Minutes 6-6-2007

From GlueXWiki
Jump to: navigation, search

FDC Weekly Meeting

Date: June 6 2007

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

Next Meeting: Friday, June 22, 2007 @ 1:30 p.m.

New Prototype Cathodes

 - Brian has heard from CCT regarding our cathode boards.  They believe
   that they now have a solution to making our boards that involves a
   two-step etching process.  They will require that we pay an additional
   $14k for setup charges to be able to do what we need.  It appears that
   this is a one time charge that would cover both the boards for the
   small-scale prototype chamber, as well as the boards for the full-scale
 - Brian is also working on contacting other board manufacturers to find
   out if they can make our boards and also if they can make the boards
   for our full-scale prototype out of a single piece of materials.  More
   to come.
 - The time line is getting somewhat tight.  We would like to have the
   boards for the small-scale prototype in our hands so that we can 
   complete the studies with the +/-75 deg cathodes before the magnet 
   tests in July/August.
 - Fernando has been in touch with the folks at Sierra.  They told him 
   that they can produce boards with 1 micron of Cu on 1-mil Kapton.  The
   attraction here is that they would also supply the cathode material,
   cutting out the middle man.  The maximum width boards they can make
   is 24 in.
 - Brian will send them a Gerber file of our small-scale and full-scale
   boards for quotes.

Circuit Boards

 - Kim has been improving the layout of the STB boards based on comments
   from our last meeting.  The main issue was to improve the spacing between
   the signal traces at HV and the capacitor legs at ground.  The spacing
   in the current layout looks acceptable.
 - Kim will start roughing out the traces from the resistors to the
   connectors as a check on real estate.
 - Fernando showed us a connector and cable that he has selected for
   making power connections to the STBs for the daughter boards.  
 - We discussed LV bussing options and possibilities.  It may be that we
   want a distribution panel on the downstream face of the last FDC
 - Fernando asked that we provide a Gerber file to Sierra to estimate
   the costs of an circuit board for the small-scale prototype made from
   HVPF instead of FR4.

Wire Frames

 - Brian has been thinking about an alternative design for the wire
   boards consisting of two 1/32-in thick G10 layers (one of which will
   be the STB and HVTB) and a Rohacell form core.  Tim was not worried
   about increasing flexing due to the wire load.  This design could
   serve to reduce the overall frame thickness by another factor of two.
 - Brian will make a full-scale mock-up to test the design.  Tim will
   do some wire-load distortion calculations for this design.

FDC CD-2 Document

 - David Lawrence worked to prepare the geometry files for our two
   design options (with and without cathode backing) based on files that
   Richard Jones had originally made.  David then passed these onto the
   folks at IU.  David has started some studies of momentum resolution
   We got some preliminary results for photon conversions from Mihajlo at
   IU.  The results were very confusing, and we became convinced that
   there is a bug somewhere along the way.  David and the IU folks are
   working on figuring things out.  
 - As the Monte Carlo studies will not be completed and checked on the
   time scale needed for CD-2 documentation, we agreed that we would
   write up what we have now.  Simon and DSC will complete the work on
   this document before Friday.

Magnetic Field Tests

 - Simon will talk to Bogdan in Hall A to get a commitment for
   their small silicon detectors as a backup plan.  Brian will contact
   BNL and FNAL to see what they may have available.  Brian will also
   talk to Elke to see if she has any suggestions for contacts in Germany.
 - DSC will talk to Stepan and Doug about how the magnet will be
   configured.  The magnet has been configured so that each of the six
   coils in each pole are driven in parallel.  However, in order to
   achieve the 1.4T field, the magnet would have to be configured in
   series.  The question then is whether the mini-torus power supply
   has a high enough current rating.

Cathode Frames

 - Brian talked to Paul Brindza about the use of carbon fiber in our
   cathode support frames.  He stated that this will not be an issue
   because the orientation of the frames is orthogonal to the field
   direction.  This limits severely the current that can flow in the
   carbon fiber, and the direction that the current would flow in is
   resistive in the material.

Cathode Backing

 - Brian reported that he has done some investigations of other foams
   and talked to Youri.  He cannot find any large bubble foam with a
   density lower than Rohacell.  He will continue looking.  We can
   also consider using a backing of Rohacell that is less than 5-mm


 - As Joe was at today's meeting, we took the opportunity to talk about
   the cabling of the FDCs.  The current plan is to use the 50-conductor
   cables for both anodes and cathodes.  Note, as the anodes only have
   34-pin readout, 16 conductors in the 50-conductor cable will not be
   used (but they will be configured with 34-pin connectors).  This was
   decided as the nominal choice as the 50-conductor cables actually have
   less copper in them than the 34-conductor cables.
 - As the cables will surround the entire detector, Joe will work to
   produce a drawing showing the cable packing.
 - Joe will contact the manufacturer about making cables with a thinner
   outer jacket to reduce material thickness.
 - As the signal cables can have jackets of any color we choose, Joe
   suggested we use different color cables for each FDC package to allow
   for easier identification in the cable trays and electronics.  This
   was viewed as a good idea.
 - Joe asked that we consider purchasing cables for him to study.  The
   minimum order is $10k.

Daughter Boards

 - We discussed the work needed to be able to readout the small-scale
   prototype with the ASIC preamps.  Fernando will need to complete a
   daughter board and a jumper to connect to the chamber.  Given that
   we would not be able to get very far in our studies without the
   FADCs from Gerard, we decided that the daughter boards and connectors
   for the small-scale prototype would not be needed until after the
   magnet tests this summer.  So, the right time frame is September.
 - Fernando stated that UPenn will most likely be responsible for 
   testing all preamps and that possible UAlberta might be testing the
   stuffed daughter boards.  More to come.

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.