Minutes 11-29-2007

FDC Weekly Meeting

Date: November 29, 2007

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

Next Meeting: December 6, 2007

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Manpower Update

 - Everyone matrixed into our working on the FDC hardware aspects
   excluding Tim and Chuck have been provided with a detailed list
   of tasks and an associated time line for work until the end of
   June 2008.  This is our internal deadline for completion of the
   construction of the full-scale FDC prototype.
 - DSC would like everyone in the group who has not already talked
   to him to schedule a brief meeting with him to go over the 
   schedule to be sure we have an agreement on the list of tasks
   and the schedule.  Please do this in the next few working days.

Formality of Change Requests

 - As we are working toward a rather tight deadline to construct the
   FDC prototype chamber and to complete the system design, we need
   to have a bit more formality regarding changes in the base design.
   The issue of course is that the individual sub-projects for the FDC
   are highly coupled.  A change by one person (even a seemingly minor
   one) may have unintended implications for the work that someone else
   is doing.
 - The first question that came up in this regard is "What is our
   base design".  Chuck will review the drawings that he has and we
   will see if all of our nominal design choices are captured in his
   drawings.  He will present some drawings at our next meeting.
 - The approach will be that any changes to the design will be
   advertised in advance of the weekly FDC meeting, then we will go
   over the requests in detail at the next scheduled meeting.  We will
   either approve the change or not.

Composite Wire Frames

 - Two of the composite wire frames have been completed.  One has a
   medium density Rohacell core and the other a low density Rohacell
   core.  The third frame is in progress and will be done on Monday.
   Within two weeks, all 5 frames will be completed.  Three of these
   will be sent to the wire winding facility.
 - The construction of the wire frames has relied on our new alignment
   jig.  This system works beautifully and does not seem to need any
   additional tweaks in design for now.
 - The wire frame storage box has not arrived yet, but is due into JLab
   any day now.
 - Brian has been asked to clearly label each chamber frame and make
   a clear logbook entry on the construction techniques with each frame.
   We need to be able to tell which frame is which.  The same will be
   true for all of the frames that we construct, wire frames and
   cathode frames.

Wire Stringing

 - We are presently awaiting the official budget from IUCF on the
   wire stringing project.  This should be any time now.
 - DSC and Elke have been in contact with the JLab procurement folks.
   Due to the fact that we can have a DOE facility bidding against
   a university, we will not open this project up for bid as our two
   sources are FNAL and IU.
 - We will simply look at the two budget and make a decision based on
   which is the cheapest and complete the wire winding contract.  
 - As things stand now, the paperwork on the JLab side is coming along
   and the final award of a contract should follow relatively quickly
   once all budgets are in hand.
 - We will keep folks up to date as there is news on this front.
 - No work yet on the strongbacks, but this work will be completed on
   the time scale of 2 weeks or so.

STB/HVTB Design

 - Kim has been continuing work on the circuit board layouts for the
   wire frames.  The outline of all six PCBs is complete and she has
   been laying out the power and ground for the STBs.  This work is
   nearly done.  She is ready to layout the traces from the HV isolating
   capacitors to the daughter board connectors.
 - Issues have come up with the final placement of the wire frame
   daughter board connectors due to issues of connecting the preamp
   board cooling brackets with the cooling lines.  More on this issue
   is included in the cooling discussion below.
 - The connector placement issues will cause Kim to put the STB trace
   layout on standby until things are finalized.  In the mean time, she
   will begin work on laying out the HVTB boards.
 - The issue of additional holes in the STB and HVTB boards was discussed.
   Presently we have 24 through holes for stack assembly.  However, the
   need for additional holes for strain relief of the cooling system came
   up.  We have decided not to include these holes in the circuit boards,
   but instead they will be included in the G10 backing skin on the wire
   frame.
 - We still have not converged on a final design for connecting high
   voltage to the HVTB boards.  Both Fernando and Simon are investigating
   the available connectors.  If they are too large, they cannot go on
   the HVTB.  The design might then have to rely on pigtails soldered
   to the HVTB that extend back to a distribution board on the downstream
   face of each package.  Discussions on this front will start to get
   serious over the next two weeks.

Cooling Scheme

 - Bill reviewed the current status of the design for the FDC electronics
   cooling system.  The design is rather complicated due to the need to
   minimize mass, allow for connectivity to each of the 130+ cards per
   package, all while trying to meet the cooling system load requirements.
   This has lead Bill to move around the daughter board connectors on both
   the cathodes and wire frames.  
 - Of course there is a conflict between the work Bill is doing and the
   work Kim is doing.  She needs the positions of the STB connectors fixed
   to lay out the traces, but the present locations that Kim is using may
   not allow for connectivity to the cooling system as it is currently
   designed.
 - The cooling system and connectivity plans to the daughter boards cards
   looks rather cumbersome, with potential issues of accessibility of the
   daughter boards and other servicing requirements that are essential.  
   We discussed a number of issues for Bill to consider as he moves forward.
   Certainly we should use aluminum instead of copper wherever we can get 
   away with it to reduce mass.  We all agree now that Fluorinert coolant 
   is quite superior to water in this design.  We also considered a hybrid 
   system of brackets on some of the daughter board cards to connect to the 
   cooling lines, and flexible straps on other daughter board cards.  More 
   thought on tweaking the design will be required to make the system work 
   and still meet the physics (and budget) requirements.

Cathode Board Readout

 - Roger has nearly finished his design for a system to connect the
   cathode boards to the daughter boards.  He has gotten a number of
   price quotes that seem fairly reasonable.  He still needs to include
   resistors for addressing lines for each card (he will use the same
   system design as Kim is using for the STBs).  Once this is finalized,
   he will place an order for construction of a prototype.  The design
   will use a short flex cable that is soldered onto the cathode.  This
   flex cable will feed through a slot in the cathode support frame that
   attaches to a backing PCB onto which the daughter board connector is
   mounted.  This backing PCB mounts on the back side of the G10 skin
   that the cathode is mounted to.
 - Roger will produce a side view drawing of his assembly so that we
   can understand how much space is required between the G10 skins of
   the cathode sandwich.
 - Roger plans on placing the order for the prototype parts before the
   end of the year.

Cathode Layout

 - Roger has a design for the cathodes that runs the strips up to the
   individual daughter board connectors.  Again, there are 9 daughter
   board connectors on each cathode board (eight on top, one on the
   bottom).  This design will be updated once the daughter board
   connector placement is finalized.
 - The issue of how to actually construct the cathodes was discussed
   again.  The nominal design choice is to back each 3 piece cathode
   design with a 2-mm thick layer of low density Rohacell.  The main
   issue with construction is how to guarantee the relative alignment
   of each of the pieces of the cathode.  This is still not worked out
   in detail.  Once the five composite wire frames are constructed,
   Brian will work to construct a composite cathode.  We have not
   constructed one of these as of yet.
 - The issue of how to survey the flatness of the cathodes came up
   again.  At the present time, we do not have a scheme in place for
   flatness measurements.  The JLab Survey Group has not closed the
   loop on doing something, and we have not pushed them lately.  Brian
   will talk with George Biallas to see if he has any contacts that
   might be able to help us on this matter.
 - To support the cooling system, we will want to include some holes
   in the cathode frames near the outer edge.  Bill and Chuck will
   interact with Roger to finalize the number and placement of these
   connection points.

Magnetic Field Tests

 - Simon just got back to town after a week or so in Germany.  He
   still is working on the data analysis.  A more detailed report will
   be given as to where he is at our next meeting.

Daughter Board Testing

 - Fernando has the daughter boards and interposed boards done and
   they are undergoing tests on his bench.  We can take possession
   of them next week (3 cathode boards and 1 anode board).
 - We have been working to re-setup our cosmic ray test stand in the
   Test Lab.  A lot of progress has been made and Simon is working on
   getting DAQ up and working.  He hopes that by the end of this week,
   he will be able to take data.  We will re-establish chamber operation
   with the Hall B SIP preamplifiers before we make the change over to
   the ASIC boards.  We have also constructed two 18-m long signal cables 
   of the type that we are envisioning for the final system (Spectrastrip
   cables).  These will be used during the tests to make sure that the
   appropriate capacitance is modeled. 
 - We test plan for what we need to provide to Mitch and Gerard is being
   developed.  Gerard needs the input on the preamplifier performance for
   his design of the FADC front end circuitry (shaping) and obviously
   Mitch needs the information for the next revision of the ASIC chips.
   In this regard, Gerard and Simon will be traveling to CMU in about
   two weeks to work on the shaper design.  The decision was made to
   work with the CDC system as this system has the most severe requirements
   for shaping to get the required time resolution from the FADC data.
   The lessons learned will allow Gerard to finalize a design that works
   for both the CDC and FDC.  Gerard may also travel to JLab to work
   with Simon on the FDC in December or January as needed.

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.
 - The FDC meeting on Dec. 13 will be a combined FDC/CDC meeting.  We
   will have an FDC-only meeting from 1:30 to 2:15 p.m. and then the
   CDC folks will join us.  The issues to be discussed are electronics
   and cooling.  We will circulate an agenda as we get closer to the
   meeting so that we identify the relevant folks that need to be
   present for the whole meeting (but of course everyone is welcome to
   stay).
 - We have new lab space that has been made available in the F-wing of
   CEBAF Center.  We need to decide how we can use this space as well
   as our space in the EEL building.
 - Brian will talk to Jack Segal about the FDC system taking up
   residency in the EEL building clean room tent.  We need occupancy
   in April for prototype construction.
 - DSC will not be available for next week's FDC meeting.  Simon will
   step up and organize the meeting and prepare the minutes.
 - The accelerator group has offered manpower to the FDC project.  These
   folks have both electrical and mechanical experience.  If there is
   a mission critical need for special project manpower for the FDC, talk 
   to DSC and Elke and we can discuss it.  The trouble is that Elke has
   no more money to spend.

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.