Difference between revisions of "Minutes-9-20-2012"

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== Production ==
 
== Production ==
  
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- Dave: we started working on two new cathodes  
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- Dave: we started working on two new cathodes, #72 and #73, using the last two sets of foils (new foils are coming November/December). Casey and Tina finished stringing today the new wire frame #29. There was a small delay with the new g10 wire frames (Vision Machine didn't have the vacuum pump), but they promised to have the first frame by Monday.
  
−
- Lubomir: we may try to fix the wire frames #27 and #28 that are drawing high current. Suspect the via of the HV trace that connects the bottom trace just against the Rohacell. If this is the problem, can be fixed by drilling a hole from the back side. Bill agreed and we will try it next month when we will have time.
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- The first three cells of package #1 were assembled Monday-Tuesday using the standard Viton+Apiezon technique. Since then it's being flushed with gas. Oxygen goes down very fast, now it's about 1000ppm and expect it to be ~300ppm tomorrow so Vlad will start testing the package.
  
 
== Cathode corrosion ==
 
== Cathode corrosion ==
  
−
- On Monday we started a test with a cathode (the demo one) using two techniques to protect the copper from corrosion: one side lightly coated with Hysol, the other with Kapton films sitting on Apiezon. We installed this cathode in a cell with Viton+Apiezon and started flushing with gas at 200ccpm (to have enough flow through the oxygen sensor). Some leakage was found (< 10^-4) at the Kapton side but that pressure inside is very high due to the higher flow rate per cell. Interestingly leakages were found at the two transition regions between the Kapton and Hysol areas, probably the Hysol layer is thicker than the Kapton film. Importantly, the oxygen went down to 180ppm in three days.
+
- We tried several techniques for covering the cathodes but all they had some problems:
  
−
- We will wait till Monday to see the final oxygen percentage and will open the test package. If everything is OK we want to use the Hysol technique for the first half of the first package. Bill wanted to know if Dave is happy with the Hysol coating, then they discussed how to improve the flatness of the Hysol layer. In any case we will practice more before working on the production cathodes. Bill also proposed to use conformal coating instead of Hysol, but Eugene and Lubomir didn't agree since it introduces new material and there are complains from drift chamber groups about possible out-gassing. Even we have some parts of the PCBs coated inside the gas volume and we try to find the same material, we still need to do long tests
+
# Kapton film + Hysol: many wrinkles, bubbles. Bill said he could do this using vacuum bagging, but should be done before the foils are stretched on the frame. 
−
before we are sure it will not harm the chamber. As for the other technique, using Apiezon on big areas it's messy and not possible to clean, it may start leaking at higher temperature when chamber is in vertical position?
+
# Kapton film + Apiezon: the O-ring made a channel into the grease and the surface outside of that channel was elevated due to the grease covered with the film. The O-ring compression was low, several leaks were found especially between the foils. Still the oxygen went down to 75ppm for a cell with a cathode half covered with this method.
 +
# Hysol only: the epoxy layer that was applied was too thin (~0.5mil) so that it doesn't protect the copper efficiently. That was tested in the vacuum chamber were we saw copper discoloration with the Vition+Apiezon+Hysol sample, similar the the sample without Hysol.
  
−
- Vlad started a new test in the vacuum chamber now adding a sample with Viton+Apiezon against cathode foil that was coated with Hysol. The chamber will stay at very high temperature (close to 100deg C) and 100% humidity till Monday.
+
- Vlad
  
 
== Engineering ==
 
== Engineering ==

Revision as of 17:20, 20 September 2012

September 20, 2012 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
  2. Cathode corrosion (Lubomir, Vlad)
    • Cathode protection tests
    • Recent SEM results [1], [2], [3], [4]
  3. Engineering (Bill)
  4. Electronics (Chris, Nick)
  5. Third package tests FDC E-log (Beni, Lubomir)
  6. TDR, pages 132-143 (Lubomir)
  7. Other


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