Minutes 2-7-2007

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FDC Weekly Meeting

Date: February 7, 2007

Participants: Daniel, Tim, Roger, Fernando, Kim, Simon, Brian, Elke, Chuck

Next Meeting: Wednesday, February 14, 2007 @ 1:30 p.m.

Design Issues

 - At last week's meeting we discussed a current issue with the design
   regarding the space available for the daughter board and connector
   on the cathode plane face that is closest to the anode board.  Presently
   there is no straightforward way to fit these connectors in without
   trimming down the g10 spacer or adding clearance notches to the anode
   board.  None of these solutions is ideal and all of the solutions
   suggested so far would lead to a weakening of the boards which would
   increase flexing and bowing.
 - Fernando will look into trying to find thinner connectors for the
   daughter boards.  We need to find connectors thinner than about
   5.2mm to avoid having to cut into the back of the wire plane g10
   frame.  Fernando thinks that this is possible and will look into it.
   He stated that he is very much against having to machine the connectors
   thinner.  He believes that this would destroy their integrity.
 - It became clear as the discussions continued that we will have some
   problems with clearance no matter the thickness of the daughter board
   connectors.  DSC suggested a separate concentrated meeting on this
   issue with a subset of the FDC team.
 - As stresses on the g10 frames are a possible issue, Tim will look into
   carbon fiber.

Design Rules

 - DSC has prepared a list of PC board design rules that has now been
   looked over by Fernando.  After the meeting DSC sent these off to
   Kim and Roger so that they will have some general guidance on how
   to produce the STB and HVTB boards for the FDC.

Cable Layout

 - Due to access issues with the daughter boards, we decided to keep the
   signal cables located from rail to rail.  In the space under the rails,
   we will pack the HV, LV, gas, coolant lines.  This will lead to roughly
   uniform material thickness around the system.
 - Chuck has prepared a new drawing showing a single FDC package and
   the cable locations.
 - We could not discuss this more without Joe B. being present.  We will
   come back to this at our next meeting.

Daughter Board Design

 - We revisited the daughter board design.  Fernando suggested that we
   consider as nominal a 50-pin connector for the cathodes (this will
   give compatibility with the FADC) and 34-pin connector for the
   anodes (to give compatibility with the TDC).  Before we worry too
   much about these details, we need to make a final decision on the
   readout.  If we can achieve sufficient timing resolution with the
   FADC with a simple, CPU-acceptable algorithm, we may still decide
   to use the FADC on the anodes.
 - For now Fernando has designed the board with 3 ASICs.  We will worry
   about the 2 ASIC daughter board later.

Engineering Work

 - Tim has done a number of calculations of stress and thermal environment.
   DSC will schedule a separate meeting with him to go over this work.

Ground Plane Thickness

 - Brian provided Gerard Visser with a sample of our ground plane material
   (6.3 micron Al-mylar).  Gerard will let us know if this material is
   appropriate for our use in the FDC.

Cooling System

 - DSC asked Tim to start a design for a liquid-coolant system for the
   FDC electronics.  Tim will begin a layout and will work with Fernando
   to get new thermal simulations completed to optimize the design.
 - Tim suggested a water-cooled system as these units can be bought
   off-the-shelf without any real design work required.

Cathode Mechanical Mockups

 - The first full-scale cathode sandwich has been completed using bare
   kapton for the cathode boards.  This has been delivered to the
   JLab Survey group for measurements of flatness.  These measurements
   should be completed by Friday.
 - DSC asked Brian to prepare another cathode board using the tensioning
   system as an alternative to the Rohacell backed version.  At issue
   is the multiple scattering contribution due to the Rohacell.  Brian
   will begin work on this shortly.

Preparations for DC review

 - The drift chamber review that will include the CDC and FDC has been
   scheduled for March 6.  In preparation for this review, we need to
   prepare a technical design document for the FDC.  DSC and Simon will
   prepare an outline and then folks will be asked to provide writeups
   to be included in this document.  This includes Brian: Gas, cathode
   sandwiches; Fernando: thermal simulations, daughter boards, Tim:
   Cooling system, stress calculations; Simon: prototype studies, shaper
   studies; DSC: FDC design, MC.  Emails for requests of specific
   sections will go out shortly.

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