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FDC Weekly Meeting

Date: July 31, 2008

Participants: Daniel, Simon, Chuck, Beni, Brian, Fernando, Eugene, Bill, Micah, Kim, Herun, Mark, Dave

Next Meeting: August 7, 2008 @ 1:30 p.m.

Cathode Planning

 - Cathode delivery date is expected within roughly 1 week.  Roger
   indicated that he sent the shipping instructions Roger for the now
   longer cathode boards to Allflex.  Kim will contact JLab shipping 
   and receiving to be alerted as to when the cathode shipment arrives.
   They will be instructed not to open the shipping box to reduce 
   contamination possibilities of the boards.
 - Fernando has posted GlueX-doc-1082 detailing the electrical QA test
   plan for the cathode boards.  This test plan will take place in the
   clean tent immediately on receipt of the boards from Allflex.  Once we 
   characterize and perform QA on the boards, we want to communicate this 
   information to Allflex and if everything is acceptable to us, move to 
   complete the order for the remainder of the cathode boards for the 
 - Fernando and Brian should gather together all of the necessary parts
   and equipment for the cathode QA checks so that everything is ready
   to go when the boards arrive.  Roger provided a list of the length
   of each of the cathode strips.
 - The cathode boards should NOT be removed from the shipping container
   without developing an internal plan for moving and handling.  The
   cathode shipping box should only be opened in the clean room.  We
   will install the gas connectors and flow nitrogen through this box
   shortly after its arrival to reduce contamination and oxidation.
 - The new granite table has arrived and is now sitting in the high bay
   of the EEL building in two pieces.  Brian will have this moved into
   the clean room tomorrow and put into place.  The other group that
   was using the clean room has moved out and it is vacant again.
 - Bill has done some thinking on a technique to cut the edges of the
   cathode boards.  He will put together a sketch of his design and
   circulate it when it is ready (within a few weeks).  Once we hash things
   out a bit and converge on the design, we will then begin procurement of 
   the necessary parts.
 - Roger plans on ordering a set of 3 to 5 of the new cathode rigid flex
   assemblies with the copper fingers.  This procurement should take place
   before the end of August (funds permitting).
 - 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).  As this box is not needed for
   at least several months, this work is not super high priority.
 - Brian and Bill should begin to layout a detailed outline for the cathode
   construction steps and circulate for feedback.
 - We discussed approaches to cut the gas holes and the beam hole in
   the cathodes.  DSC is not big on sending out the cathodes to an
   external company for laser cutting because of issues of board handling
   and shop cleanliness.  We discussed an alternative of developing a
   crush cutting system and Bill will begin a design of such a system
   shortly.  It is not clear at this point whether we want to cut the
   cathodes before they are assembled (i.e. on the 20-in wide boards) or 
   after they are tensioned.  There are pros and cons on both sides of the 
   ledger.  We will have to certainly do some R&D work to finalize what we 
   will do.

Machine Shop Work

 - After internal discussions on how to deal with scheduling the FDC
   work in the JLab machine shop, we have decided to have Bill Crahen act
   as our point of contact for all FDC job submissions.  This will enable
   us to put together all of our project requests with complete
   documentation and planning.  It will also allow us to have the best
   chance of having our priority work completed with our deadlines.
 - The work on the assembly jigs is in queue in the JLab machine shop.
   They are slated to be completed on August 15.
 - Bill will put together the request for JLab machine shop work for
   our wire frames.  The relevant projects are as follows:
       1). Complete the work already in the machine shop on the two
           aluminum tooling fixtures (modifications of existing plate
           and construction of the second).  This work is slated to be
           completed by Aug. 15.
       2). Cut in o-ring and bolt circle on 4 FDC wire frames.  These
           frames will be ready for machining on September 1, 2008.
       3). Manufacture tool to hold wire frames on 5-axis mill to cut
           out recesses for amplifier boards.  This work will be based
           on a drawing provided by Brian Kross.  This tool should be
           ready for use by the second week of September.
       4). Cut in recesses for amplifier boards into the 4 FDC wire
           frames after the o-ring and bolt circle work is completed.
   Items 2, 3, and 4 should be completed by the second week of
 - Bill has a number of smaller projects that could be completed most
   quickly using the machine shop at FSU.  He will contact Paul Eugenio
   to find out priorities for FDC jobs.  In particular, he has in mind
   have the FSU machine shop handle the pieces for the new flatness
   measuring system.

Wire Frame Construction

 - Brian circulated a construction plan outline for the wire frames.  As
   there was no additional feedback since the report was circulated and
   reviewed last week, this plan is our baseline construction approach.
   Our goal is to have the 4 wire frames for Phase 2 winding done by the
   second or third week of September.
 - Brian will work to formalize the agreement for use of the A-frame
   for frame construction using the frame that Tim found.
 - Fernando discussed the plans for electrical/HV checking of the STBs
   and HVTBs.  This work will be carried out with Herun.  All STBs and
   HVTBs need to be checked before construction begins.
 - Anyone that has items that they know need to be ordered for the FDC
   full-scale prototype effort must contact Elke to let her know the
   plans, otherwise money most likely will NOT be available.  One thing
   that we did discuss were the LV cables and signal cable connectors.
   Fernando and Kim will work on preparing this information and placing
   the order.

Wire Frame Design

 - Due to the height of the solder connection between the cathode board 
   and the rigid flex assembly, as well as the height of the rigid flex
   cable itself, Chuck has laid out pockets to be cut out of the back of
   the wire frame G10 skin.  These cut-outs (positioning and dimension)
   should be vetted through both Roger and Bill to be sure that all folks
   are satisfied.

Spacer Design

 - To allow better clearance for the cathode board rigid flex assemblies
   on the cathode that faces the wire, Chuck needed to shrink the radial
   extent of the spacer ring.  The design has put the edge of this spacer
   too close to the bolt holes for Bill's comfort.  He raised the issue
   of possibly changing the design of the spacer from a composite design
   back to solid polyethylene.  He stated that this would make the
   worries about its mechanical strength moot while making it much easier
   to include the gas inlet and outlet ports.  As the radiation length
   of CH2 is comparable to the composite, we took this suggestion
   seriously.  Bill will do some calculations and give us a recommendation
 - One aspect of the discussion on CH2 vs. composite is the different
   thermal expansion coefficients for the different materials.  Bill
   will do some calculations in this area to understand the issues
   that could arise.

Cathode R&D

 - There was some question about the thickness of the cathode plane foam
   core thickness (3.4 mm vs. 4.0 mm).  Chuck will revisit what is
   included in the CAD model to address this.
 - DSC has prepared a more detailed draft of the cathode R&D planning
   document.  Chuck has started to incorporate this into the project
   planning software system (like a Gantt chart).  We will meet next
   week to come up with a time line that can be sent around for feedback.
 - Bill has essentially finished the design drawings for the upgraded
   cathode flatness measurement system and is ready to start preparation
   of the PR.  This should be done this week.  The system will employ
   an old granite table sitting in the bone yard that belongs to Hall B.
   This table will be used to define the flatness of the cathode support
   ring.  The table is 4 ft (w) x 6 ft (h) x 1 ft (d) and weighs a
   butt load (an SI unit of measurement).  Bill will ensure that all
   relevant safety issues are dealt with in the design.
 - The parts that will be ordered for the flatness measurement system
   will take about 2 weeks to arrive. Bill will plan on putting the
   system together once everything shows up.
 - Micah is continuing to work on the laser head control software for
   the measurement system and things are coming together.  Micah has
   gathered some limit switches for the system that is in place now,
   but these will be replaced with new ones that Bill will order.
 - We will have to work out a time-sharing plan for the laser measurement
   head for the flatness measurements and the tension measurements.
 - Cathode tension measurements have been carried out by Eugene and
   Micah using the high tension cathode plane.  For this work, they used
   a 1.9 kg Al disk, 266 mm diameter on the top of the foil, at its center 
   and measured the foil sagging with the laser, in 2 radial positions "r". 
   The internal radius of the fiberglass ring is R=503 mm.  The measurement 
   was done along the copper strips.
     r          sagging           T
   221+/-5mm     3.73+/-0.05mm  650+/-20 n/m
   347+/-5       1.53+/-0.05    720+/-40 n/m
   The formula used: sagging=m*g/(2*pi*T)*ln(r/R).  The Young's modulus of 
   Kapton is 2.5 GPa.  The relative elongation of the 25-um foil (neglecting 
   the copper plating) is 1%.
 - Eugene is working to define the allowable surface flatness variations
   for the cathodes.  What can we tolerate and still deliver a system
   that can meet the resolution requirements for the cathodes and the
   wire plane?  Eugene will give a detailed update on his work either
   next week or the following week.
 - We have discussed in the past about using a weight to lock in a 
   specified tension into the cathode plane during construction.  Based
   on the above tension measurements, it look like at 100 kg weight would
   the maximum weight needed, obviously less if we go for a lower tension
   cathode version.
 - We discussed alternative techniques to measure the cathode plane tension
   that do not involve putting material in contact with the cathodes.  One
   is to induce a vibration in the cathode using an air puff or a speaker.
   We have a rough plan sketched out for how this could proceed.  Another,
   perhaps more attractive technique, is to seal the cathode plane against
   a surface and provide a slight overpressure.  The measured bulging would
   then provide the tension.

Test Frame Wire Winding

 - IUCF has now started work in earnest on the continuation of the Phase
   1 winding project.  IUCF has figured out how to use the masks and
   the Moire pattern technique to locate wires that are not positioned
   accurately on the winding table.  The masks that we had made arrived
   at IUCF last Friday (this all happened very quickly thanks to Kim
   and Roger).  They have compared the Moire pattern results from one of 
   our existing wire planes to the wire position data and have seen good 
   correspondence.  IUCF is ready now to wind the table with the W and CuBe 
 - The wire frame sag transverse to the wires has been measured to be
   3 to 4 mils (max).  IUCF does not have an easy way to eliminate this
   effect.  Therefore the wires will ultimately not lie in a plane when
   the frame is assembled into a stack.  Keith and DSC discussed this 
   from an electrostatics point of view and believe that this should not
   affect the electrostatic stability of the chamber.  This effect should
   be within our coordinate resolution budget for the cathode planes.
 - The current plan is for IUCF to wind the table and check the wire
   positioning on the table and then to contact DSC before gluing the
   wires to the frame.
 - 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.
 - As the time to complete Phase 1 and Phase 2 winding before the end
   of the fiscal year will be super tight, DSC will work with Elke to
   complete as much of the required Phase 2 paperwork as we can in the
   next few weeks so that we can move quickly to getting Phase 2 in
   place before time runs out.

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.

Cooling System Tests

 - Bill and Fernando completed the planned cooling system measurements
   for the daughter boards.  Fernando is working to put together a
   document of the test results.  He indicated that no further cooling
   system tests are planned until we have more cards and can test a
   bigger portion of the system.  So far, things are working according
   to expectations.

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

 - 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 (essentially) and work is ongoing to finalize
   the test results in the document.  What we have so far is posted as 
 - 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.


 - 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.

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.