Minutes 3-5-2007

FDC Weekly Meeting

Date: March 5, 2007

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

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

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FEA Analysis

 - Tim has completed a round of finite-element analysis for the
   deflections to our wire frames for a number of different scenarios.
   These includes board 5-mm and 6-mm thick with no cut-outs for
   daughter board clearance and for a 6-mm board with the cut-outs
   included.  He assumed tensions of 20 g and 130 g for the sense
   and field wires, respectively.  The total wire load is about
   32 lbs.  He also included a semi-realistic overhang of the PCB on 
   the inside perimeter to allow for the capacitors to be included on 
   the back side of the PCB.
 - For the 5-mm and 6-mm thick wire frames, the deflections in the
   directions along the wires and perpendicular to the wires are
   below about 100 microns.  For the 6-mm thick design with the
   cut-outs for clearance, the maximum deflections are below 300
   microns.

Design Issues

 - Based on the FEA analysis, we discussed again the basic design
   for the wire frame.  First we will move to design a wire frame
   that is 6-mm thick, has the cut-outs for clearance for the
   daughter boards and connectors.  We still need to understand
   the deflections that are present with the final inside perimeter
   overhang.  The capacitors will be placed on the back side of
   the STB, but above the top of the solder pads.
 - The design of putting the cathode preamp connectors in the 
   middle of the cathode sandwich is too technically risky and
   we will drop this idea.
 - With the 6-mm thick wire frame, we will only have to machine
   the G10, and the not STB PCB.  Thus will we have a continuous
   frame for support.
 - Fernando has found a daughter board connector that is only 4.2 mm
   thick.  He will pass the specs onto Tim and Chuck and they will
   consider this as nominal for proceeding.  This new connector
   is wider than the previous connectors that Fernando had found,
   namely 1.8-in wide compared to the old number of 1.5-in wide.
   This new wider connector will allow for the radial length of the
   daughter boards to be reduced.  Thus these connectors will be
   moved out radially, giving more room for traces and components.
 - The cathode design has been modified.  We have decided to set
   the U and V stereo angles at +/- 15 deg with respect to a line
   perpendicular to the wire plane.  The old values were +/- 45
   deg.  Chuck has some work to do to figure out the placement
   of the connectors and problems with the gas port clearance
   and locations.
 - We also plan to make the pitch of the strips in the middle of
   the plane smaller to be able to handle the rates.   The width
   to modify is +/- 5 cm about the middle of the chamber.  The
   new pitch should be 2.5 mm with a 1-mm gap.  How this design
   modifies the design and/or channel count will be studied by
   Chuck.  We need to optimize this.
 - The time line is for Chuck to finish placing the connectors
   after getting new dimensions for the daughter boards, and then
   for Kim to work to perform a realistic layout of the STBs.
 - DSC asked Kim to rough out the HVTB so that we can work on
   understanding the real estate issues and the mechanical design
   issues.
 - DSC asked if we could aim to have the STB and HVTB design
   complete by the end of April.

Small-Scale Prototype

 - Brian has completed manufacturing the strip planes that are
   at 90 deg with respect to the wires.  They are ready for
   installation now.  DSC asked that Simon complete the resolution
   studies with the reworked grounding configuration for the
   chamber (done during Gerard's visit in January).

Wire Winding

 - During our visit to FNAL in January, a question came up regarding
   the relative heights of the wires.  It is acceptable to have
   both sense and field wires in contact with the solder pads, or
   do we need to raise the sense wires to be coplanar with the
   field wires?  We need to do the calculations to address this
   question.

Drift Chamber Review

 - The DC Review begins tomorrow.  The chamber frames and cathode
   mockups will be brought in for show 'n tell.

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