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May 19, 2011 FDC meeting


  1. Production (Dave)
    • Cathodes
    • Wire planes
    • End windows: epoxy problem
  2. Engineering (Bill)
  3. Electronics status(Fernando, Chris)
  4. Chamber testing (Beni)
  5. Other


Participants: Eugene, Bill, Dave, Chris, Simon, Beni, and Lubomir. The meeting was in B101 due to the N* workshop.


- Dave: the set-up for gluing the rigid-flex assemblies is ready; today we will start gluing the assemblies on the first two production cathodes. The set-up was tested today with one flex glued then removed and then glued again. Two other cathode planes were glued, one of them tensioned and the frame glued on it.

- On one end window the epoxy didn't cure, but a sample from the same epoxy (and the left part in the cup) did cure. We suspect the surface was contaminated. Eugene: it's possible the epoxy was not mixed good enough. Also the surface on the end window is the only surface on the g10 frames that is not machined, and it is very smooth. On the second end window done in the same way the epoxy cured better. Most likely it was a contamination problem: we cleaned better the second end window. For the future production we will sand the surface of the frame.

- Two wires were broken on the first production frame while removing it from the strong-back. Bill will make a tool that separates the frame from the strong-back. The encoder on the motion stage doesn't work and most likely it is the bulb on the encoder head to be blamed. It is an old model, so if we need an encoder we have the replace the whole device. For the first production wire frame we didn't use the encoder; the stepper motor resolution was good enough. The pin rail is now at Vision Machine for fixing and hopefully will be back later today. After that we can fix the two wires. Then we will start stringing the second wire frame which is ready.


- The vibrations at Blue Crab were investigated on Saturday by Kirk Davis. He used an accelerometer connected with an analyzer and measured the vibration frequencies at different places (see the above link). On the sensor (also table, strong-back) he observed the same frequency (~39Hz) as on the AC unit and on the supporting beam, also on the walls but not on the floor. So, most likely the source is the AC coupled to the stringing table acoustically. Bill suggested putting plastic plates on the ceiling and improving the supporting beam. Eugene insisted that first we have to check if this is the reason for the problem with the wire sensing (10-20% of the field wires are not seen by the laser) and then to try to reduce the vibrations.

- Report from Olga (linked above) shows some contaminated spots on the filed wires. For the first report she did before, she cleaned the field wire samples ultrasonically and maybe that's why she didn't see the contamination before. It's not critical for the field wires to have some contaminated spots, also we may have to clean them with the ultrasonic cleaner before stringing. This is another possible explanation for the field wire sensing.


- Chris: we got the first 50+50 (tinned, not tinned) rigid flexes populated. We will build one cathode with tinned and one with not-tinned flexes.

Chamber testing

- The full-scale prototype was disconnected and is ready to be transported to Blue Crab, as soon as Dave finds a van, Friday or beginning of next week. We have now the mounting jig plate that will be installed in the dark room at Blue Crab. We will need also two round tables and a cart there (Dave will take care). Beni will re-collect the stuff needed for the test. Bill will help purchasing the piping and the connectors from the above list.

- Beni did some studies of the timing with fADC125 and he gets ~1ns resolution. He uses Gerard's interpolation procedure. At the end Eugene, Simon and Beni discussed the advantages/disadvantages of using fADC125 for the wires instead of F1TDC. Basically fADC will help for the pattern recognition, while with F1TDC one can achieve much better timing resolution. So, the answer will depend on the background rates and Simon and Lubomir will work on this.