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FDC Weekly Meeting

Date: August 28, 2008

Participants: Daniel, Simon, Brian, Fernando, Eugene, Bill, Micah, Herun, Jim, Beni

Next Meeting: September 4, 2008 @ 1:30 p.m.

Readiness Review

 - Feedback from the readiness review:
    - The presentations were very well prepared and a valuable exercise.
      Here are the notes that I took during the presentation yesterday.
      At what point are all the drawings going to be signed off?
  - Dan: 
    - Main purpose of large scale prototype
       1. mechanical issues, including physical test of handling, tolerances
       2. signal/noise in electronics (esp. increased lengths of cathodes)
       3. edge effects
       4. beam test/magnetic field study
    - Schedule for wire planes and integration with cathode construction?
      work on impact for construction schedule
  - Bill:
     1. verify that frames remain in their elastic region all during 
        fabrication and assembly. Develop tolerances based on prototype.
     2. major cost is the machining of o-rings 1 day/plane.
     3. eliminate o-ring on one side of cathodes?
     4. tolerances on thickness needs to be reviewed. In particular
        nominal thickness of CH2 is 3/16 = 0.48 cm (instead of 0.5 cm) -
        How is this going to work for the prototype?
     5. Gas flow - check procedures for leaks; calculations for variation 
        of atmospheric pressure (overpressure in chamber); check use of 
     6. size of inner hole
  - Brian:
     1. test cutting center hole in cathode planes
     2. check requirements for size of hole required; possible need to 
        strengthen area around hole
     3. check alignment of ring over cathode board after tensioning
     4. Fernando: develop (backup) cleaning procedures for cathodes;
        soldering tests using samples
  - Bill:
     1. testing layer by layer during assembly?
     2. check gas tightness one layer at a time
     3. precision of pins during assembly to prevent jamming?;
        one precision pin + elliptical?
     4. check alignment procedure, especially relative to stretched cathode
     5. external fiducials - need a third one?
     6. survey prototype?
     7. gas pressure during hurricanes; can the chamber gas get out
        fast enough

Full-Scale Prototype Updates

 - Brian is working to put our clean room/tent together.  He has gathered
   sticky mats, gowns, hats, gloves, shoe covers, cleaning equipment, trash 
   cans, etc..  He has ordered a few things such as sticky rollers to clean 
   the area that will arrive soon.  He will get a bench and a storage closet 
   soon.  Brian is now laying out a procedure for entering into and leaving 
   the clean space that we will all have to follow.  After this procedure is 
   finalized, we will all meet at the clean tent have a walkthrough of 
   everything.  As of now, we will be following full clean room procedures
   in the tent.
 - There have been a series of recent procurements for the FDC that were
   not fully expected.  Please, if you are aware of procurements needed for
   this system, please pass these on to DSC and Elke so that there are as
   few surprises as possible given the current funding situation.  This is
   worth spending a few minutes thinking about.  What will need to be
   bought before now and the end of the year?
 - Roger is still working to finish the design work for the cathode
   rigid-flex assemblies.  He still has several days of design work to do
   and hopes to put the order together in the next several weeks.  We
   will be ordering enough of these assemblies to outfit the entire
   full-scale prototype.
 - Kim has completed the PR for the signal cable connectors and for the
   manufacture of the LV cables.  Elke has already signed the PR.
 - Elke asked us to prepare a spreadsheet listing all expenditures for the
   full-scale prototype.  Kim has started to prepare this including all
   of her procurements (including those through Fernando) and those of
   Bill.  She still needs input from Brian, Roger, Lorelei, Simon, and
   anyone else who has order parts n' pieces.  We will post a draft of
   this spreadsheet in an accessible place shortly.
 - Fernando is considering now how we will make the connections from
   the HVTBs to the power supplies.  He has identified a connector that
   will connect to the baby cables soldered to the HVTB and the cables
   that go to the power supply.  Bill will look into where this connector
   can be placed on the outside of the FDC packages.  If the connectors
   are too large, we can follow up on other options.  More to come.
 - Brian identified a group that can do our SEM wire studies.  Brian will
   bring them our already prepared sample from our earlier SEM tests and
   see if they are content with our slide.  This group also has a super
   high power optical microscope that we can use that might allow us to
   bypass some of the planned SEM studies.  More to come.  Note that
   our new SEM contact can be used to study a sample of the cathode board
   that we received from Allflex.

Cathode Planning

 - Allflex started to work to prepare our boards.  They made one board
   with 2 microns of Cu and immediately had some questions.  They sent
   us the board and we inspected it in the clean tent with all hands on
   deck.  We were reasonably pleased with the quality and appearance of
   the board, but it could have been better.  The entire board seemed to
   have some sort of texture and there were a number of black discolorations
   on the board surface.  The textured pattern mostly pulled out with
   minimal tension.  The black discolorations were some non-conducting
   material, probably solution from the lithography process.  Fernando
   and Simon did a complete QA checkout on the board (resistance and
   capacitance measurements and short checking).  The board met all of
   our specifications.  Good news.
 - After the board inspection, we had a conference call with Allflex and
   relayed to them our findings and what we would like to see improved.
   Allflex indicated that they have some steps that will try to improve
   the board quality.  It is not clear when the board order will arrive.
   However, we did communicate with the some new instructions.  First, no
   hole in the center of the middle cathode board (this was good news for
   Allflex); second, instructions on where to place the side board artwork
   on the Kapton piece.
 - Fernando will arrange to take a sample of the discolored section of the
   board to do an SEM test on it to find out more about what the substance
   is composed of.
 - We have not yet devised methods for handling the boards when they
   arrive from Allflex.  This will have to be developed once the boards
   arrive.  Presently we are planning on doing a battery of QA checks on
   all boards in the first order.
 - Bill has not done any more work on the system to cut the cathode edges.
   More to come when he gets back to this.
 - We have not gotten any further in devising a test to cut the central
   hole out of the cathode boards or deciding when to do the cutting, i.e.
   before or after tensioning.  Elke did a stab test with a thumbtack on
   one of our cathode prototypes and the board did not explode or tear.
   Eugene reported that he had updated some numbers from his tension
   calculations with and without the central hole.  See GlueX-doc-1090 for
   more details on Eugene's work.

Cathode R&D

 - DSC and Chuck have completed work (for now) on preparing the R&D
   schedule for the cathodes.  Copies of the plan have been circulated
   to all folks involved.  Please consult this regularly as you plan your
   work to understand better the order and the time assignments.  Contact
   DSC with questions.
 - Cathode flatness measuring system:
     * It looks like all parts n' pieces have arrived, although Bill was
       not sure about the FSU pieces.
     * The system will employ an old granite table that is now in the
       Physics Storage Building and is ready to be moved to EEL 126.
       This table (4 ft (w) x 6 ft (h) x 1 ft (d)) will be used to support 
       and to define the flatness of the cathode support ring. Bill will 
       ensure that all relevant safety issues are dealt with in the design.
       Mark is doing the work to include the stabilization pieces on the
     * Bill is planning on overseeing the assembly of the system once 
       everything shows up.
     * Micah reported on work that he has been doing to generate contour
       plots of the surface flatness from the 2D data.  He has sent around
       some sample plots for folks to look at, but he still has some work
       to do.
     * We will have to work out a time-sharing plan for the laser measurement
       head for the flatness measurements and the tension measurements.
 - Eugene has posted GlueX-doc-1090 containing all details regarding his
   studies on the cathode tension measurements and the allowed flatness
   variations.  He believes that if we can keep the flatness within 200 
   microns, we will be in good shape.
 - Brian and Bill should begin to layout a detailed outline for the cathode
   construction steps and circulate for feedback.

Machine Shop Work

 - The modification to our aluminum assembly jig is complete and it is
   now sitting in EEL 126.  The new aluminum assembly jig is also
   complete and is now in the EEL clean room.  Brian has test fitted the 
   STBs and HVTBs onto the jig plates and has reported that everything 
   fits properly and the clearances are adequate for all components.

Wire Frame Construction

 - The frame that was used for our wire tension load test (which is 
   discussed in the FDC TDR) will be modified to include the pockets for the 
   rigid-flex assembly and the bolt holes.  It will be machined to the 
   nominal I.D. and O.D. of our wire frames.  The foam core and the G10 
   skin will be removed to an I.D. of 1032 mm to account for the problem 
   with the HV decoupling capacitor placement.  The frame should be done
   in the shop before the end of next week.  The plan is to redo our loading
   tests and measure the in-plane and out-of-plane distortions of the
   wire frame up to a load of roughly 50 lbs (the full wire load is about
   35 lbs).  We still have some details to work out on the test plan
   specifics.  Bill will talk to Tim about completing a series of FEA
 - The nominal wire frame construction plan devised by Brian will be
   our starting point for construction.  Folks should look this plan over 
   in some detail and we will step through it before the start of 
   construction to make sure that no steps are left out.  The plan is posted
   on the FDC web page under the procedures link.
 - 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.
 - Simon and Herun have completed the HV checkout of the STBs. Some details 
   are included in the FDC logbook entry #377. Two suspect capacitors were 
   found and replaced.
 - The HVTB electrical checkout has also been completed.  As there are no
   capacitors on these boards, the 1M resistors were checked as O.K..  No
   problems were found.  As reported in the last meeting, there were some
   filter capacitors soldered to the face of the HVTBs that should not
   have been put on until the phase 2 stuffing.  These were removed and
   the boards cleaned before the HVTB checkout began.
 - 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.
 - DSC has prepared two documents for our wires.  One for the specifications 
   for the sense and field.  A second focusses on what tests we will do
   with the wires.  These documents have been prepared based on the CLAS
   specifications and have been updated after recent discussions with
   Steve Christo.  Brian will send these to CFW and Little Falls with our
   procurements for the full-scale prototype.  When these documents are
   finalized, they will be posted to the FDC web page.
 - DSC and Fernando met with Kim about redoing the capacitor placement on
   the STBs.  All capacitors must be moved radially inward of 1020 mm
   diameter to allow sufficient room for the wire frame o-ring on the
   G10 skin.  It looks like there is sufficient room to do this.  Kim
   and Fernando will meet one more time before Kim fully embarks on this
 - We talked about appropriate containers for storing the wire frame
   PCBs.  We will revisit this issue before the final detector procurement.
   For now, Fernando has purchased some containers from Target that will
   do the job.  It might be that we ultimately want to supply the PCB
   company with shipping containers as even inserting the boards into
   static bags can cause unexpected damage.

Test Frame Wire Winding

 - IUCF has supplied the official report from the Phase 1 wire winding
   continuation.  As Elke and I have some questions with the document, we
   will have a phone conference with them next week.
 - We are awaiting an official budget for Phase 2 and we will also review
   this in our conference with IUCF.  If the budget comes out too high,
   we will begin more serious dicussions with IUCF on bring their wire
   winding facility to JLab.

Spacer Design

 - Since our last meeting we have done more thinking about the design
   of our spacer ring.  It was to be composed of a composite design
   with an o-ring groove on each side and a gas port through the middle.
   We decided at our last meeting that the design would be greatly
   simplified if we could replace the composite with a solid material
   and we began focussing on CH2.  In the mean time, we have come to
   the realization that there are better materials (from a structural
   standpoint) than CH2, e.g. nylon-6.  Bill is looking into this and
   will let us know what he finds.  We do need to ensure that what
   we use has a density close to that of CH2 (or the composite) and is
   chamber friendly.
 - We are also strongly considering epoxying the spacer ring directly
   to the face of the cathode.  There seem to be no compromises here.
   We eliminate an o-ring and give Bill more room for his gas feedthroughs.
 - We will be working to make a mechanical prototype as soon as the
   design is finalized.

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.
 - Bill has found some plastic threaded rods that could be use 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.


 - 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 needs to merge this
   document with Fernando's cleaning and handling document.

Small-Scale Prototype

 - Simon and Fernando are in the home stretch on completing the specification
   of the cathode and anode ASIC dynamic range.  All required measurements
   have been completed and work is ongoing to finalize the test results in 
   the document.  What we have so far is posted as GlueX-doc-1070.
 - 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.

CAD Model

 - We discussed a bit about making sure all relevant design features
   of the FDC are in the full CAD model.  Tim will have Slava work to
   put in the capacitors and resistors on the wire frame PCBs into the 

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.