Minutes-8-23-2012

August 23, 2012 FDC meeting

Agenda

1. Production Construction Tracking (Dave)
   • Cathodes
   • Third package
2. Cathode corrosion
   • Results from SEM analyses: [1]
   • Test chambers
3. Engineering (Dave)
   • Cathode strong-backs
4. Electronics (Chris, Nick)
   • PCBs
5. TDR, pages 132-145 (Lubomir)
6. Other

Minutes

Participants: Fernando, Tim, Eugene, Dave, Simon, Vlad, and Lubomir

Production

- Dave: working on 10 new cathodes to be used in the first package, not in the second package as we always stated before. Again the bottleneck is the card gluing, but we will start making progress there, by tomorrow we plan to have the cathode strong-backs ready to be used to move the cathodes. Will start working soon on the other two cathodes that are needed to finish the first package. After that we will have two sets of cathode foils left.

- The third package is ready with the subsystems: grounding, cooling tubes, HV cabling. The plan is to move it to 126 tomorrow. The grounding worked fine, Vlad put ~100 clips for grounding as planned and another ~100 attached close to both sides of the cards (where possible and needed) to prevent the cathode deformation at the periphery. As Casey suggested, we used a new method to install the cooling tubes. We tightened the bracket on one card in the middle of the tube and installed the rest of the brackets loose. Then, going from the middle card toward the two ends of the tube we tightened the rest of the brackets. Thus, the copper tubes apply some pressure on the cards; before we had problems with some of the cards being pulled by the tubes. Gluing of the back brackets with green epoxy to the tubes was done at the end. In 126 after installing the cables we should experiment how easy will be to remove the extra clips we put on the card sides.

Cathode corrosion

- New SEM results from Olga (follow the above link) for the samples from the Vlad's test with the vacuum chamber; the chamber had water inside and the temperature at end of the day (lamps were off overnight) was close to 100degC. The test was done for about 4 days:

• Copper foil with EPDM inside: significant corrosion, a lot of sulfur present.

• With the EPDM of the gasket, part of the foil strips were inside the gas chamber and part exposed to the air: no sulfur seen at the air side and a lot of it at the gas side. However, inside the gas volume there was moisture and the temperature was much higher than outside. We had seen corrosion before also in the samples placed in air with some water put on the foils and no heating. We will do more tests.

• Copper foil with Viton: some traces visible, almost no sulfur there but some chlorine.

• With Viton and Apiezon: no visible corrosion, only copper and carbon lines are visible, but the grease was not cleaned. Olga will repeat the measurements after cleaning it.

- The first testing chamber with production wire frame and cathodes was opened yesterday, exactly 4 weeks operating with HV and gas. Some traces from the EPDM O-ring are visible but it doesn't look like the corrosion on the first and second packages. We conclude that the humidity is an important factor. No traces on the cathode against the Viton+Apiezon O-ring are visible. The test with the small-scale prototype is running two weeks, haven't opened it yet.

- Tim for the humidity conditions in the Hall: nominally it will be less than 45%, but he can't exclude some periods when it might be higher. There will be dry air blowing through the magnet. We should avoid opening the Hall doors for a long time during the installation.

Engineering

- Discussions how to make sure the cathode stays flat during all the operations after installing the conductive tapes, which includes: gluing the cards to the back of the cathode frame, moving the cathode from one place to another, storing the cathodes, cathode installation in the package, colling tube installation, testing the cathode channels, connecting the cables to the cards.

- After the meeting Bill, Dave, Lubomir and Casey discussed these issues at Blue Crab. Bill will make two strong-backs (lifting frames) with suction caps (use vacuum), to be used on the foil or the back side of the cathode for transportation. Casey will work on a table with rods to store the cathodes in flat position. Same clips that are used for grounding will be put on both sides of the cards attaching them to the wire frame, which will prevent radial deformation during tube installation, cabling and testing.

- Bill: Mylar gluing problem we had recently is due to humidity. Several tests were done showing much better results when using lamps for heating. Bill suggested using lamps from now on the improve the curing process.

Electronics

- It turned out wrong Gerber files were used for the production of the extra 4 PCB sets ($9K). Eugene will discuss with the administration how to exclude such mistakes in the future; he suggested manufacturing another 4 PCB sets.

TDR

- Lubomir: the version linked above is almost complete; just sub-system section needs more work. Everybody is encouraged to make his remarks.corrections by the next meeting.

Other

- Beni asked when the third package will be in 126 for testing. Need to install the grounds, all the parts are ready, Vlad will start working on that, then the cooling tubes have to be installed and finally Chris will do the HV connections - in about 2 weeks must be ready.

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