Minutes 5-2-2007

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FDC Weekly Meeting

Date: May 2, 2007

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

Next Meeting: Wednesday, May 9, 2007 @ 1:30 p.m.

Cathode Prototyping

 - Brian has been in contact with the manufacturer of our dummy cathode
   boards about the few Ohm strip-to-strip resistance.  They believe that
   they did not etch for long enough.  They will probably ask us to
   send them back a sample of the problematic "boards" for checking.
 - Brian indicated that Brown and Sharp has indicated that they can
   perform the measurements of our no-backing cathode planes to measure
   the strip-to-strip separations (to look for distortions) as well as
   to measure the surface flatness.  Brian did not specify to them that
   we would prefer that these measurements are done with the cathodes
   sitting vertically (to eliminate gravitational sag).  He will follow
   up with the company.  If they cannot do the measurements in this
   position, we could fabricate a Rohacell disk to sit under the cathode
 - Brian will be away for most of May on travel.  DSC indicated that upon
   his return we need to work to consider the designs for the cathode
   backing to reduce the density of this support material with respect to
   the solid Rohacell piece.

Circuit Boards

 - We are still awaiting the results from Monte Carlo on the expected
   chamber rates with the new reduced material design.  This will allow
   us to specify the HV segmentation to enable Kim to complete the design
   for the HVTB boards.
 - We are planning on a design employing only 2 STBs and 2 HVTBs per
   wire frame.  Roger and Kim are awaiting word on where to put the
   daughter board connectors (and the connector type) so that they can
   complete the design of the STBs.  
 - Roger found a 4-kV rated capacitor that is the same height as the 3-kV
   caps that he had found before.  They are a bit wider, but this should
   not be an issue.
 - DSC asked Fernando to look into manufacturing a circuit board for
   the small-scale prototype from HVPF.  We would like to compare its
   properties to the standard FR-4 boards.
 - DSC asked Fernando to begin to consider a design of the preamp
   daughter board that will be compatible for use with the small-scale
   prototype.  We expect the first run of ASICs to be available for our
   testing in August.

New Prototype Cathodes

 - There was a hiccup in the order for the +/-75 deg cathodes for the
   small-scale prototype.  CCT marketing did not have the 2-micron thick
   copper material.  Brian and Roger will work out how to get the
   5-micron thick copper (on 1-mil kapton) completed while someone tries
   to get the 2-micron thick copper board material to CCT.  We should
   expect the first boards to arrive in July.

FDC CD-2 Document

 - Still waiting for input from Monte Carlo.  Richard Jones is working
   on the studies of the photon conversions in the inactive materials.
   Simon will follow up with him to find out the status of this work.  We
   need to know if our composite cathode frames are "good enough" or if
   we need to work harder to reduce the material thickness.  There is not
   much more that we can do except to replace the CH2 with carbon-fiber
   composites, but this is minimal.  Matt Shepard is working on the rate
   studies with the reduced material in the active portion of the chamber.
   We expect these studies to be completed in about a week.

Magnetic Field Tests

 - Plans continue to be fleshed out.  DSC and Simon have prepared a 
   test plan document and it is ready to be turned into Volker.  We
   are working on several fronts to be able to identify some detectors
   to be used external to the field to define a track through the FDC.
   We would like sufficient precision on this track measurement to
   determine the centroid shift along the wire.  Even without these
   external measurements, we should be able to quantify the effect of
   the field on the cathode resolution.

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/).  DSC is still
   waiting for feedback and comments from the group.

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