Minutes 1-17-2008

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FDC Weekly Meeting

Date: January 17, 2008

Participants: Daniel, Brian, Simon, Roger, Chuck, Fernando, Bill, Mark

Next Meeting: January 24, 2008 @ 1:30 p.m.

Composite Wire Frames

 - The finishing touches on the 3 wire frames that will be sent to
   IUCF for winding are being made in the machine shop.  Brian reported
   that the frames will be done this week.  He is fully satisfied with
   the quality of the frames.

Wire Winding

 - The PR is awaiting Allison's signature at the current time.  After
   she signs this, everything will be turned over to the JLab procurement
   folks.  When they have completed their review, they will make any
   necessary changes and then contact the procurement folks at IUCF.
   Updates will be provided to the group as soon as we know something
   on signing the wire winding contract.

Composite Cathode Construction

 - Brian and Denny will begin work on Monday to construct our first 
   composite cathode boards and composite cathode sandwich using the 
   dummy cathode boards.  Brian will employ available low-density
   Rohacell foam for the frame core that will not be the thickness of
   the final design, however this was not thought to be a major concern
   for what he is trying to do.  Starting this work has been delayed
   because the aluminum tooling plate needed was being used in the shop 
   for preparation of the composite wire frames.
 - We still do not have a clear idea how we can measure the flatness
   of our cathodes.  Bill has been doing some research to find out
   what is possible (remember a non-contact technique is required).  We 
   would prefer to outsource this if possible instead of developing an 
   expensive system here at JLab.  It may also be the case that we might 
   only need to measure the first few cathodes to be fully confident that 
   we can make the planes within our flatness specifications.  If this can 
   be done, we would not have to measure each and every plane that we made.

Small-Scale Prototype

 - Next week, Brian will mount the +/-75 deg cathode boards on their
   associated frames for the small-scale prototype.  At the current
   time, we believe that we have solid knowledge of how the cathode
   resolution depends on the orientation of the strips relative to
   the wires.  The bigger issue that we need to study is the performance
   of these cathode boards with 2-micron thick copper strips.  All of
   the boards studied for the small-scale prototype to date have a
   5-micron copper thickness.
 - Once the new boards are available, Simon will install them into the
   test chamber for evaluation.
 - Starting next week, Simon and Fernando will acquire a gallery of
   pulses from the chamber read out with the ASIC preamplifiers.  This
   gallery will then be supplied to Gerard and Mitch for study.

Package Gas Volume Definition

 - As discussed at our last meeting, we are working to redesign the
   FDC packages to be a single gas volume instead of 6 separate volumes.
   This was felt to be the right thing to do to ensure that the
   differential gas pressure across the cathodes was zero.  Roger
   will look at the design of the cathodes and where we can include
   through-holes.  These through-holes would then be matched with holes
   in the Rohacell backing layer.  The only tricky issue is how to
   get the gas around our thin ground layers (that go between neighboring
   cathodes).  Brian will look into this design and come up with a plan.  
   Presently he believes that he can incorporate gas holes in the support 
   frame, but he needs to look into this.  As a result of this change, we 
   will need to incorporate gas windows on the upstream and downstream end 
   of each package.  If we use this approach, it will simplify the
   gas connections to each package.


 - Kim is nearly done with the design of the STB and HVTB boards.  The
   full set of design drawings has been turned over to Fernando for
   review.  When Fernando gives his blessing, Kim will need several days
   to complete the layout.  She will then start the procurement process.
   We need to decide how many sets of boards we want to order.  Kim
   will also place the orders for the components and connectors.

Cathode Daughter Boards

 - Since our last regular meeting, Roger completed his preliminary layout 
   for the cathode daughter boards.  He then ordered parts to build
   several mechanical mockups.  The mockups included a 1/32-in thick piece
   of G10 with a cut-out in the middle of it (this represents the cathode
   support skin).  The back side of this piece of G10 included copper
   pads to which the rigid flex cable was soldered (these pads would be
   the cathode board itself).  On the front side of this piece, the
   rigid flex cable was soldered to Roger's cathode daughter board and
   the preamp daughter board connector was attached.  The flex cable was 
   soldered to the back side of the daughter board using a solder re-flow 
 - The prototypes that were made up were passed around for discussion and
   the design looked very professional and stable.  Roger will have to
   make some minor modifications to the cathode daughter board to allow
   room for the power cable connector (the same ERNI connectors that are
   being used on the wire frame boards).

Cooling System

 - Bill gave an update on the cooling system.  He has gotten a quote
   for the construction of the 530 copper brackets that attach from
   the preamp daughter cards to the cooling lines.  The price was a
   bit steep at about $14k (or about $30 per bracket).  He will look
   at his bracket design and see if he can modify the design to reduce
   the costs.
 - Bill has also been looking for a chiller system that will be
   compatible with our cooling power requirement and our desire to
   use Fluorinert as our cooling medium.  He is not having much luck
   finding a cost effective system.  He will continue to look.  If we
   were planning on using water as our medium, there would be many
   reasonably priced chiller options, but we are all nervous about
   water given the ever-present possibility of leaks.

LV/HV System Design

 - Earlier in the day, Fernando and DSC met with Joe Beaufait to discuss
   the design of the FDC high voltage and low voltage systems.  We 
   discussed the overall concepts and design philosophies of each system,
   including how ground will be handled.  We reviewed the granularity
   in both systems and discussed the layout of the fusing system for
   the low voltage control.  We will meet again with Joe in about 2
   weeks to give him a chance to start thinking about these systems and
   come up with firmer plans and layouts.  When we make a bit more progress
   on a preliminary layout, we will get the CDC folks involved to be sure 
   that we have a system that will work for both chambers.


 - 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.

FDC Mini-Review

 - The FDC mini-review on technology choice is scheduled for Feb. 1.
   The reviewers will be Howard Fenker (JLab) and Larry Weinstein (ODU).
   DSC has prepared a new version of the FDC Technical Design Report
   to reflect the current system design.  This will be provided as part
   of the pre-briefing material.
 - The planned speakers for this review are Mark Ito (physics overview
   and needs), DSC (FDC design), Simon (FDC R&D, measurements, and
   algorithms), and David (GEANT3 simulations).  There will be a planning
   meeting for the mini-review next Thursday where we will start to
   look at the slides for the different talks.

FDC Insertion and Cabling

 - At the collaboration meeting there was talk that it may be preferable
   to have the FDC inserted from the upstream end of the solenoid rather
   than the downstream end.  This would also mean that all of the readout
   and power cables would come out of the upstream end of the magnet.
   This may be important to remove the problematic FDC cable mass that
   gives rise to lots of photon conversions that lead to a coverage hole
   between the BCAL and FCAL.  More simulation work and discussion is
   needed before a final decision can be made on this issue.  However,
   we did have some preliminary discussion on the design work that would
   be required for this scenario.

Schedule Discussion

 - During the collaboration meeting Elke raised the idea of giving
   Mitch more time to work on the next version of the ASICs.  The
   original plan was to give Mitch feedback on the current ASIC version
   (called GAS-1) by March so that he could complete a design and
   submit it by April.  The next submission deadline for the chips would
   be June, which means that we would not have any real quantity of
   amplifiers before December.
 - This issue is relevant for testing of the full-scale FDC prototype.
   How many amplifier boards will we have?  Will we have sufficient
   numbers to carry out a full test plan of the FDC performance to
   finalize the system design?  If we have sufficient numbers of ASICs,
   we still have very few ADCs and TDCs.  If we do not have the necessary
   amplifiers and readout electronics, we may decide to scale back what
   we will build for the prototype.  It may be most sensible (and cost
   effective) to build a half package prototype.  More discussions will
   be forthcoming on this front.

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.