Minutes-10-29-2009

FDC Weekly Meeting

Date: October 29, 2009

Participants: Daniel, Beni, Simon, Fernando, Mark I., Stephen, Eugene

Next Meeting: November 5, 2009 @ 1:30 a.m.

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General Construction Updates

 - The single layer prototype assembly was completed and was studied in
   a 90/10 Ar/CO2 environment. Initially the chamber was laying in a 
   horizontal position. We were expecting the chamber to plateau with a 
   S-F voltage difference of 2000 to 2100 V. 
      - The chamber was grounded in its nominal configuration using a 
        series of temporary cathode grounding boards provided by Fernando.
      - We could not get above 1300 to 1800 V without sparking and large 
        current draws. 
      - We were concerned about gravitational sags of the cathodes, so we 
        rotated the chamber to its nominal vertical orientation and rechecked.
        No changes were seen.
      - The chamber was opened up and tests of the wire frame with attached 
        cathode were performed. We found two design problems of field bus
        vias arcing to sense solder pads. We potted with Hysol epoxy and
        were able to get the associated busses close to nominal voltage
        before the next problem revealed itself.
      - At still higher voltages we found HV breakdown between the sense
        wire HV resistors and the field wire solder pads. Recall that the
        resistors were mounted in Phase 1 stuffing before winding and were
        placed between the solder pads. Some are clearly too close. They were
        potted using Hysol epoxy. Gas is now flowing and HV checking will
        start later today.
      - We plan this week to start looking at signals from the wires and
        cathodes of the single layer configuration. If we don't get to it
        this week, this will certainly happen early next week. Stay tuned for 
        news and developments. We would also like to look for HV breakdown
        and current draw problems with the 40/60 Ar-CO2 mixture before
        continuing on stack construction.
      - Fernando will add the problems discovered to the work list for Kim.
 - Single layer studies will continue for about a week before we return to
   stack construction. More news coming soon.
 - The preliminary FDC stack assembly document draft is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. The document will be
   fleshed out during the assembly procedure for the full-scale prototype.

Wire Frame Update

 - Wire frame P1 is now under test in the single layer prototype.
 - Wire frame P4 has undergone a preliminary electrical QA check and has
   a few problems that need to be addressed.  Wire frame P3 will then follow.
 - We need to have a dedicated meeting to design what the schedule for
   work on the Phase 3 wire winding will be. The highest priority for
   work scheduling will be doing work on upgrades of the wire winding
   facility. This includes a better strongback design, the design and
   construction of precision combs, modification to the wire winding
   table, and a list of other items with the system. Stay tuned, more
   to come.
 - The wire frame construction document is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. We will include
   the information on the wire electroplating process shortly.
 - The parts of the jig to use for the wire electroplating operation
   are in our hands. They will be assembled as we find time.

Cathode Update

 - Progress updates:
     * All rigid-flex assemblies have gone through QA and been delivered
       for attachment to our cathodes.
     * Roger got the new rigid-flex order of a couple dozen pieces and has
       turned them over for soldering and then testing. They will be ready
       for us when we are ready for them.
     * Casey has been working on soldering rigid-flex assemblies to the
       first of our two cathode sandwiches. The soldering on one cathode
       is complete (electrical checks still to be done) and he has completed
       about half the soldering on the mated cathode. The soldering work
       will be completed on this cathode when we are done with the single
       layer checks.
 - The current draft of the cathode construction document is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS.
 - Roger needs to prepare a document for QA/stuffing/cleaning for the
   cathode boards and a similar document for the cathode daughter
   boards and ground boards.

ASIC Preamplifiers

 - Fernando has certified the lastest ASIC preamplifiers as meeting our
   design specifications. See GlueX-doc-1364 (The Gas-II/GPC-II GlueX
   Preamp Card Preliminary Test Results) for details and results. Fernando
   has one anode board and one cathode board available for the single layer 
   tests.

Design Discussion

 - Bill raised an intriguing idea for simplified the rigid-flex and cathode
   design. We agreed it might be something that will simplify the design,
   reduce costs, and make the soldering work easier. As there were some
   issue to hash out, we decided to take this offline and continue the
   discussions. The basic idea Bill had was to fold the cathode board
   through the slot on the frame and to solder the flex assembly to it on
   the back side. This would eliminate cutting pockets into the back of the
   wire frame and allow us to increase the trace spacing on the cathode for
   soldering to the rigid-flex assembly. More to come.

Cosmic Ray Test Stand

 - Beni has been investigating the wiggles seen in the reconstructed wire
   position from the cathodes. We focussed on log entry 419 in the
   FDC logbook. We believe that the periodicity seen is due to the algorithm
   Beni is using to determine the U and V centroids. He will talk to Simon
   and get his parametric form to see if this addresses the problems. No new
   news as of yet. Stay tuned.

Work List

 - The FDC short-term work list has been posted on the FDC web site.  
   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.