Minutes-2-17-2011

February 17, 2011 FDC meeting

Agenda

1. Production (David)
   • Blue Crab status
2. Electronics (Fernando, Chris, Roger)
   • Rigid-flex and foil production status
   • Other
3. Engineering (Bill, David, Lubomir)
   • Lessons learned from the test wire plane FDC Log Book, page 551
   • Wire stringing modifications
   • Other
4. Chamber testing
   • Plans for full package tests (Beni)
   • Tests with the middle chamber (Lubomir)
5. Other

Minutes

Participants: Bill, Mark, Dave, Chris, Simon, Beni, and Lubomir.

Production

- Dave: the stringing table and the cathode tensioning system are the only main items not yet moved to Blue Crab. The stringing table will be modified before moving there: 6 holes in the granite have to be drilled and different other new pieces mounted there. Will have three computers in the clean room, one new and another two used, all Windows. The temperature in the clean room is lower than the required one and the vendor will fix the problem tomorrow. It turned out the temperature control is not in the clean room and we are not supposed to use it.

- The plan for the next month work at Blue Crab includes: cathode frame inspection, building PCB rings, cutting, aligning, and gluing cathodes. We will start with old PCB and damaged cathode foils and then use the new/good ones. The ultimate plan is to build parts for one chamber that has to be tested before the mass production.

- Dave's working on the procedures/travelers, we can't start production without these documents.

Electronics

- Chris: 50 cables were reworked, but 13 of them came short by a foot. It turned out those are CDC type cables. Even if the length is not critical, we decided not to accept such cables for the FDC. Simon was concerned that we need a plan how to bundle, run the cables. Bill has some preliminary drawings, but everybody agrees that this is important.

- The rigid-flex will be produced as it was in the first article. We requested additional 140 flexes to be used for exercising and as spares in case of cathode foil failure. In total we will have 640 flexes.

Engineering

- There was a long discussion what we have learned from the stringing:

1. Bill questioned if the wire vibration (used in tension measurement) is the reason for the several broken wires between the epoxy and the solder. Suggested using computer to control the amplitude and frequency of the generator. Dave will try connecting to the generator with LabView. Lubomir thinks that the wires broke by the leads while trying to keep them on the solder. The use of conductive rubber (from Fernando) will prevent this because one can put them away from the soldering pad.

Bill suggested using

1. Bill wants to try soldering before gluing. Lubomir: without glue before soldering, it will be difficult to cover the wires to prevent from solder balls, without touching the wires.

- 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.

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