Minutes-4-3-2008

FDC Weekly Meeting

Date: April 3, 2008

Participants: Daniel, Simon, Kim, Fernando, Elke, Roger, Mark, Jim

Next Meeting: April 10, 2008 @ 1:30 p.m.

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Cathode Planning

 - The nominal design of the FDC cathodes is 2 microns of copper on
   1 mil of Kapton with a 2 mm Rohacell backing.  In the current design, 
   the ratio of materials copper/Kapton/Rohacell/epoxy is 32/20/36/12.
   Thus copper is not the dominant contributor.  We are also worried
   about going to much thinner copper for two important reasons, namely
   the thinner the copper, the harder it is to solder to, and also, the
   thinner the copper, the more delicate the boards are and the more
   susceptible to damage they are.  Thus we are going to attempt to
   stay close to our nominal design as we seek out a board supplier
   and a board house.
 - There are two technologies for manufacturing our cathode board
   material.  The first is vacuum deposition.  This process necessarily
   focussed on very thin copper layers (below a tenth of a micron say).
   It may not be possible to use this technique to prepare boards with
   2 micron of copper, but it is worth investigating.  The point is
   that 2 microns of copper from this approach is pushing the technology
   from above.  The second approach for board manufacture is flashing on 
   a thin layer of nickel and then a copper layer.  This approach is more
   suitable for thicker layers (say above 5 microns).  This our 2 micron
   copper thickness desire is pushing the technology from below.
 - The biggest issues in finding a material supplier are both the
   copper thickness AND the physical size of our boards.  Of course,
   we would like to have our cathodes made from a single flex board, but
   even with our 3 piece design, we are really pushing what companies
   can provide. 
 - We have learned recently from our Sheldahl sales representative, they
   they are not able to prepare our nominal cathode materials for the
   time being as they are reorganizing their production lines.  Roger
   will be the sole contact with them.  He will communicate with both
   the Sheldahl sales representative as well as the technical folks.
   The question is, when will they be able to supply something close
   to our board material?  We would be willing to purchase the full
   amount of this material, for both the full-scale prototype, as well
   as the production cathodes.
 - Jim raised the idea of purchasing flex boards with thicker copper
   layers and then plasma etching them down to our requirement.  He
   said that this approach has been used before.  Jim will make a
   list of contacts and provide them to us.  Kim will take responsibility
   for being the contact point on this front.
 - Even though vacuum deposition is usually used to prepare flex boards
   will very thin copper, we should not rule out invesigating whether
   we can use this approach for our nominal boards.
 - Jim will talk to his contacts in Germany to prepare us a list of
   sales representatives and company contacts so that we can start to
   make some in roads toward finding both a material supplier and a
   board house.  Kim will be the contact point for dealing with the
   companies that are provided.
 - DSC will prepare a specification document for the cathodes, including
   tolerances, and supply this to Kim and Jim.  After we find one
   or (hopefully) more companies that might be able to provide what
   we need, we will then start discussion of our handling requirements
   with them.  DSC has already prepared a document for the handling
   requirements.

Full-Scale Prototype

 - The Rohacell order arrived on Tuesday of this week.  As Brian was
   away today, we do not know the status or expected delivery date of
   the G10 order.  DSC will work with Brian to prepare a construction
   time line for the wire frames so that they are ready to go to IUCF
   for the Phase 2 shortly after the completion of the Phase 1 winding.
 - The 50-pin connectors have all arrived (for both the chamber end
   and the electronics end).
 - All wire frames PCBs have arrived and passed our QA checks.  All
   sets that were to be stuffed by Greg Arnold's group have been
   completed (Phase 1 stuffing only).  Kim has delivered the completed
   boards to Simon for storage.
 - Kim has received the ERNI connectors.  The HV capacitors are expected
   to arrive by the end of May.
 - The order for the cathode rigid flex boards has gone out and should
   be delivered early next week.  The cathode ground boards will arrive
   in about 2 weeks.
 - No progress has occurred on modifying the aluminum construction jig
   as Brian has not yet gotten to this.  Hopefully we can converge
   on completing this work before Brian goes to IUCF. 
 - DSC and Brian talked to Jack Segal about occupancy of the clean
   tent in the EEL building.  We are expecting to have occupancy at
   some point in the first part of this month.  More details to come.
   Brian needs to order the second construction station for the
   full-scale prototype construction.

Test Frame Wire Winding

 - DSC has been in daily contact with IUCF as they prepare to begin
   the wire winding procedure for Phase 1.  They believe that the
   wire winding system is essentially ready and they are working on
   preparing the wire placement measurement system and the tension
   measurement system.  They have laid out the design for a support
   frame and will have this made at the IUCF shop as they can get
   it done before we could and they need this before Brian can go
   out there.
 - We have shipped IUCF two of our wire frames and the aluminum
   strongback.  Hopefully this will arrive in Bloomington on Tuesday
   or Wednesday of next week.
 - They are hoping to be ready for Brian now on the week of April 13,
   but they believe that this may already be too tight, and that the
   week of April 20 is more likely.  They will give us feedback as
   soon as they know.
 - 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.

Composite Cathode Updates

 - No progress on completing the composite cathode cathode sandwich
   as Brian has been away most of the week.  This prototype will be 
   worked on to finalize the Rohacell sealing procedure, the ground plane 
   attachment procedure (including connections to the outside), and 
   attachment of the gas ports.

Grounding Issues

 - Fernando will supply an overall grounding specification document 
   very soon.  He is working on it.

Gas Volume Definition

 - Bill has been in contact with Dave Meekins as he continues to work
   on studies of our gas volume definition.  Dave has recently got one
   of Bill's models to work.  While the results are considered very
   preliminary, what seems to be coming out is that there are problems
   with the gas delivery with the model with only the central hole.
   There are clearly dead regions (or low flow regions) in the space
   between the ground plane and the cathodes.  Clearly our design is
   not final and we will have to take the output from the these
   calculations, and perhaps from a real-world study of a prototype,
   to converge on a final design that will meet our requirements.

STB/HVTB Discussion

 - Based on the work that Greg Arnold did, he will work with Kim
   to update the cleaning/assembly procedures document that Fernando
   initially came up with.  Fernando's document will be modified
   to reflect what Greg's group actually could do.  Fernando will
   review the marked up document and provide feedback on what we
   will ultimately be satisfied with.  The question is what we can
   accept if the wire frame circuit boards are stuffed in house.
   If they are stuffed by an outside company, we will be able to
   ensure industry standards for handling and cleaning.

Cathode Board Discussion

 - Roger has ordered a sample test setup that includes a G10 frame
   with a piece of a cathode board mockup for continued solder tests.
   His tests of soldering to a dummy cathode boards (covered completely
   with Copper) were not successful.  There was too much of a heat
   sink.  His approach was to use a small-tipped soldering iron.
   He did report that even at 800 deg on the iron, there was no trouble
   with the copper pealing off the Kapton backing.  If the soldering
   approach does not work, Roger will move to a hot-air reflow technique.
   Given the new test fixture that he has ordered, he believes that he
   should be able to finalize the rigid flex board attachment.  He
   will prepare a procedures document based on the final approach that
   he comes up with.
 - 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.
 - Roger was planning to do some test soldering for the rigid flex
   cables to a sample cathode board.  No update was given during the
   meeting.

Small-Scale Prototype

 - During the past week, Simon's DAQ computer bit the dust (goodbye
   computer, we hardly knew ye).  He has gotten another replacement
   and is getting everything working again.  He mananged to collect
   about 3 days worth of data with the new 2 micron cathodes.  As
   reported last week, it basically worked.  However there are some
   problems in the calibrations that Simon has to figure out.
 - Simon's plan is to complete the studies with the current configuration
   (Hall B SIPs, charge-integrating ADCs, 90-10 mixture).  He will
   then study the setup with the 40-60 mixture before putting the
   ASICS/FADCs back into the system.  He will then move on to perform
   quantitative studies of the FDC dynamic range.

ASIC Studies

 - We had a meeting earlier in the week on the measurement requirements
   with the CDC and FDC systems for the ASICs.  We want to be able
   to get all required information to Mitch Newcomer so that he
   can make any and all design modifications for the ASICS to be able
   to meet the June submission deadline.  Fernando is working to prepare
   a full test plan document that he will circulate early next week for
   feedback from the group.

Cathode Flatness Measurements

 - The laser measurement system from Acquity Laser has arrived.  What
   we got for a 30-day trial is a laser, a laser sensor, and a power
   supply box.  There was also some documentation.  
 - DSC would like to meet in the shop with the equipment, and with
   Brian and Bill to go over the plan for setting this system up.
   DSC is concerned with the current cathode construction procedure
   and the looseness of the cathode surface.  When the plane is
   vertical, there is a noticeable concavity in the surface this is
   not acceptable.  The question is whether the 2 mm backing is
   actually helping or doing what it should.  Do we need to consider
   additional tensioning of the cathode boards before attachment to
   the frames, etc.  The measurements of one of our cathode prototypes
   in the vertical position will help us to quantatively understand
   the scale of the gravitational sag of the boards.

Tracking System Design Reviews

 - The final design review for the tracking chambers and particle
   identification system took place at JLab on March 27.  This
   system reviewed the FDC and CDC systems, as well as timing in
   the BCAL and TOF systems.  By all measures the review was a
   complete success, with no issues or major recommendations brought
   up during the review close out.  The FDC design was essentially
   blessed and was not even mentioned during the close out period
   from the standpoint of issues at any level.
 - DSC wants to thank everyone who contributed to making this a
   successful review.  Your time, energy, patience, and skills are
   fully appreciated.

Miscellaneous

 - DSC is working to schedule combined CDC/FDC meetings, probably
   on Monday afternoons.  This meeting will focus on combined mechanical
   and design issues for the two systems.
 - DSC is reviewing the FDC construction budget to give Elke any
   substantial changes (either down (yeh, really likely) or up).  This
   work will be completed early next week after we get updates on
   the cathode rigid flex boards and the wire frame circuit boards.

Drawings

 - 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.