Minutes 1-24-2008

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FDC Weekly Meeting

Date: January 24, 2008

Participants: Daniel, Brian, Simon, Roger, Chuck, Fernando, Bill, Elke, Denny

Next Meeting: January 31, 2008 @ 1:30 p.m.

Composite Wire Frames

 - Two of the three composite wire frames needed for our test winding
   have been completed in the JLab machine shop.  With the third frame,
   there were some minor problems with the epoxy layer for the o-ring
   group that required some additional machining time.  The last thing
   to do is to machine the through-holes and the full complement of
   frames will be done and ready for winding.

Wire Winding

 - Allison has promised to look at the purchase request for the test
   wind and hopefully she will move to sign the paperwork soon.  More
   details to come when we have word on progress or delay.

Composite Cathode Construction

 - Brian and Denny are now starting work on construction of the first
   composite cathode.  They are gathering all of the necessary parts
   and pieces to begin assembly.  The big aluminum jig plate that is
   being used to machine the through-holes for the wire frames is 
   needed before epoxy is applied to the G10 skins.  Construction
   should begin tomorrow.
 - Brian estimates that it will take about two days to complete
 - Brian will spend some time finalizing the layout of the ground plane
   that goes between the cathode planes in the sandwich.  This cathode
   needs to have tabs that stick out and are accessible to make 
   connections to the external chamber ground.
 - We had some discussion about the latest design modification to make
   each FDC package a single gas volume.  The issues are how to make
   holes in the cathodes and ground planes.  Both are very thin and
   we believe that pre-cutting the boards before installation will not
   work.  The cathode holes, which could be located in the center
   region where the strips are removed and at the outside edges where
   there are no strips, could be laser cut after the 2-mm thick foam
   backing is attached.  This will need some testing.  The ground
   planes may be more tricky as they are only 6-microns thick.  Brian
   will think about options and come up with some drawings.  It may
   be that we could put the gas through-holes for the ground plane in
   the support frame.  Bill will talk to Tim about what tools we have
   for impedance calculations.  Whatever options we choose, we want
   to ensure that we have good gas flow throughout the entire FDC

Small-Scale Prototype

 - Brian plans on mounting the +/-75 deg cathodes to their frames for
   the small-scale prototype next week.  Keep in mind that these are
   the first boards that we have with 2-micron thick copper.  All other
   boards have 5-micron copper strips.  These boards will be installed
   into the prototype shortly.
 - Simon and Fernando have prepared a pulse library for Gerard and Mitch
   from the readout of the prototype with the ASIC preamplifiers.  Due
   to the very large gain, they have attempted to prevent saturation by
   reducing the HV on the chamber (probably below the plateau knee). 
   These data (8 channels of anode and 8 channels of cathode) were taken
   with the 18-m long Amphenol Spectra-strip cables on the readout.
 - The data with the ASICs was taken without the proper setup for
   Gerard's shaper boards.  Gerard will send a list of necessary component
   modifications to Fernando who will make updates to the board.  We
   will have a meeting with the FDC and CDC folks, along with Mitch to
   discuss the results of the work in the next several weeks.
 - Fernando measured the cross-talk on the Amphenol readout cables to
   be less than 1% -- good news.
 - Simon will soon take a long cosmic ray run with the ASIC readout to
   check resolutions and to compare with the prototype readout with the
   Hall B SIP amplifiers.  He will need to perform a gain calibration
   run.  This measure of channel-to-channel gain variations for the ASICs
   will be nice to compare to the bench measurements that have been made.

B-Field Test Data

 - Due to the low statistics and problems with the multiple scattering
   (and hence track definition), it is not clear if we will every get
   convincing results from the test run.  We had hoped to be able to
   see the Lorentz shift along the wire compared B on data with B off
   data.  However, given the multiple scattering through the magnet
   pole, we cannot easily pick out which side of the wire (in the
   small-scale prototype) the event passed.  The issue is that the sign
   of the Lorentz effect, and hence the shift direction, depends on which
   side of the wire the event passed on.  It may be that we will be
   able to pick out a width change that can be compared to a model.
 - Note that the current analysis of the B-field data shows a narrow peak
   in the difference between the external tracking chambers and the
   small-scale prototype (which is what we are looking for), but it also
   shows a sizeable non-symmetric background (that we do not understand).
   Simon will continue with the data analysis and continue thinking about
   this analysis, but we agree that this work is not as high a priority
   as other things that he is working on.


 - Fernando has completed his review of the STB and HVTB design and passed
   his comments on to Kim.  He had some issues with the labeling of the
   signal lines and there were a few places where traces on neighboring
   boards cross each other on adjacent layers.  Kim will work to make
   changes to the boards.  She probably has 2 to 3 days of work to complete
   the boards.  Kim has already started the paperwork to begin procurement
   as soon as the board design is finished.  She will also order the
   necessary components and connectors at the same time.

Cathode Daughter Boards

 - Based on the feedback and discussion from our last meeting, Roger
   has updated the cathode daughter board to include the ERNI connector
   and the addressing resistors.  Roger will look to the nominal
   geometry defintions for the cathode frame to be sure that there is
   room for the now wider cathode daughter boards given the locations of
   all of the boards and the locations of the through-holes.

Cooling System

 - Bill has continued to investigate our options for a chiller system for
   cooling the FDC preamp boards.  He believes our best option will be
   to construct our own system that employs the LCW in the Hall.  He
   will prepare a block diagram of his ideas and circulate for comment.

LV/HV System Design

 - DSC and Fernando will meet with Joe next week to follow up on his
   planning of the FDC LV and HV systems.  Fernando has prepared a
   low-voltage block diagram that he will pass onto Joe.  He has already
   prepared a similar document for the HV (GlueX-doc-927) that has been
   posted on the portal.
 - For the LV system, Fernando is planning on a distribution box just
   outside the solenoid.  The LV lines from the chambers will be cables
   compatible with the ERNI connectors.  They carry both power and
   signals (for addressing and temperature readout).  In the distribution
   box, the signals for the addressing and readout will be split from
   the power lines.  
 - Fernando still has not made a decision on whether we will employ a 
   CAEN or a Weiner LV system.  Both are possibilities. It is clear that
   with these power supplies, we will not need a fuse system.
 - In his layout he has a single cable for each cathode daughter board
   and will have two cables for each wire plane (one for each STB).


 - DSC has collected all of the available FDC subsystem design drawings
   and placed them on the FDC website.  The URL is:
   http://www.jlab.org/Hall-D/detector/fdc/drawings.html.  Folks should
   go through the drawings and let DSC know what drawings and/or categories
   are missing for a complete design set.

FDC Mini-Review

 - The FDC mini-review on technology choice is scheduled for Feb. 1.
   The reviewers will be Howard Fenker (JLab) and Larry Weinstein (ODU).
   DSC has prepared a new version of the FDC Technical Design Report
   to reflect the current system design.  This will be provided as part
   of the pre-briefing material.
 - The planned speakers for this review are Mark Ito (physics overview
   and needs), DSC (FDC design), Simon (FDC R&D, measurements, and
   algorithms), and David (GEANT3 simulations).
 - We had a planning meeting just after this FDC meeting to begin to
   review the status of the talks and other preparations and results
   that are needed both for this review and the March chamber review.
   Talk versions will be posted soon for all to see.

FDC Insertion and Cabling

 - During the collaboration meeting there was some discussion on having
   the FDC cabling come the upstream end of the solenoid magnet instead
   of the downstream end.  We had a separate meeting of the relevant
   folks last Friday.  Fernando has been working on defining the impacts
   and relocating the electronics racks for the different detector

Space Plan Request

 - Elke asked us to prepare a space plan request for the FDC construction,
   testing, and storage.  Brian and DSC will come up with a plan to
   circulate for feedback.

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.