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FDC Weekly Meeting

Date: May 29, 2008

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

Next Meeting: June 5, 2008 @ 1:30 p.m.

Cathode Planning

 - Allflex has identified a distributor for the 5 micron Cu boards.
   Roger is beginning preparation of the cathode board PR.  He still has
   some work to complete with laying out the gas holes defined by Bill.  In 
   doing this hole layout, he is making some minor modifications to the trace 
   routing to improve clearances.  Presently there are 24 gas holes located
   between the through holes.
 - Chuck has to include the gas holes in the G10 skin onto which the
   cathodes are mounted.  He will begin this work over the next week.
 - Before the cathode board PR is submitted to Allflex, Fernando will be
   responsible for "blessing" the board layout (electrical issues) and
   Bill will be responsible for "blessing" the gas hole layout.
 - Our present design for the cathode includes a single grounding point
   through the 10th cathode daughter board.  Recently Fernando has indicated 
   that he is worried that a single connection might not be optimal and
   that we might want to add more connections about the perimeter of the
   cathode to keep all ground paths as short as possible. We are working
   to include a way to add ground connection points, possibly through
   copper tabs mounted in cut-outs beneath the cathode board.  In this
   regard DSC questioned whether the 10th cathode daughter board was
   required.  Fernando convinced us that for the prototype, we want to
   leave the 10th cathode daughter board in place as it may ultimately
   prove to be sufficient and he wants the flexibility to check this out.
 - Allflex indicated that they will not be able to provide a precision edge
   on the delivered boards.  We decided then that we will request all boards
   be delivered in 19.5-in wide sheets (i.e. the full width of the board
   material possible from the material supplier) and we will trim the excess 
   here.  Obviously we must now come up with a process to cut the boards to 
   provide a precision edge.  This is highly desireable as our present
   construction technique butts the individual cathode board pieces up
   against each other.  We then rely on this butt joint and the included
   sighting fiducials to ensure proper board-to-board alignment.  If we
   do not have a precision edge and a butt joint, it makes the cathode
   construction procedure more complicated.  Bill will look into procuring
   appropriate precision Starrett steel tooling for cutting the boards.
 - The board house will not pre-cut the holes for the through bolts or the
   gas holes.  These holes will be added by us after the cathode boards
   are assembled and the frames included.  We still have to finalize the
   tooling for this.  Bill and Brian will work together to make a decision.
   We will have Allflex cut the center hole (for the prototype, we will 
   request roughly an 8-mm diameter hole.  For now, we will specify only 
   a loose tolerance of 0.5 mm on this hole.  This was felt to be good 
   enough for the prototype boards.
 - We discussed how many sets of boards we should order.  This depends on
   if there will be any potential problems with the boards upon arrival
   that would cause us to reject them, what we can expect in terms of
   problems in assembly that would lead to waste, how many boards we must
   set aside for testing (electrical and mechanical tests will be needed),
   and what the available budget for the cathode order is.  Our initial 
   guess is that we would require a minimum of 4 sets of boards of each 
   type (2 micron Cu and 5 micron Cu).  We will continue to ponder on this 
   over the next week.  DSC contacted Elke after the meeting to get her 
   input on the available budget for this order.
 - Roger believes that the cathode board PR should be on Elke's desk by
   the end of next week.
 - Note from last week: The new cathode board material will be Espanex 
   and not be Kapton.  Both materials are polyimides, but we need to 
   understand the different mechanical and electrical properties of the 
   new materials.
 - Additional solder tests of the rigid-flex assembly to the cathode board 
   mock up will proceed after Roger gets the hot air pencil from Fernando.
   This work will wait until the cathode board PR is completed.
 - 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 will look into this and will make
   a report at our next meeting.
 - Bill completed the procurement requisition for the cathode board
   shipping/storage container and it was signed by Elke.  We need to make
   a final decision on if the box should be shipped here or directly to
 - 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).  He will make some minor modifications
   to the existing box drawings and prepare the PR.

Full-Scale Prototype

 - Before the construction of the wire frames begins, we decided to have 
   Greg Arnold's group solder on the HV capacitors (that just arrived) to 
   the STBs and HVTBs.  This work is in progress and will be completed by 
   early next week.
 - The PR for the 5 ft x 5 ft granite table has been completed and submitted
   to Elke for signature.  Note for now that we decided to order only one
   table although we will eventually need two of these tables.
 - Brian is working with Kim to complete the drawings for the aluminum jig
   plate to allow for clearance of the resistors and capacitors.  This work
   is nearly done and then immediately submitted to Casey.  Once this is 
   submitted to the machine shop, they will modify the existing tooling 
   plate and make a second plate for our second construction station.  We 
   discussed the need to update our frame construction process to allow this 
   jig plate to have some guides to align it in proper position to ensure 
   that it does not damage our frames or our circuit boards when it is lowered
   in place.  Brian will begin to ponder this and believes that this is a
   solvable issue.
 - Brian has moved a storage cabinet into the clean tent in the EEL clean room.
   He will also shortly move in a work table.  The granite table should be
   delivered in 2 to 3 weeks.  The question is whether we want to put this
   table in the clean room tent or in EEL 126.  We will figure this out
 - 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.
 - Until the aluminum jig plate is ready and the granite table is delivered,
   Brian can still begin the wire frame construction process.  We have hope
   that the frame construction will actually begin before the next FDC

Cathode Prototyping

 - The first tensioned cathode was completed last week and it was noticed
   that it was pulling apart slightly at the seams between the cathode
   board pieces.  As of today, no further changes have taken place and the
   board seems stable.  Certainly the seam problems and the stretching
   of the Kapton that was noted indicated that the applied tension was too
   high.  Brian will be working to purchase bare Kapton and then to develop
   a tensioning system that will allow for repeatable assembly parameters.
   Ultimately we would like the cathode construction procedure to be based
   on dialing in a specific tension into the cathode board during the
   frame mounting process.  Brian will begin by ordering a roll of 48-in 
   wide Kapton for this.  The ultimate tension that we 
   choose for the cathodes will be based on the allowable sagging (aka beer 
   gut) on the cathode, the allowable distortion or stretching, and the 
   stress on the seams.  More to come on this as we make progress.
 - We will try to develop a cathode tension measuring system using our laser 
   measurement head.  The procedure will be to direct a puff of air at the
   center of the cathode and measure the amplitude fluctuation vs. time
   through the laser measurement system.  Fitting this amplitude distribution
   will give us (hopefully) the fundamental frequency that we should be
   able to convert into the membrane tension.  
 - We discussed again the need for providing additional ground connections
   to the cathode board.  Brian indicated that he will be studying possible
   ideas when he makes connections to the ground plane that he will be
   attaching to the cathode prototype.  This idea could be developed
   for the cathode ground attachment.
 - Our 12-GeV safety watchperson, Cindy Saban, has been documenting
   the cathode construction procedure and can provide a first draft
   of a procedures document.  Bill and Brian can flesh this out and
   help to finalize the write up.

Test Frame Wire Winding

 - IUCF provided a report of the results of the Phase 1 wire winding.
   Several of us are going over this report to generate a list of
   talking point for a phone conference with IUCF next week.  Hopefully
   as a result of this phone meeting, IUCF will move to prepare a
   budget and schedule for the Phase 2 wire winding.  DSC has prepared
   a discussion list for this meeting and circulated it to the relevant
   folks.  He will pass on this list to IUCF.  They indicated that they
   will continue to work on performing additional measurements on the
   two wire planes that they have to continue to try to resolve remaining
   issues with their wire winding system to ensure that they can meet
   our position and tension specifications.
 - 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

 - Denny is continuing to study the flatness of our prototype cathodes.
   He is scanning the first Rohacell-backed prototype performing
   measurements at different angles to understand how the bulging depends
   on rotation angle.  He has also gotten our second Rohacell-backed
   prototype and is now performing measurements.  We would like to see
   how reproducible the cathode bulging is from cathode to cathode with
   our current construction process.  Shortly Denny will get the tensioned 
   cathode and perform some scans on its flatness.  Results coming shortly.
 - We are planning on continued upgrades of the flatness measuring
   system to enable this to perform automated 2-D scans of the completed
   cathodes.  Denny will be gathering some additional parts and pieces,
   including limit switches, etc. to start this upgrade.  The summer
   student that Dave Lawrence had found to take this project over fell
   through, so he rounded up a master's student from CNU (Micah).  This
   student will work to take the system over from Denny before he
   disappears on June 8 (Denny, not the student).

Cooling System Tests

 - Denny reassembled the preamplifier cooling system in F117 and set
   the flow and temperature.  After letting the system come to
   equilibrium, Fernando took over the system for the cooling tests
   of the preamplifier daughter boards.  He will install temperature
   readout on the upstream and downstream sides of the coolant line
   feeding the preamplifier card.  Results of these studies coming soon.

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

 - Work continues on characterizing the preamp daughter boards to
   specify the ASIC dynamic range for both the FDC cathodes and
   wires.  Simon is extracting from the data the amplitude distributions.
   He is making progress in acquiring spectra where noise-related
   events are not included (so that we do not bias our results).  Once
   he has acquired the spectra for minimum ionizing particles, we need
   to convert this into the numbers required for the more heavily
   ionizing particles of interest.
 - Fernando has characterized the gain of the preamp/shaper/cable in
   Simon will need to account for this gain in determining the 
   dynamic range of the FDC anode and cathode ASICs.    
 - Simon, Fernando, and DSC will prepare a write-up of the analysis
   results and assumptions that went into specifying the dynamic range
   numbers for the anodes and cathodes.
 - Brian will perform an optical scan of the cathode strip edges in one
   of our spare 2 micron Cu cathode planes.  We want to make sure that
   there are no obvious systematic problems with the construction.  He
   has found a x50 microscope to do this work.


 - 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.