Minutes 2-7-2008

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FDC Weekly Meeting

Date: Feb. 7, 2008

Participants: Daniel, David, Mark, Simon, Roger, Brian, Elke, Kim, Chuck, Fernando, Curtis, Yves, Paul, Matt, Bill, Tim, Elton, Gerard

Next Meeting: February 14, 2008 @ 1:30 p.m.

Test Frame and Prototype Wire Winding

 - The purchase request for the Phase 1 and 2 wire winding has been
   signed by Allison Lung and passed onto the procurement folks at
   JLab and IUCF.  The IU procurement office is reviewing the documents
   and providing a final budget.  We expect that a signed contract for
   the wire winding will be in hand within the next several weeks.
 - DSC will be in contact with the IUCF folks to finalize a list of
   equipment and supplies that we will need to bring with us.  Brian
   will procure any items that we do not have.
 - Brian needs to check whether he can actually go to IUCF for the
   week of the test frame wire winding given his ISM responsibilities.
   DSC will follow up on this.

Full Scale Prototype

 - DSC is working on a stripped down budget for what we want to
   construct.  The full-scale prototype will most likely consist of
   half a package (U-V-W) only.  Once the final budget is approved
   by Elke, we will begin procurement of the pieces required.

Cathode Boards

 - Roger will take over all aspects of the cathode flex boards.  He
   is already responsible for the design, but he should take care of
   paperwork, procurement, QA planning, etc.  Roger should also work
   now to contact the cathode board material supplier and the circuit
   board company to get them to understand our flatness requirements.
   Why do the boards come to us with clear surface defects and can these
   be eliminated?  We also need to work with these companies to specify
   board handling and transport.

Composite Cathode Discussion

 - Brian and Denny have completed construction of two composite rings
   for the cathode sandwich.  They have used the 1/32-in thick G10
   skins and a 5-mm low density Rohacell core.  They are now working
   on laying out the first cathode boards (3 pieces with the dummy
   cathode boards).  This cathode sandwich should be completed by
   Monday or Tuesday next week.
 - A second prototype will be constructed using our current thinking
   for the attachment and layout of the ground plane.
 - Brian will prepare a construction procedure document with a full
   set of photographs as he constructs the last prototype cathode.
 - Bill circulated a specification document for measuring the cathode
   surface flatness.  This document was discussed and feedback was
   given.  Bill discussed a laser interferometry system that might be able
   to perform our flatness measurement for the cathodes when they are
   in a vertical position (and should work on the Kapton/copper surface).  
   This system could mount to the horizontal milling machine in the JLab 
   machine shop.  This machine has a 40-in movement range.  The system 
   should provide accuracy to better than 50 microns.  The cost for the 
   sensor and software is on the order of $2k.  We would need to develop 
   a frame to support the cathode frame.  Brian and Bill should work
   together to come up with a complete budget estimate for this system
   and the associated measurements.  Brian and/or Bill should talk to
   the JLab shop about the availability of the milling machine for the
   work we want to do.

Gas Window/Frame Design

 - With the new idea of having each FDC package as a single gas volume,
   we need to design the gas windows and frames.  Brian will come up
   with a design and circulate for comment.  When the design is finalized,
   we can have Chuck put it into the CAD model.  We still need to determine
   the thickness of the gas windows.

Cooling System Update

 - Bill is working with Denny and Fernando to put together a test setup
   for the cooling system.  This will include a water-based chiller
   borrowed from Hall A and a cooling loop with appropriate sized plumbing.
   Bill has already gotten several brackets that attach to the preamp
   that will clamp to the cooling loop.  He has brackets made in copper
   and aluminum.  The preamp card will be supplied by Fernando and is
   one of the version stuffed with 3 ASIC chips.  The board will be
   outfitted with a thermocouple for temperature readback.  The board
   will then be packed in some amount of insulation to mock up the
   real FDC environment inside the solenoid.
 - Bill will be in charge of the tests and will take all of the data
   relevant to be sure the cooling system can supply the required
   cooling power.  He will also work to define the flow parameters of
   this water-based chilling system for the ultimate Fluorinert system
   that is planned.  Bill will also document the test setup and take
   lots of pictures.


 - One minor complication that came up is that Brian's assembly jig
   does not allow for components to be on the boards.  He has a clear
   idea of how the alignment jig needs to be modified to handle the
   stuffed boards and will lay out a design for discussion.
 - We will most likely stuff the prototype chamber boards here at
   JLab.  DSC and Fernando will meet with Kim and the folks in her
   building that do this work to go over what is needed.  This meeting
   will take place next week.  We need Fernando to prepare a writeup
   to detail the board stuffing and cleaning procedures.
 - Kim will prepare a QA manual for the wire frames to test them after
   we get them back from the board house.  She will also be responsible
   for initial QA tests.
 - Kim has finalized the HVTB design and the design for one of the STB
   boards.  By tomorrow she should have completed the layout of the 
   second STB.  Fernando will look this over and give final blessings.
   Kim is working to get quotes for all of the wire frame circuit boards.

Small-Scale Prototype

 - Brian will mount the +/-75 deg cathodes for the small-scale prototype
   next week.  Simon plans on installing them shortly after thereafter
   for testing.

Gas Volume Definition

 - We have not yet converged on the gas distribution to the FDC 
   packages.  We had originally intended to feed each layer within a
   package with its own input and output lines.  However, the differential
   pressure across the cathodes that is planned would cause a 
   significant outward bowing of these planes.  We then began to consider
   making each FDC package a single gas volume.  However, there are
   concerns with the impedance and the ability to flow gas through the
   volume quickly. 
 - A new idea came up to keep each chamber layer an individual gas volume
   with the ground plane the barrier.  The cathodes would still have
   holes in the middle and possibly the edges on either side after the
   last cathode strip.  The gas input line for each package would then
   be distributed in a parallel fashion to each layer in the foam
   behind the cathodes.  This design might also call for a slightly
   thicker ground plane to handle any unbalanced pressure load between
   neighboring layers.  We need to prototype this and make a decision
   on what we are going to build here. 

FDC Construction Space Request

 - DSC prepared a space request document for the FDC construction that
   will be given to Elke tomorrow.  This document was reviewed and
   minor changes were added.

FDC Mini-Review

 - The FDC technology choice mini-review took place last Friday.  The
   review committee strongly endorsed our current design with two
   crossed cathode strips imaging the wires.  The final report from the
   committee will be provided in about one week.

Meeting on ASICs

 - Fernando has set up a meeting with Mitch Newcomer and Gerard to
   discuss the current studies with the ASIC and the design plans.  This
   meeting is scheduled for Wednesday Feb. 13 at 2:00 p.m..

Full-Scale Prototype

 - We are working to complete the design of the full-scale prototype
   so that construction can begin in the next month.  What we actually
   construct is predicated on how much money is available in the budget.
   DSC believes that the ABSOLUTE minimum that should be constructed is
   a pair of neighboring layers (4 cathodes, 2 wire planes).  The
   preferable minimum is half a package (6 cathodes, 3 wire planes).
 - DSC will prepare a budget for half a package for Elke to review to
   make a decision based on what is available in the Hall D budget.


 - 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.

Combined FDC/CDC Meeting

 - The first 45 minutes of this week's meeting was a combined FDC/CDC
   meeting to go over issues common to both groups.  The main discussion
   was on preparations for the upcoming tracking and charged particle
   PID review in March.  David is leading the effort on the Monte Carlo
   to connect the physics requirements to the detector design specs.
   Matt Bellis is also working on things more from the PID standpoint.
   One of the main arguments that will be made for the March review is
   to compare the FDC/CDC specs (position, angle, momentum resolution)
   to those for BNL E852.  Our specs are very similar.  If they were
   able to perform successful PWA analyses, then GlueX will also be
   able to at similar levels.
 - Curtis and Yves also discussed the current situation with the 
   CDC prototype tests.  They are presently awaiting delivery of 18-m
   long Spectra-strip cables for test the system.  Another issue with
   the CDC is to develop the algorithms and codes to test the dE/dX
   resolution of this detector.  One thing that is missing is the
   ability to distribute a universal clock to the FADCs so that
   straws from multiple FADC modules can be linked together for a 
   given event.  Kim will work on this clock distribution board based
   on input from Gerard and Fernando.
 - We discussed the idea of z-vertex resolution for the CDC.  One idea
   that Curtis has proposed is to link together pairs of straws at
   the downstream end of the CDC (linking straws that have a low
   probability of firing from real tracks at the same time).  This
   linking could then allow for a charge division measurement to
   fix the z-coordinate of the track with reasonable resolution.  The
   development of these ideas will not happen before the March review.
 - We discussed the notion of routing the FDC cables out the upstream
   end of the solenoid.  The FDC group needs to provide Curtis and Yves
   with the amount of radial real estate needed for the FDC cables and
   cable support structure requirements to decide how many outer layers
   to remove from the CDC (either 1 or 2 layers).

Minutes prepared by Daniel. Send any comments or corrections along.