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FDC Weekly Meeting

Date: May 22, 2008

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

Next Meeting: May 29, 2008 @ 1:30 p.m. (tentative)

Cathode Planning

 - Roger and the designers found that the cathode boards in the 3D
   model had all been included mirror reversed from reality.  As the
   3D model was used to define the placement of the daughter boards
   and external connections, a bit of scrambling had to be done to
   make updates to the cathode design.  This took Roger a good chunk
   of time in the past week.  In the future we should label all
   circuit board drawings with labels such as "viewed from the front"
   to avoid confusion and convention issues.
 - We still have not received word, either from Allflex or from the
   other distributor that Roger has found, on the availability of
   the 5 micron Cu/1 mil Kapton board material.  We would like to
   figure this out soon so that it does not hold up the preparation
   and submission of the purchase requisition.
 - Roger has all of the information he needs to now begin preparation
   of the cathode board PR.  We still need to make a final decision
   on how many sets of boards we will order.  This decision will be
   based on how many cathodes we will be making for the full-scale
   prototype (nominally 6 cathodes), but also how many boards are
   needed for cathode R&D and how many are needed for electrical
   and mechanical tests.
 - Fernando pointed out that the new cathode board material will
   not be Kapton, but rather Espanex.  Both materials are polyimides,
   but we need to understand the different mechanical properties
   of the new materials.
 - No progress has been made during the past week on additional solder 
   tests of the rigid-flex assembly to the cathode board mock up.  Roger
   will get the hot air pencil from Fernando and pass it on to Greg
   Arnold's group to complete the next phase of solder tests.
 - 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.  As Roger announced last week, there is
   a new option for the preparation of the ends of the rigid-flex assemblies.
   The company can actually leave the last portion of the assembly without 
   Kapton backing so the copper traces stick out past the end of the flex 
   piece (like little fingers).  This will enable easier soldering.  We 
   will have to investigate this further, but in any case, we will still 
   have to modify the design to allow for proper clearance for the connection 
   between the rigid-flex assembly and the cathode board.
 - Bill looked into ordering a storage box (called a pelican box) for
   the long-term cathode storage (before mounting).  He could not find
   any large enough.  He did find other similar boxes that are plenty
   large enough.  The cost is about $1300.  DSC will talk to Elke about
   this procurement.
 - Brian will modify his Lucite box design for storage of the completed
   cathode planes.  This cathode planes can stack up on top of one another
   (unlike the strung wire frames).  He will make some minor modifications
   to the existing box drawings and prepare the PR.
 - We discussed the holes in the cathodes.  One question is whether
   to have the board house add the holes or try to do this ourselves
   after tensioning.  We all felt that we should have the board house
   add the holes.  Also, we questioned whether there will be a problem
   of having a center hole in the cathodes during the tensioning.  As
   this is our nominal design, we will proceed with this approach until
   we find information that this won't work.

Full-Scale Prototype

 - Kim reported that the HV capacitors for the STBs and HVTBs have
   arrived.  She will find out how quickly Greg's group can solder
   these onto the circuit boards.  If this work can happen quickly
   enough, we will hold up construction of the wire frames for the
   prototype.  Keep in mind that nominally the HV capacitors are soldered
   onto the PCBs during Phase 1 stuffing.  This work is better done
   now before any wire winding is done.
 - Outstanding procurements for the full-scale prototype: 
     * The 2nd construction station PR has not been started.  Brian has
       gotten a quote for a 5 ft by 5 ft granite table of about $4k.  We
       would like to purchase two of these.  One for the clean room and
       one for the frame preparation/assembly area.  DSC will check with
       Elke on this procurement.
     * The rail attachment assembly drawings are now done and they have
       been passed off to FSU for construction.  DSC has posted Bill's
       assembly drawings on the FDC web page.
 - The clean tent in the EEL clean room is now ready for us to move in.  
   Brian will start by moving in a table and a cabinet.
 - Brian needs to provide Casey with a drawing for the modifications to
   the aluminum tooling plate used for our wire plane and cathode
   construction.  Once he does, it will probably be at least 2 weeks before
   we get the plate back.  The cost of a second plate will be on the order
   of $2 to 3k.
 - 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.

Cathode Prototyping

 - Brian has completed a new cathode prototype.  This time the
   cathode was prepared using the tensioning system.  The cathode was
   tensioned until all wrinkles were pulled out.  In performing this
   work, Brian measured that the cathode was stretched roughly uniformly
   in all directions by about 80 mil!.  This version has a surface that
   is drum tight.  
 - Many questions are still floating out there for our cathode design.
     * When the cathode is in its vertical position, what degree of
       bulging is acceptable?  This feeds in to defining what tension
       is necessary to apply.
     * The cathode that Brian prepared was not exactly handled with
       kid gloves.  It was wrinkled to all heck and had defects from
       the manufacturer.  We all suspect that the cathodes from Allflex
       will not have the same defects as the dummy board cathodes from
       CCT.  This coupled with better handling procedures on our part,
       will most certainly mean that less tension is necessary to
       pull out all of the wrinkles.
     * We all felt that we need to develop a tensioning system that is
       full reproducible.  We need to be able to make all cathodes with
       the same applied tension.  Therefore we would like to continue
       to develop the tensioning system to allow it to have this
       capability.  One important piece of information that is not
       known is the tension in the cathode.  Brian will try to setup
       the flatness system laser to measure the tension by blowing
       a puff of air at the surface and then reading back the 
       frequency of oscillation.  To this end, DSC suggested that we
       purchase a role of blank Kapton to act as a cathode dummy that
       will enable us to perform many quick tests without having to
       laminate the 3-piece dummy boards to make the cathodes.  This
       will enable much more rapid turn-around times.
     * We need to have Denny measure the flatness of the new tensioned
     * We discussed modifications of the cathode artwork to include
       strain gauges in the side areas (at least for the prototype
       boards).  This seemed like a pretty neat idea raised by Bill.
       We may be going too far with our cleverness as pointed out by
     * After only about 24 hours, it looks like the Kapton tape on the 
       cathode seams is not keeping the cathode pieces locked in relative 
       to each other (this is the so-called creep test).  The applied 
       tension is obviously very high.
     * If we can apply a fixed tension to the cathodes to fix the
       bulging and remove the wrinkles, and if this leads to a fixed
       and uniform stretching of the cathodes, we can always have the
       board house shrink the boards by a given magnification factor.
 - 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.  DSC was wondering if the 10th
   cathode daughter board (for grounding the cathodes) is still required
   if we are still needing to make other ground connections to the
   cathodes.  DSC will discuss this with Roger and Fernando.
 - 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

 - The Phase 1 wire winding contract ended officially on Friday
   May 2.  DSC has received a preliminary report on the status of
   the work, and this report will be improved by IUCF and updated
   over the next week.  Basically they gave us what they had to
   fulfill the contract requirements, but it is not complete.
 - IUCF provided us with results from the tension measurements of the
   third plane that was wound.  These results indicate that IUCF can
   meet our tension specification of 5%.  Still awaiting final word
   on the tolerances for the wire placement accuracy.
 - 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 has provided measurements for the flatness of one of our
   cathode prototypes backed by 2-mm of Rohacell.  The beer gut has
   been quantified at a 4-mm excursion.  DSC thought that the beer
   gut was likely due to gravitational sag.  Other thought differently.
   Mark suggested that we simply rotate the board by 180 deg and
   remeasure.  This will be passed on to Denny.
 - Denny has now completed modifications of our 1D flatness measuring
   station into a 2D flatness measuring station.  Some programming
   would be required (by some clever young person) to allow for an
   automated measurement system.  This could happen this summer if
   manpower is available.

Cooling System Tests

 - DSC and Denny moved the cooling system test equipment into F117.
   Denny will set it back up in there on Tuesday.  Fernando will take 
   over the measurements and study the cooling properties with a fully 
   loaded preamp daughter board in place.

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.

Gas Volume Definition

 - Bill has put some time into moving the design forward and the
   main points are given earlier in the minutes. Basically as the gas
   fills the volume like a liquid, he wants to include a series of holes
   in the cathode about the full perimeter of the board.  This will
   require modification of the support frame (the G10 skin onto which the
   cathode is mounted) to allow for the gas to go through the G10 and the
   foam core.  Note that any foam exposed to the gas must be sealed.

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.
   Simon will need to account for this gain in determining the required
   dynamic range of the FDC ASICs.    
 - Simon, Fernando, and DSC will prepare a write-up of the analysis
   results and our analysis of the required dynamic range of the
   anodes and cathodes.  Fernando will be in contact with Mitch
   Newcomer on our progress and plans.  Our goal is to have a first
   draft of a report on this work by the end of next week.  After
   the systems review, we will spend a few days to polish up the
   report and circulate it to a wider group for comments before passing
   the information on to Mitch.
 - 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
   will work to find 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.