Minutes 1-31-2008

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FDC Weekly Meeting

Date: January 31, 2008

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

Next Meeting: February 3, 2008 @ 1:30 p.m.

Wire Frame Status

 - Brian reported that the JLab machine shop has completed work on the
   three wire frames that are to be sent out for the test winding.  Brian
   will put these frames into the frame transport box that was delivered
   some time ago.  He has some minor modifications on the box to add some
   foam bumpers, but this is minor work.

Composite Cathode Discussion

 - The first composite ring has been constructed and the second composite
   ring to make a cathode sandwich is under construction.
 - We discussed plans for making the connections to the ground plane.  One
   option that seemed reasonable was to embed several small copper bars into
   the back G10 skin of the cathode ring.  As we have to ground both sides
   of the ground plane (it is double sided), we will use conducting epoxy
   to make the connection.  As slip connector (or friction connector) will
   be soldered onto these copper bars and we will include connectors
   soldered onto the STB and HVTB boards and run one (or several) jumpers
   from the ground plane over to the wire frame boards.
 - The first composite cathode will not include this aspect of the design
   as Brian has other things to focus on in laying out the cathode boards.
   His plan is to build a second composite cathode sandwich and to include
   a design for the connections to the ground plane.
 - In adding the 2-mm thick Rohacell foam backing to the cathode board,
   Brian is planning to spray on a thin layer of epoxy to the cathode
   board and then to install the foam sheet.  This will be weighted down.
   After the epoxy cures, he will seal the gap between the foam disk and
   the G10 cathode support frame with a bead of epoxy.
 - In our current plans, we want to remove the Kapton and foam backing
   from the central beam area.  We will begin discussions with the circuit
   board manufacturer (Sheldahl) if this can be done on their end.  If not,
   it has been suggested to use a laser cutting tool.  Bill has some
   contacts in the business and will look into this idea.
 - We discussed a specifications document for the cathode flatness
   measurements.  Bill was given all the information on requirements during
   the meeting and he will prepare a document reflecting the plans and
   circulate for comment.
 - We will ask Roger to handle all aspects of cathode board and cathode
   daughter board procurement.  Roger will make contact with the circuit
   board manufacturers regarding flatness specs, handling, transport, etc.
 - Recently we have found a paper on a cathode strip chamber that employed
   0.15 micron electrodes on their cathode surface.  Simon knows one of
   the folks on the paper and will make contact to find out what was done
   and how the device performs.  Roger should have another discussion with
   Sheldahl on the thinnest cathodes that they can make.
 - Given the new idea to have each package as a single gas volume, Brian
   will come up with a sketch to indicate how to allow gas flow around
   the ground plane.  The initial idea is to allow a lip on the inside
   edge of the G10 skin that supports the ground plane (of the same size
   as that on the wire frame) to epoxy the ground plane in place,  We can
   then allow for holes through the skin to allow gas flow.  Roger will
   give us information on available real estate for holes through the
   cathode planes.  Certainly the beam hole is available where there are
   no copper strips, but there is space on the sides of boards too.
 - Bill has been in contact with Dave Meekins who has volunteered to perform
   our hydrodynamic flow calculations for the FDC packages to ensure that
   there are no impedance or mixing issues with our gas volume design of
   the FDC packages.  Some linear combination of Bill and/or Chuck will
   provide a model to Dave who then will begin on the work shortly.
 - We discussed further the notion of where to put the gas ports.  Nominally
   we plan to include an input on the gas window frame on one end of the
   chamber and an output on the opposite gas window on the opposite side
   of the frame.  This is not yet final and we will work to come up with
   a plan.

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.

Wire Winding

 - There has been some progress on things from the JLab end and we
   expect to be in contact with the procurement folks at IUCF within
   rough 1 to 2 weeks.  As there is news, updates will be given in the
   FDC meeting minutes.

Cooling System Update

 - Bill has completed a block diagram and rough design for the chiller
   system for the preamplifier cooling system.  We have not finalized
   a placement for this system, however, it is important to minimize
   the length of the cooling runs.  We need to discuss with the group
   where this system can be located.
 - The chiller system included interlocks on the flow, the temperature
   of the return, and the coolant reservoir.

STB/HVTB Stuffing

 - We discussed issues associated with board stuffing.  Fernando made
   it clear that we should stuff all the circuit boards prior to
   wire frame assembly.  This is important for the easiest stuffing,
   but probably more importantly from the standpoint of being able to
   clean the boards.  This stuffing could be done in house, but Fernando
   preferred the idea of sending this out to a board house to follow
   best practices.  Also there will be board stuffing after the winding
   is completed to include the preamplifier board connectors and the
   HV components.  This will be done in house as we will not be able to
   transport the wound frames and certainly it would not be wise to have
   outsiders handling them.
 - We agreed that we need to define a board stuffing procedure and
   board cleaning procedure no matter where the boards are stuffed.
 - 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.
 - 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.

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.

Joint FDC/CDC Meeting

 - We will have a joint FDC/CDC meeting next week at a time to be
   determined.  Once the meeting is set up, DSC will circulate an email
   with the information and the agenda.

FDC Construction Space Request

 - We have been asked by Elke to prepare a space request for the FDC
   construction, testing, and storage requirements.  DSC will prepare
   a draft and circulate for feedback.

FDC Mini-Review

 - The mini-review for technology choice for the FDC system will take
   place tomorrow (Feb. 1).  Mark, DSC, Simon, and Dave will be giving
   the presentations.  The reviewers are Howard Fenker and Larry Weinstein.
   The observers from the 12 GeV office are Rolf Ent and Allison Lung.

Meeting on ASICs

 - Fernando is trying to arrange a meeting with Mitch Newcomer will the
   FDC representatives, the CDC representatives, and Gerard Visser.  This
   meeting will be announced as soon as it is set up.

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.
   It may be that the prototype will not have the full number of layers
   of the final design.  DSC will be in discussion with Elke as we get
   closer to procurement.
 - We will need to provide Elke with detailed information on what we
   want to purchase and the associated costs.


 - 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.