Minutes 12-13-2007

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FDC Weekly Meeting

Date: December 13, 2007

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

             (Curtis, Yves, Gerard for FDC/CDC portion)

Next Meeting: December 20, 2007

Manpower Update

 - DSC has talked to everyone matrixed into the FDC effort regarding
   work plans and time lines.  The time lines that have been established
   will be revisited in January 2008 and modified to take into account
   the delays in the project.

Composite Wire Frames

 - Brian has completed construction of 5 composite wire frames.  Two
   low density Rohacell core frames and one medium density Rohacell
   core frame will be selected for the phase 1 winding project.
 - Brian has indicated that he is satisfied that he has developed a
   construction procedure that will be amenable to mass production of
   these frames.  The alignment jig worked quite well and Brian has
   setting on employing Hysol epoxy for the construction.
 - The next step in the process is to deliver the frames to the JLab
   machine shop to add the o-ring grove on the back side and to add
   the through holes.  This work will begin in January and take about
   two weeks to complete.
 - The storage/transport container that should have arrived at JLab
   last week has not yet shown up.  Brian will look into this and
   make some calls.

Wire Stringing

 - Work continues from the folks at IUCF to finalize a statement of
   work and budget that they are happy with.  The first version of the
   SOW that they provided to me include language for Phase 1 only.  I
   have asked them to modify this to include all three phases.  Also
   the administrators have not fully accepted the budget that was
   prepared for the 3 work phases by the head of the wire chamber lab.
   They want to increase the contingency estimates as they are nervous
   about the current contingency levels (that DSC thought were quite
   reasonable).  The bottom line is that we don't quite know what to
   expect for a budget from IUCF.  However, it looks like we should
   receive it before the end of the year.  At that point the JLab
   procurement folks will take over.  They indicate that if things go
   smoothly, we should have a signed contract from both parties before
   the end of January 2008.

Composite Spacer

 - Yesterday we found out that Kim had not received the information on
   the spacer ring that goes between the face of the wire plane and
   the neighboring cathode frame.  Because she did not have this
   information, she had started to put components in the space occupied
   by the spacer ring.
 - The current design of the spacer ring is a composite annulus of
   I.D. 1022 mm and an O.D. of 1060 mm.  The I.D. is set to clear the
   solder pads and the O.D. is set to go just beyond the through holes.
   Tim will look into whether we can slightly decrease the O.D. or
   add cut-outs (scallops) between the through holes to give Kim more
   room to layout the STB boards.  Here real estate is a major issue
   in the space immediately between the daughter board connector and
   the outer edge of the spacer ring.
 - The spacer design includes an o-ring groove on each side to give
   a gas seal.  In the current design, these o-ring grooves lie
   directly on top of each other.  The depth of the groove goes through
   the G10 skin and into the Rohacell backing.  These rings will require
   special handling to be sure they don't fall apart.  However, he was
   fully convinced that they are structurally sound to handle the
   compression and to provide the light-weight spacer that is required.

O-ring Material

 - We had a discussion on the choice of o-ring material.  The two options
   are Viton or a silicone-based material.  DSC is worried about the
   use of any silicone-based material that can come in contact with the
   chamber gas volume.  This stuff is definitely chamber-unfriendly.  
 - One of the biases toward silicon-based o-rings is that they are
   believe to be softer than other materials.  Thus less force would be
   required to give a good gas seal.  However, during the discussion it
   became apparent that the Viton o-rings come in different types, some
   of which are quite soft and should do the job for the FDC.


 - Kim had a bit of a set back with the issue of the space required for
   the spacer (see above).  This is a relatively minor issue for the
   HVTB boards, but is still an issue on the STBs.  Is there enough
   real estate to lay out the traces and the required components.  
 - The plan for wire frame stuffing is to do as much of this as possible
   before the wire winding.  This is viewed as important to minimize
   handling of the wound frames.  Also, the large-scale stuffing will have
   to be done by an outside company, and it makes no sense to send out
   frames with wires on them.  This is asking for trouble.  After the
   winding is complete, there will be a few remaining components to solder
   onto the boards, and that will be here at JLab.
 - Kim has nearly completed the design of the HVTB boards.  She has a
   few issues with some resistors not being placed between the solder
   pads.  There are some other relatively minor technical changes requested
   by DSC and Fernando, but these boards are converging nicely.
 - It was agreed by all that the positions of the daughter board connectors
   on the STBs can be viewed as final.  Kim can now start the detailed
   work of laying out the traces from the HV-blocking caps to the
   daughter board connectors.  The power and ground layout has been
   extensively discussed and we are converging on a good design in this
 - As the circuit boards will not be done this year, we will seek to
   continue having Kim work on these boards at the 50% level for January
   2008.  This will allow her time to complete this work and oversee
   the procurement of the boards for the prototype.

Cathode Boards

 - The positions of the daughter board connectors are not yet final on
   the cathodes.  They were recently repositioned to be compatible with
   the cooling system developed by Bill.  However, he forgot to take
   into consideration the fact that the cathode board is a three-piece
   design.  Bill and Chuck will look into the problems and report back
   to the group on the issues and what can be done about them.

Upcoming Work

 - Brian will start work next week on the construction of our first
   composite cathode sandwich.  So far, only sandwiches made with solid
   G10 rings have been attempted.
 - Brian will mount the +/-75 deg cathodes for the small-scale FDC
   prototype on the associated frames in the first part of January.
 - Simon will give an update next week on his analysis of the B-field
   test data to let us know where we stand and what is left to do.
 - We discussed the offer of additional help for the FDC system from
   the accelerator group and could not come up with anything at the
   current time.


 - The folks responsible for the individual design aspects for the FDC
   should provide a complete set of design drawings (even if they are
   preliminary to DSC).  We need to understand where we are at in the
   design and what areas we have not covered.

Cathode Board Readout

 - Roger has completed his design plans for the scheme to connect the
   cathodes to the daughter board connectors.  The solution is a
   simple circuit board that the daughter board connector is mounted to.
   This circuit board includes a few resistors for addressing the
   daughter board card.  The flex cable will attach to this board and
   be soldered to the cathode.  The circuit board that Roger has
   designed will attach to the back of the G10 skin that supports the
 - At the present time, he has submitted his circuit board design for
   quotation.  He expects to complete procurement before the end of the
   year.  The plan is to put together a mechanical prototype of this
   connection scheme to see how and if it will work for the FDC.

Other Updates

 - The next FDC Monte Carlo meeting will take place tomorrow.  Progress
   reports will be made on the continuing development of the track
   finding and fitting algorithms and the issues with modeling the
   chamber response in the magnetic field.

Combined FDC/CDC Discussion

 - We discussed the current status of the ASIC/daughter board tests that
   are ongoing at CMU.  So far the output of the amplifier board is
   totally dominated by noise.  The CMU folks are working on this to
   track down the source/s.  The FDC group will install their daughter
   boards on the small-scale prototype early next week if all goes
   according to plan.  As it is crucial to get this all working,
   Fernando and Gerard will be very hands on, both at JLab with the
   FDC and at CMU with the CDC.  Mitch will need our feedback on the
   ASICS by no later than March 1, 2008.  Fernando will circulate a document
   on what tests need to be performed for feedback to Mitch.  This
   document will be circulated in the next few days.  Note that at the
   current time, Mitch is working to understand why the measured power
   dissipation of the ASICS is larger than what he had simulated.
 - Curtis indicated that we will need to complete another version of
   the Hall D design report in time for the March chamber review.
 - We reviewed the plans for the FDC cooling system designed by Bill.
   CMU would like to employ a forced-air cooling system.  Bill and
   Fernando will be doing some thermal tests with the daughter boards
   to give feedback to this plan as well as the FDC cooling design load.
 - We discussed briefly the plans for the LV and HV systems and the
   associated grounding requirements.  Fernando is thinking about this
   at the current time.  DSC will be meeting with Joe Beaufait soon to
   start work on the design of these systems.
 - We discussed chamber installation and alignment systems briefly.
   Neither the FDC nor CDC folks have thought too hard on the details
   and specifics of either topic.  However, both groups do have some
   documented descriptions of how things should be installed and
   aligned in general.  Over the next several months, we will work to
   flesh these ideas out.
 - We discussed monitoring and time histories.  Both groups will first
   need to prepare a list of what they would like included in the
   monitoring and time histories.  We can then approach the Hall D
   slow controls group (O.K., ...,  Elliott) about our ideas.

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.