Minutes 2-21-2008

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FDC Weekly Meeting

Date: Feb. 21, 2008

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

Next Meeting: February 28, 2008 @ 1:30 p.m.

Test Frame and Prototype Wire Winding

 - IUCF has just responded to JLab and they have provided a budget for
   the Phase 1 and 2 wire winding.  It sounds like things are moving
   along and word will be sent around once we have a signed contract.

Full-Scale Prototype

 - Elke has now given us a budget for construction of the full-scale
   prototype.  The total amount is $150,000.  This number is consistent
   with the budget estimate that DSC provided to Elke for construction
   of half of a full FDC package (U/V/W layers).
 - The procurement effort for the full-scale prototype is now proceeding
   in earnest.  Kim has prepared a PR for the wire frame components and
   connectors that Elke has already signed.  The PR for the wire frame
   circuit boards is now out for quotation and we expect a response by
   tomorrow.  We will plan on order 5 full sets of circuit boards.  Elke
   is ready to sign the PR as soon as our quote comes in.
 - DSC needs to provide Kim a handling and transport requirement document
   for the wire circuit board order.
 - Brian will prepare several PRs for the frame construction. This will
   include the G10 rings for the cathodes, wire frames, and spacers, the
   Rohacell foam for the cathode frames (4 mm thick), the spacers and
   wire frames (3.4 mm thick), and or the cathode backing (2 mm thick).
 - Brian will also prepare a PR for the construction of a second assembly
   station.  This includes a second granite table and aluminum jig plate.
   This second station is essential to enable us to complete the construction
   of the prototype by June.
 - We are working with Roger to complete the design and layout of the
   cathode boards in the next 2 weeks (or less) so that procurement of
   the boards with 2 micron thickness can commence.

Grounding Issues

 - The grounding scheme of the wire frame circuit boards has been
   settled.  We have been sure to design the grounds so that the wire
   frame circuit boards do not present a current loop for protection from
   eddy current forces in case the solenoid quenches.  The ground will
   be defined from an external source and single small spade connector
   will be soldered to each board.
 - The connection of the ground to the aluminized mylar ground plane is
   defined in principle, but the plan must be prototyped.  Currently we
   will use the same spade connectors as for the wire frame ground. 
   Several of these space will be included on the back of the cathode
   board G10 support skin using an epoxy connection.  The two sides of
   the aluminized mylar gas window will employ conducting epoxy to
   make the ground connection.
 - The grounding scheme for the cathode was also discussed.  The
   situation is a bit more tricky mechanically and we are looking to
   distribute the external ground to the cathode board ground pours
   through the cathode daughter board and rigid flex cables (being sure
   to keep this ground separated from the preamplifier daughter board
   ground).  Roger will work with Fernando to finalize the specification.
 - For safety reasons we have decided to replace the 6.3 micron thick
   aluminized mylar ground plane with a 12.7 micron thick aluminized mylar
   ground plane.  This was done to minimize the possibility of the
   ground plane (which is also a gas barrier between neighboring layers)
   of blowing in the case of overpressure.

Composite Cathode Discussion

 - Brian has completed the construction of a composite cathode board.
   This board employed a butt joint between neighboring dummy cathode
   boards and a 2-mm thick low-density Rohacell backing.  The foam core
   in the support ring was 5-mm thick (instead of the nominal 4-mm).
   Simon will put a photograph in the logbook.  A couple of observations
   about this board.  One is that this composite cathode has no degree
   of sagging or bulging when in the vertical position.  Also the butt
   joint approach that Brian employed looks absolutely beautiful.  The
   three piece circuit board really looks like a single board.  Finally
   there were some noticeable wrinkles in the Kapton on the G10 skin in
   several places.  Brian will look into this to remove this problem as
   he makes the second cathode board to complete the cathode sandwich.
 - The cathode is quite floppy and DSC is worried about vibrations from
   sources in the hall being transmitted to the cathodes.  Tim has
   indicated that the only way that this could happen is if the
   resonant frequency matched the driving frequency.  However, we still
   want some assurances that vibrations will not be an issue in our
   current design.  Tim will do some calculations and Brian will follow
   up with him.  Tim has also indicated that he has a list of all of
   the broadcast frequencies in the hall (pumps, etc.).  We need to
   compute the natural frequency of our cathode design and then develop
   a simple mechanical test.
 - Brian will work on several things as he constructs the second
   cathode for the sandwich.  One is to include a support ring for
   stiffness that goes between the 2 mm thick foam cathode backing and
   the ground plane.  This is not part of the nominal design, but will
   be studies.  Also he will attempt to seal the exposed Rohacell on
   the cathode backing with a thin layer of Kapton.  This is something
   that we believe to keep the contaminants in the chamber volume

Cathode Board Issues

 - Roger has agreed to take on the following responsibilities:
  • Contact flex board material supplier and flex board manufacturer to converge on the following issues:
  - flatness specifications
  - elimination of cathode surface defects
  - handling procedures and requirements
  - transport requirements for boards
  - pre-made holes in cathode boards
  - QA plans and board checkout requirements at board house
  - minimum copper thickness (we would love to get our hands on
     boards with 0.5 micron and 1 micron copper for testing)
  • Develop QA and board checkout document for the cathode flex boards upon delivery.
  • Take care of all cathode flex board QA and board checkout for certification before cathode construction.
  • Develop QA and board checkout document for the cathode daughter boards upon delivery.
  • Take care of all cathode daughter board QA and board checkout for certification before installation in prototype.
  • Arrange for cathode daughter board stuffing at JLab (talk to Kim as she is arranging this for the wire plane circuit boards). Develop stuffing and cleaning procedures document (consult with Fernando who is preparing a similar document for the wire plane circuit boards).
  • Finalize cathode ground pour definitions and design to avoid anycathode current loops for protection from eddy currents induced with solenoid magnet quench.
  • Finalize plans for connecting external ground to cathode boards (consult with Fernando who is developing a plan for the wire plane and ground plane connections).
  • Take the lead in the procurement of the cathode boards and the cathode daughter boards
  • Act as the contact for the cathode daughter board stuffing.

Gas Volume Definition

 - Bill has completed a parasolid model that he will give to Dave Meekins
   to complete the flow/pressure calculations.  We need to decide soon
   what the holes in the cathodes need to be.  We are already planning
   for the inclusion of a beam hole in the cathode.  However, there is
   also space available between the last cathode strip on either side of
   the board and the edge of the G10 support skim.  Do we need to have
   these opened up?
 - Bill has worked with a local company to do some test laser cutting
   through a cathode board sample.  After adjustment of the laser power,
   clean and precise cuts were possible.  Roger will interact with the
   cathode board manufacturer to see what they can do.  If this also a
   laser cutting procedure, we can just have them do the work to reduce
   handling of these fragile boards.


 - DSC, Fernando, Kim, and Roger will be meeting with Greg Arnold from
   the accelerator to discuss the needs and plans for stuffing of the
   wire frame circuit boards.  Greg's group is available for this work.
   This meeting will be on Monday next week and we will also get a chance
   to look at their facilities.

Cooling System Update

 - Bill has devised a test set up for study/testing of the preamplifier
   board cooling system.  Denny is putting this together in his spare
   time.  He has been working in Hall B and will be back with us next

Small-Scale Prototype

 - Brian has been delayed in assembling the +/- 75 deg cathode boards.
   He has the boards and support frames in hand, and will get to this
   mounting shortly.

FDC Mini-Review

 - The committee report from the mini-review has not yet been delivered.
   As soon as it appears, it will be circulated to everyone for review.

Cathode Daughter Boards

 - Roger has nearly finalized the cathode daughter board design and he
   has now included the ERNI connectors.  We still need to finalize how
   to get the external ground to the boards.  Roger is also working with
   Chuck to ensure that there are no clearance/positioning issues with
   his cathode daughter board design.

Cathode Flatness Measurements

 - Bill has been in contact with the machine shop.  In addition to the
   horizontal mill machine, they also have a coordinate measurement
   machine that might be more appropriate for our needs.  We discussed
   the problems with the laser measurement system that Bill found and
   have to overcome the hurdle of how to read this out or how to
   coordinate the CMM output with the laser position.  Brian will
   explore getting a software person from his side.  Perhaps also Elliot
   could be of assistance here.  Bill will continue to gather information
   so that we can converge on a solution.

Meeting on LV/HV System Design

 - The next meeting with Joe, Fernando, and DSC on the layout and
   design of the LV and HV systems for the tracking chambers will take
   place on Monday.  We are working with Joe to finalize the system
   design.  Over the last two weeks we have made the decision to
   reduce the number of LV cables in the system by a factor of two.
   The ERNI connectors were ultimately felt by Fernando to have too
   much redundancy.  This redundancy can be reduced to feed more 
   preamplifier cards with a single power line.

FDC Insertion Planning

 - We discussed in general terms the issues with the installation of
   the FDC from the upstream end.  We need someone to concentrate on
   all of the associated issues with this plan.  What is the clearance
   needed for the FDC cables outside of the CDC?  How will the cables
   be managed and strung so that the FDC can be inserted and extracted
   without touching the cables (and without destroying the detector)?
   What will the shell about the CDC look like?  Joe Beaufait's name
   came up as a natural for this work.  We need to find out if he is
   available to take on this work in a serious manner.

Upcoming Reviews

  - The combined tracking/PID review for Hall D is scheduled to take
    place on March 27 and 28.  At this point, we are converging on
    a charge and the list of speakers.  We have to prepare talks and
    backup materials for the FDC, CDC, and charged particle PID systems.
    The details will be worked out over the next week or so and
    preparations will continue from now until the review.
  - In preparation for the meeting, we will need an updated set of
    design drawings for the FDC web site.  New drawings from the
    mechanical model will need to be provided that reflect the current


 - 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 lastest 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.