex.  This sample was one that was stained with some sort of
   surface contamination.
   Their mass spectrometer analysis revealed only copper.  This is at odds
   with what Fernando found, which is that this contamination appears to be
   non-conducting.  Fernando is now working to do some additional measurements
   to resolve this apparent discrepancy.  More soon.
 - DSC wants to delay the ordering of the remainder of the cathodes for at least
   a few months.  We should work our way through the cathode R&D plan and work
   out all of the mechanical issues and final tension settings.  If the required
   tension ultimately causes any distortions (i.e. stretching) of the cathodes,
   they we might want to scale the artwork in the next batch.  We discussed this
   again and everyone is in agreement.  Roger will contact our Allflex
   representative to touch base and give them full details on our plans.
 - Bill has not done any more work on the system to cut the cathode edges.
   More to come when he gets back to this.
 - Holes, holes, holes:
     * We are still pondering deeply whether we will include the central
       Kapton beam hole in the cathode boards and whether we will include
       the side gas holes.  Bill is convinced that the perimeter gas holes
       in the frame are sufficient.
     * Eugene's preliminary FCAL rate studies show only a modest improvement
       if the Kapton in the central beam region is removed (of course in
       all scenarios there is no Cu in the beam area).  These calculations
       are being followed up by Sasha (Eugene has been in contact with Sasha
       since the end of the Collaboration meeting).
     * Bill and Mark will do a series of test cuts with our cathode prototypes.
       Bill used a punch to make a roughly 1-in diameter hole in one of our
       cathodes (a picture of this cut can be seen on one of the slides in
       Simon's Collaboration Meeting talk for those interested).  The cut looks
       good and the edges look good.  A larger size punch (about 8 cm in diameter)
       has arrived from Allflex.  Bill is already worried about how to apply the
       large forces needed to punch through the material. We will work on details
       when he gets back.
     * The nominal plan as of now is to set the cathode tension on the
       boards and then to add the central hole.
 - Please consult regularly the cathode R&D plan to better understand the 
   order and the time assignments.  Contact DSC with questions.
 - Cathode flatness measuring system:
     * The system assembly is now complete and Micah has hooked up the motors.
       He is running through system checks now and has identified a problematic
       limit switch on the vertical motion.  A dry fit of one of our cathodes
       prototypes has been completed.  We should not be too far away from doing
       a series of flatness measurements on our cathodes.
 - Brian and Bill should begin to layout a detailed outline for the cathode
   construction steps and circulate for feedback.

Wire Frame Construction

 - We have run into a problem when making the G10/foam laminates for our wire
   boards.  We had planned on using low-density 31HF Rohacell, and based on
   the R&D work completed by Brian, it seemed that this material would be
   satisfactory.  It turns out that its thickness is not well enough controlled
   and it is far too soft and floppy to make it through the manufacturing process
   without compressing.  Bill gave us an update talk on what he and Mark have learned over 
   the past week or so.  It is clear that 31HF will not work.  There are other
   higher density, stiffer versions of Rohacell out there that could work 
   (e.g. 110HF), but Bill will do some digging to find out more.  Simon will
   also do some radiation length computations to understand what we can afford
   in terms of materials.  Bill suggested using a solid 5-mm annular region 
   behind the wire boards as a precision spacer.  This could be too much of an
   impact for photon conversions.
 - The working specification on wire frame thickness is 5 mm +/- 2 mils (how's that
   for mixing units).  This spec will not be achievable with a foam core.  But
   given that our specification on the cathode flatness is about 4 mils, it makes
   so sense to have a much tighter tolerance on the wire frame thickness.  Our
   short term hope for a solution is that by changing from 31HF Rohacell to
   110HF Rohacell (or something like this) along with relaxing the thickness
   control specification, we may be able to produce a wire frame that will work for
   the FDC.
 - All wire frame circuit boards have had their modifications completed and are
   now back in our possession and ready for frame construction.
 - We are presently planning on borrowing an A-frame for EEL 126 for the
   wire frame construction (that Tim arranged).  No other frames could
   be found in storage that we could claim.
 - The most recent modifications to our aluminum jig plates has been completed
   by the machine shop.
 - DSC will arrange for the wooden shipping box now at IUCF to be shipped
   back to us so we can use it for the full-scale prototype frames.
 - PCB updates:
     * Kim has finished the moving of the decoupling capacitors on the back 
       side of the STBs. Fernando is now looking over the design drawings to 
       make sure all is well.  
     * The updated PCB drawings will be given over to Bill so that they
       can be put into the 3D model.
     * The PCBs for the FDC will need to be handled by all folks involved 
       with more care.  Many of the boards have sustained damage to the 
       fragile lap ends.  The damage is not severe enough to cause any 
       construction worries, but handling procedures do need to be 
       established and followed.

Full-Scale Prototype Wire Winding

 - The Phase 2 winding paperwork has now been signed by the 12 GeV folks and
   passed on to our contracts people.  The contract should be in place in the
   next 2 weeks.
 - IUCF will need us to make another one or two Moire pattern masks.  Keith has
   provided details on what he would like.  We will have Roger prepare the
   new drawing and take charge of putting together the PR.

Spacer Design

 - Bill has not yet finalized a choice of material.  It looks like the
   best choice may be polypropylene.  He would prefer nylon-6 due to its
   superior mechanical properties, but nylon-6 absorbs water like a 
   sponge.  One problem with polypropylene is that it is very difficult
   to epoxy to it.  If this ring has o-rings on both sides, there is no
   problem here, but Bill needs to be able to attach the gas inlet and
   outlet tubings.  He described a number of potential work arounds.  Bill
   has also inquired about Noryl plastic.  This has been blessed by the
   Hall B folks as fully chamber safe.
 - We will be working to make a mechanical prototype as soon as the
   design is finalized.
 - Bill has completed some studies of gas flow given his gas port design.
   He has tested the ability to move gas through the chamber given a worst
   case hurricane scenario.  He has assumed a pressure change of 300 mb/hr,
   which is the worst ever pressure change seen at JLab.  His design worked
   well under this condition.

Stack Assembly Procedures

 - DSC, Brian, 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.
 - Bill has found some plastic threaded rods that could be used to 
   compress the stack.  We will be receiving some samples shortly and
   will carry out some loading tests.

Cooling System Tests

 - Fernando is in the process of writing up the results from his
   cooling system studies.  Stay tuned for the GlueX note.

Gas System Design

 - Slava is working on a preliminary layout of the gas handling system 
   for the CDC and FDC.  He provided two options for the FDC system design 
   that were essentially a basic version and a fancier version.  Slava's 
   design work was based on the original concept that Brian came up with 
   long ago.  Slava provided some drawings that DSC will review.  We will 
   then continue the design work as we have time.
   

Documentation

 - 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.
 - Kim has provided a draft of a procedures document for the Phase 1 and
   Phase 2 wire frame PCB component attachment. She has merged this
   document with Fernando's cleaning and handling document.  The document
   is being finalized with some additional language on soldering iron
   temperature vs. time profiles.

Small-Scale Prototype

 - Simon and Fernando have completed their studies of the dynamic range
   for the anode and cathode ASIC dynamic range.  The study results are
   posted as GlueX-doc-1070.  Simon and Fernando are now working with the CDC folks
   to help them finish their studies.  No word yet on when they will be
   done and ready for sending things off to Mitch.  Stay tuned.
 - 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.

Engineering Drawings

 - Elke wants signed engineering drawings for the FDC prototype.  These drawings
   will be finalized and signed for each component when we have completed the
   design and moved through the construction phase of the component for the
   full-scale prototype.  Tim has a number system in place and can help oversee
   the completion and review of the drawings as we make progress.

Work List

 - The FDC short-term work list has been posted on the FDC web site).  
   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.