Minutes-8-2-2012

August 2, 2012 FDC meeting

Agenda

1. Cathode corrosion
   • Status
   • Testing chambers small-scale test, vacuum chamber test
2. Production Construction Tracking (Dave)
   • Extra cathode production
   • Fixing corroded cathodes
   • Second package refurbishment
   • Grounding scheme (Vlad)
3. Engineering (Bill)
4. Electronics (Chris, Nick)
5. Test set-up in 126 (Beni)
6. Other

Minutes

Participants: Bill, Eugene, Dave, Nick, Chris, Simon, Beni, Vlad, and Lubomir

Cathode corrosion

- Bill: Olga is doing FTIR (Fourier Transform InfraRed) studies, that give information not only about the elemental composition but also about the bonds between the elements. She's looking at used and unused EPDM samples and there's some difference but the interpretation of the FTIR results is difficult. It will be also interesting to look at the copper samples and also Epoxy samples (Epon and Epolite) if possible with this method. Tim proposed to use pressure paper to look if the EPDM O-ring fills the grove and apply more pressure on the sides of the groove.

- Vlad (also with the help of his dad who's chemist) studied the literature about the copper corrosion. Normally as a first step copper reacts with watter (moisture) CO2 and O2 forming hydrides of Cu2O (copper oxide) that has redish color (Cu2O is good conductor). On the next step due to again water and sulfur (or chlorine) copper salts are formed like CuSO4, CuS and CuO (copper monoxides, mono-sulfides) having black/gray color what we are actually seeing, which are moderate conductors. Especially hydrogen sulfate is dangerous, we can identify it with lead acetate paper that we have ordered. Important is also that carbon serves as catalyst. We see that the EPDM O-rings leave carbon traces very easily.

- Three testing chambers are being considered: one with production wire frame and cathodes is running under HV for more than a week, it has both EPDM and Viton O-rings inside. Second test is with the small-scale prototype, that will have similar materials inside as explained in the document above: same EPDM, Viton, same wires (deadened already), Epon epoxy. Tomorrow we will have all the O-rings needed and will start that test, as well. Vlad proposed another test using a vacuum chamber (that didn't work to remove the bubbles from the epoxy) and his scheme is linked above. The idea is to increase the temperature (with a lamp) by 10-20degC resulting in 3-6 times speeding up of the corrosion. We will also increase the humidity inside the chamber. The test will be done without HV so far.

Production

- Dave showed the latest Construction Tracking file (linked): now refurbishing second package. The plan is to use all the spare cathodes there plus three newly build: all of them using new foils and one spare cathode frame (the only we had), and two refurbished (type-1 and type-2). The refurbished frames came from package #1 by successfully removing the foils. For package #1 we may use some of the cathodes from package #2 that didn't have bad channels (indicated with blue color) and some (or all) of the spare foils left after building package #2.

Other

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