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February 10, 2011 FDC meeting


  1. Production (David)
    • Blue Crab status
  2. Electronics (Fernando, Chris, Roger)
    • Rigid-flex assemblies
    • Foil production status
    • Other
  3. Engineering (Bill, David, Lubomir)
  4. Full-scale prototype studies (Lubomir)
  5. Other


Participants: Bill, Tina, Dave, Chris, Simon, Beni, Fernando, Eugene, Mark, Casey, Mike, and Lubomir. Tina Mann is our new FDC technician.


- Dave: 80% of the staff was moved to Blue Crab. Remaining are the stringing system and the Lazy Susan table. All the stuff will be cleaned before moving inside the clean room. There were again power problems at Blue Crab. As a result all the systems for the clean room went off and were reset later.

- Next steps at Blue Crab: gluing and laminating PCBs to the wire frame, then cutting/gluing foils and building cathodes. We need the expertise of Mark and Brian. Dave will make approximate schedule for these operations so that we can ask for their help ahead of the time. Bill: not sure what is the best glue for the lamination.


- The thickness of the rigid board of the rigid-flex assemblies was modified according to Roger's e-mail, but Bill found in the actual file that it was not. Roger was not there to clarify. Lubomir will contact Roger also regarding the foil production status.

- Bill and Dave had questions to Fernando about the solder to be used for the wires. Two solder types were used for the test wire plane: the solder recommended by Fernando and the solder paste used to tin the cathode contacts. It was easier to work with the later, while the use of the first one resulted in too thick solder layer. Fernando doesn't recommend the solder paste: corrosive and also more difficult to clean the flux. Fernando and Chris will look for a thinner solder wire.


- Bill is working on several modifications of the stringing system:

  • protector cover for the wires needed during the soldering,
  • modification of the pin rail to correct for the pitch that is ~250 microns off,
  • monuments to be attached to the granite table and the strongback (three on each) and will be used as reference points to align the strongback to the wire positions,
  • tool to be used for taping the wires down.

- Lubomir showed results for the position and tension measurements (page 551) on the first (test) wire plane built at JLab. First plot: deviation from the nominal position vs nominal position. It shows 1) a slope that can be explained by an angle of 25mrad (as shown on the second plot) of the measurement direction, or by a pitch bigger than 5mm; 2) there's jump in the positions close to the middle of the chamber, a result of one pitch being off by ~250microns (as measured with a micrometer), the change of the pitch is the same for the field and sense wires. We discussed what is the best way to correct for the offset: to cut and re-adjust the pin jig, or just to build a new pin jig. Bill will discuss it with the machine shop people.

- Tension measurements of all the wires of the test wire plane are shown at the bottom plot at page 551. Generally the tensions of the shortest wires deviate from the mean which can be explained by not using the right length, or other effects like the edge of the board affecting the vibrations. As Bill predicted, we found that the epoxy itself is not strong enough to keep the tension especially on the field wires. We were able to measure the tensions only after soldering the wires. The other problem was that the tension of the sense wires were 50% higher. After the meeting Lubomir found it was his fault, just using wrong density for the sense wires. The picture that is linked above is now the correct one.

- A new type of conductive glue came from CMU used in the CDC and we will try it soon. Beni: it is used at different places in the straws but they don't measure the conductivity of the connections. Curtis: Correction, CMU measures that each straw is electrically connected to its donut after the glue has cured. What is not measured is the connection from the donut to the endplate as the risk in damaging the inside of the straw is larger than the risk of the donut to feed-thru to endplate connection being problematic. We also note that the glue joint is not conductive until after the glue has cured for 24 hours.

Full-scale prototype tests

- Lubomir showed few more plots (bottom two plots on page 550) demonstrating how the ratio top/bottom strip signals changes over the plane for the individual wires. On the bottom chamber the effect (if any) is much smaller. We discussed different ways of troubleshooting the problem: changing the flow in the chamber in different ways, measuring the pressure in the chambers, disassembling the ground/cathode plane package.