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FDC Weekly Meeting

Date: November 5, 2009

Participants: Daniel, Mark S., Beni, Bill, Casey, Simon, Fernando, Mark I., Eugene, Glenn

Next Meeting: November 12, 2009 @ 1:30 a.m.

General Construction Updates

 - Fernando provided one of his new preamp boards and we found that in
   the 90/10 Ar/C02 mixture we were efficient at dV=1800V instead of the
   2000V we had been expecting. We saw beautiful signals with very good
   signal to noise background! We also used the anode board to look at
   cathode signals and, even though the gain is 5x smaller than the final
   cathode preamp boards, we saw lovely signals as well from the cathodes.
   News most awesome! See the FDC webpage for some lovely pictures. 
 - We moved to a 40/60 Ar/CO2 mixture (the nominal gas mixture) and were
   expecting to be efficient at dV=3000V. We could not get the chamber
   above dV=2500V without large current draw but we saw no signals. The
   spacer ring was found not to provide an adequate gas seal. We improved
   things a bit and were final able to see good signals at dV=2500V with
   reasonably low current. We were plagued by high oxygen content in the
   chamber gas.
 - Fernando now has ready a cathode preamp board (with the new GAS-II ASICS) 
   and we have a test program in place on the single layer prototype, but we 
   are working to improve the gas seal. We expect to be able to turn things
   over to Fernando tomorrow afternoon for him to begin his battery of tests.
 - Bill has been working with the gang to improve the spacer gas seal. One
   problem is that the spacer goes across traces that stick up about 3 mils!
   He is working to overcome the problem and give us a robust and reliable
   gas seal. Another issue is that the gaps between the wire frame circuit
   boards were not fully filled in, introducing leaks under the gas spacer
   ring. He also found leaks about the rigid-flex assemblies on the cathode
   frame that was laminated to the wire frame.
 - Once the gas seal issues are properly and satisfactorily dealt with, we
   will fill the chamber with the nominal gas mixture and Fernando will need
   several days to study the chamber response with the preamp boards. When he
   is done, we will return to stack construction (and maybe leak reduction).
 - 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.
 - The fact that we seem to be efficient at dV values below expectations
   from the small-scale prototype (same gas and same cell size) has led us
   to speculate that the wire size must be different in the two chambers,
   and most likely it is the sense wire. The full-scale chamber planes were
   strung with 20 micron diameter sense wire and 80 micron diameter field
   wire. If the small-scale prototype were strung with 25 or 30 micron
   diameter sense wire, this would explain the dV discrepancies. We are
   looking into measurements of wire samples from the small-scale prototype.
 - The full production wire order for the FDC and CDC has arrived and we
   are moving to get the SEM work completed to qualify the wire. More to
   come. Mark will take the lead in contacting the W&M SEM folks to set up
   the work.
 - We will have to add steps in our construction plans for leak checking.

Wire Frame Update

 - Wire frame P4 has undergone a preliminary electrical QA check and has
   a few problems that need to be addressed with the connectors and 2
   capacitors need to be replaced. We then need to pot the regions that
   led to HV breakdown problems on frame P1. 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.
 - We need to prepare a document for the electrical QA of the preamp
   connectors on the wire boards.
 - DSC, Bill, and Fernando will plan a meeting to go over the circuit
   board design work for Kim.
 - Peter Monaghan gave us some contacts for a board house that can make
   large scale boards and a potential supplier. DSC will give Kim the
   contact information and let her find out if there is any hope of 
   getting larger size boards.

Cathode Update

 - Progress updates:
     * Fernando has delivered the new batch of rigid-flex assemblies after
       all soldering work was completed. These boards need to undergo a
       battery of electrical QA checks.
     * Casey has been working on soldering rigid-flex assemblies to the
       second of our two cathode sandwiches. Soldering work on the first
       sandwich has been completed and electrical QA checks are in progress.
     * Even though we are nearly done with the soldering of the rigid-flex
       assemblies, we will order another stencil and use it for testing of
       soldering procedures.
 - The current draft of the cathode construction document is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS.
 - We need to prepare a document for QA/stuffing/cleaning for the cathode 
   boards and a similar document for the cathode daughter boards and ground 

Preamplifier Boards

 - An order for more ASIC chips is expected very shortly. Fernando expects
   that we will have ~40 boards ready by the end of November.

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

 - Several meetings ago we focussed on the wiggles seen in the reconstructed 
   wire position from the cathodes (see 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. Beni has not gotten 
   back to study this. 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.