Minutes 3-28-2007

From GlueXWiki
Jump to: navigation, search

FDC Weekly Meeting

Date: March 28, 2007

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

Next Meeting: Wednesday, April 4, 2007 @ 1:30 p.m.

FDC Budget

 - Work continues to update the budget for the nominal FDC system
   design.  This update of our Dec. 15, 2006 version (GlueX-doc
   735-v1) is needed for the CD-2 review.  It is due to Elke and
   Elton early next week.
 - The remaining issues for the budget justification document for
   the nominal design are as follows:
    > Brian Kross is working to provide an estimate for the CH2
      spacers and associated machining.
    > Brian Kross is working to provide a more ``official" version
      of the JLab shop estimate for the G10 frames.
    > Brian Kross needs to provide a cost estimate for the stainless
      steel gas ports (inlet and outlet).
    > Brian Kross needs to provide a cost estimate for the plastic
      wire frame storage containers (to be shipped to FNAL).
    > Tim Whitlatch needs to provide a cost estimate for a shipping
      bed for the chambers in their drive back from FNAL to JLab.
    > Joe Beaufait needs to provide a cost estimate for the updated
      LV system.
 - Note that cost estimates should include emails from vendors, 
   quotes, or the basis for the cost estimates.
 - In preparing the FDC budget, we are concerned their there may be
   some cost items whose price may be significantly more than we
   are assuming.  This is the case because we are working on the
   design to minimize the amount of material in the active and
   inactive portions of the chambers.  In our budget there are two
   such items.  (i). Redesign of the cathode flex boards, (ii). Redesign
   of the chamber frames.   The current status of each item is as
    (i). Cathode flex boards: We are working to consider a design of
         the cathodes that replaces the copper with aluminum to reduce
         the material thickness.  This is a tricky item to price out
         as PC board manufacturers will not touch aluminum and we are
         trying to get pricing information from lithography sources.
         Brian Kross is working to come up with some contacts so that
         we can make a pricing guess.
   (ii). Chamber frames: We are working to replace the 5-mm thick G10
         frames with a composite design (fiberglass, carbon fiber,
         and Rohacell).  The average thickness decrease is roughly a
         factor of 3.  Tim Whitlatch and Brian Kross have requests out
         to separate manufacturers and they will come back to us in
         the next few days.  It is already clear that the costs will
         be significantly higher compared to G10.
 - Strategy: Even though we are pricing our nominal FDC design, we
   will assign a higher contingency for these two items, as it seems
   clear that our nominal design is most likely going to change.  We
   will also discuss with Elke about whether we should replace our
   current design with the new modifications.

Magnetic Field Issues

 - Brian has heard back from his contact at BNL regarding a magnet.
   They have a candidate and will look to see if the power supply still
   works.  Brian indicated after the meeting that the magnet is the
   48D48 dipole in the AGS.  More to come.
 - Brian will follow up with Elke regarding her contacts in Hamburg.
   He did give all of the relevant information to her.
 - Simon has been working on literature searches to find out what
   gas mixtures are being used in the cathode chambers at ATLAS,
   CMS, PHENIX, LASS, etc.  He has been performing GARFIELD studies
   of the Lorentz angle.  His primary area of investigation so far
   has focussed on argon/CO2 mixtures with roughly 50% of each gas.
   For these mixtures, the Lorentz angle maximum in our drift cell
   is about 20 deg.  This is a factor of 3 reduction from that
   computed for the 90-10 mixture.  More work to come.
 - We are planning to have a phone conference with Andrey Korytov 
   from the University of Florida (CMS CSC expert) on Tuesday of
   next week.  Simon will circulate details of the meeting.  This
   meeting will primarily focus on magnetic field issues in our
   cathode chambers.  DSC has prepared an agenda/talking points for
   this meeting and will circulate them shortly.

FDC Design

 - Both Tim and Chuck produced CAD drawings (real CAD and ``foot CAD")
   for us to discuss.  Tim focussed on a picture of the connector
   placement with the 5-mm half gap.  Here the preamp daughter board
   connectors on the wire plane are mounted on the STB with no
   cut-outs on the G10 support frame.  For the cathodes, the connectors
   are placed on the back side of the cathodes (where the Rohacell
   used to live).  Chuck produced a new version of the 3-D picture
   showning all four FDC packages focussing on the placement of the
   connectors around the perimeter of the FDC with the new +/- 75
   degree cathode strips.  The connectors now are also placed between
   the rails on the under-side of the FDCs.  This is still a work in
   progress and he is optimizing the placement.  
 - Note that we are presently investigating splitting the central
   cathode strips in half (with readout on the ends) to reduce the
   rate issues on these chambers.
 - We still need insight from David about the size of the beam hole
   in each FDC package that we will deaden to provide coverage down
   to 1 degree.  Once this is determined, we need to revisit the
   rates on the strips and the wires as a function of z-location
   of the packages.
 - We still need input from Fernando on how to get the cathode
   signals to the back side of the cathode planes.  We want a robust
   connection from the front to the back.  An important issue may
   be the quality of the vias with very thin conductive layers.
 - We discussed the cathode design option with no Rohacell backing.
   An important issue is the electrostatic deflection of the cathodes
   without backing.  We have to keep the tension on these planes to
   a minimum to reduce the effect of lateral distortions of the
   strips.  However, the lower the tension, the bigger the distortions.
   Simon has done some calculations of the deflection as a function
   of tension, but we have no clear idea of what the tensions on
   the cathode surface will be.  Tim and Brian brought up the idea
   of performing measurements with strain gauges to connect to the
   calculations that Simon has done.  This all seems possible, but
   because there needs to be a definitive answer, Brian will provide
   a write-up of a test plan to complete the measurements.  Of course
   we need input from Simon on the maximum possible deflection to
   ensure the cathode and wire plane measurements are well within
   our tolerances.  More to come.  Tim will also consider performing
   some simulations with IDEAS.
 - We discussed possible approaches to mitigate the effect of the
   cathode distortions due to electrostatics.  One idea is to bias
   the ground planes.  We need to talk to Fernando and Gerard about
   the impacts of this possibility.  We could also rely on maintaining
   a certain differential gas pressure across the cathodes to balance
   the electrostatic deflections.  This seemed like a more dicey

Cathode Mechanical Mockups

 - New dummy cathode frames have arrived.  Brian has performed some
   initial QA checks.  He noticed 3 ``stripes" in the cathode surface
   that appeared on the boards.  These could have arisen due to the
   rolling procedure or the manufacture procedure.  Brian is in
   contact with the company to learn more about this.  However for
   the majority of the board surface, Brian was quite pleased with
   the quality.
 - Simon will get a sample of these cathodes and will perform
   measurements of the strip-to-strip capacitance.  He will talk
   to Gerard about what other measurements would be useful to perform.
 - Simon will also talk to Joe about getting his capacitance
   measuring instrument.  As Gerard is in town for the Collaboration
   meeting, he should take the opportunity to talk to him directly.
 - Brian has begun work on the next cathode sandwich mockup.  He will
   begin with the design without the Rohacell backing.  Before 
   tensioning the cathodes, he will arrange to get them measured so
   that we can compare these numbers to the post-tensioning measurements
   to quantify the distortions.
 - After Brian completes the cathode sandwich without the backing, he
   will then construct a second cathode sandwich with the Rohacell.
   Of course he will employ the techniques developed during the first
   cathode sandwich construction, but there still are some issues that
   need to be worked out.  This may lead to some modification of the
   tools and equipment.

Circuit Board Design

 - DSC asked Kim to provide a rough layout of the HVTB design for
   the full-scale prototype.  Kim asked a number of questions to make
   sure that she understood the requirements.  Simon will provide
   Kim with a part number for the HV Reynolds-type connectors.
 - Although Roger was not present at the meeting, we asked Kim to
   talk to him about the status of the design of the +/-75 degree
   cathode boards for the small-scale prototype.  We also need to
   investigate if we need new G10 support frames (although we have
   4 of the current design in stock).  We would like these designs
   for initial review in about 2 weeks.

Summer Student

 - It looks like there are no more college students available to
   work on the FDC project.  We are still looking into this.  Kim
   suggested that we pursue a summer hire.  This will be investigated.


 - DSC sent the current draft of the FNAL MOU to Karen Kephart at
   FNAL for initial (non-official) review.  The two of us need to
   iterate on this before we start walking it through the JLab
 - Elke stated that it makes sense to get this MOU in place as soon as
   we can.

Small-Scale Prototype Work

 - Given that we expect the +/-75 degree cathodes to be available within
   about 2 months, it may be that we will not need to worry about employing
   the 90 degree cathodes.  They are available to install, but installing
   them will be put on hold for now.  It may be that we will install them
   at some point to get some more information to check Simon's calculations.
 - Simon has been studying a modified argon-CO2 mixture in the small-scale
   prototype consisting of a 40-60 mixture to understand the impacts on
   chamber performance on the cathodes.  He also needs to be able to very
   soon quantify the impact on the time-to-distance calibrations and the
   impact on the resolution in the wire plane.

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