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FDC Weekly Meeting

Date: February 18, 2010

Participants: Daniel, Simon, Beni, Lubomir, Mark S., Bill, Roger, Fernando, Glenn

Next Meeting: February 25, 2010

Construction Space

 - Today Tim and Glenn toured EEL 126 to discuss the space issues for
   FDC construction. Glenn reviewed the situation and our needs. He has
   asked us to prepare two floor plan drawings for EEL 126. The first with
   an additional 10 ft added to our space out toward the door. The second
   all the way the wall by the stairs. He also asked us to provide details
   on when the space must be in our possession.

General Construction Updates

 - The two-layer prototype continues under source tests in the cosmic ray
   test facility. When we want to open this up to investigate the several 
   HV bus problems and to consider adding the third layer remains to be
   determined. We probably will aim to do this before the middle of March
   to give DSC time to work on the detector before he disappears.
 - Casey and Mark have continued to work on sealing the 24 through-holes 
   in our third prototype layer with epoxy. This work is nearly done and
   then we will prepare a bench test to check the system out. Bill is
   worried about leaks problems through the alledged hole in the ground
   plane between the cathodes being exaserabated by Venturi effects near
   the gas inlet and outlet. We will plug these holes for the test. Stay
 - Brian checked on how the oxygen sensor was tested. It turns out that
   it was not tested properly. After rechecking, it seems to actually be
   in fairly reasonable shape. Connected to a nitrogen bottle, it read
   about 20 ppm of oxygen. The issue with this sensor is that it contains
   a high impedance sample cell, so it can't be used in series with our
   gas line. We need to divert a bit of flow. Brian is concerned that with
   the low pressures that we have on our input and output lines, we may not
   even get a meaningful oxygen measure at all. He suggests we give it a
 - The preliminary FDC stack assembly document draft is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. We will review this
   document in the coming weeks to update out-of-date or old procedures.
 - Fernando will order a few more aluminum pieces for the preamp cards that
   he is prepared as we will be about a dozen or so short.

Frame Modification Studies

 - The two laminates for the cathode boards (G10 skin + new inner G10 core)
   were put together and sent to the machine shop to be fly cut to the
   final thickness. These pieces are expected back this week for attaching
   the last G10 skin to. These boards will then be ready to attach to the
   tensioned dummy cathodes.
 - One dummy cathode board from Kapton is ready for tensioning. The material
   for the second has arrived and will be put together on the tensioning
   frame in the next several days.
 - Bill has put together a few slides showing the frame design changes.
 - The redesigned frame piece for the wire board is not expected back from
   the shop for another couple of weeks.

Wire Frame Update

 - The wire frame construction document is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS.
 - Kim has gotten quotes for the wire frame PCBs made from a reduced
   number of boards. A single piece PCB is out of our price range. She then
   got quotes for an annulus made up of 4 boards (one STB,one HVTB, two 
   filler boards). The total is about $120k without including board stuffing.
   We do not yet even have a company lined up that can potentially handle
   boards this size. We will continue to pursue this option, but time and
   costs are getting in the way.
 - Kim expects to be done with her work on the PCB redesign by the end
   of next week and will then circulate the boards for review. The questions
   regarding glue strip positioning relative to the solder pads and the
   location/style of the wire sighting fiducials passed to Keith Solberg
   at IUCF have not gotten a response. DSC contacted Keith earlier this
   week to give him a reminder. We want to start the procurement process for
   the circuit boards by the end of March.

Cathode Update

 - The current draft of the cathode construction document is located at:
   /u/group/halld/Engineering/PRELIMINARY DOCUMENTS.
 - Casey has prepared a document for QA/stuffing/cleaning for the cathode 
   daughter boards. You can read this document as it stands now.
 - In order to officially accept the cathode board material, we have asked
   for the company to provide a sample piece for us to test. The sample has
   arrived at JLab and DSC did some inspection and measurements. All looks
   good. Fernando will take a final look before we sign off on the material.
   When we are ready, we will notify Roger and he will complete the 
   notifications to the relevant JLab and company reps.
 - The next rigid-flex design meeting will take place later this month.
 - We would like to push to get the cathode board procurement done by the
   end of March.
 - David Lawrence is working to give us input on the hole size in the
   cathode center. Stay tuned.

Prototype Testing

 - The current version of the full-scale prototype test plan is on the
   GlueX portal as (GlueX-doc-1304).
 - To connect the full-scale prototype to the readout electronics, Fernando
   is designing a simple translator board that allows connection from the
   24-channel preamp connector to the 16-channel connectors on the ADCs and
   TDCs. These boards should be ready by the end of this month.
 - The signal cables for the full-scale prototype are being made up by
   Fernando's group and should be ready shortly.
 - The two-layer prototype has been under tests for several weeks. Beni has 
   been measuring plateau curves and studying drift time spectra. His most
   recent studies are in the FDC Log Book (see entries 423 to 427). He 
   studied the plateau and drift time distributions for a long wire at positions 
   of 21 cm, 7 cm, 2.5 cm, and 1 cm from the edge of the frame. He will also move 
   to repeat these studies with a short wire.
 - Beni has been battling some HV/current problems in the two layers of the
   FDC prototype. He tried reverse biasing the chamber. This seemed like it
   led to some improvement in the currents and biasing behaviors, but it is
   not clear if it was a long-term effect. Some of these mysteries will have
   to wait until the chamber is opened up again. Beni will probably have to
   mount his source/trigger scintillator on the other side of the chamber to
   finish his work due to the number of problematic busses on the chamber side
   he has been studying.
 - Beni has recently changed the gas mixture from 40/60 Ar/CO2 to
   60/40 Ar/CO2 to study the effect of the chamber performance on the gas
   mixture. Results coming soon.
 - Beni will be including the cathode preamp card and hooking it up to
   ADC readout shortly.
 - Fernando will pursue purchasing enough cathode ground boards for all
   six cathode planes for the full-scale prototype.
 - A while 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. Stay tuned.

Construction Updates

 - No new updates on the wire inspection this week.
 - DSC has contacted Keith Solberg at IUCF regarding the status of the
   review of the Phase 3 budget for the wire winding. Keith indicated that
   this work is in progress and should be done shortly.
 - It is time for the next Phase 3 preparation meeting with Keith Solberg,
   Bill, and DSC. DSC will work to schedule this only after we have a
   preliminary Phase 3 budget in our hands. See the work plan at: 
   Phase 3 Preparation Work
 - Master list on wire and cathode frame redesign work is located at:
   Frame Modification Work.
 - Bill continues working on a brief write-up of the summer IUCF work. When
   it is completed, we will circulate it for discussion with Tim and others.
   It will then be sent on to IUCF for budget estimates.

Mechanical Prototype

 - DSC prepared a brief write-up regarding the FDC full-scale mechanical
   prototype. It was circulated around to a small group of folks. We will
   do a bit of work to beef this up and then post it for group comment.

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.